Search

ZnO semiconductor offers many advantages as an electron transport layer (ETL) in photovoltaic-based devices, including high charge carrier mobility and hole-blocking ability. In this work, ZnO thin film is introduced as an ETL between (Bi 0.93 Gd 0.07)FeO 3 (BFO7Gd) ferroelectric and ITO thin film to form ITO/ZnO/BFO7Gd/Au heterostructure. The device with the ETL exhibited a superior photoresponsivity than the one without ETL, reaching ∼32% enhancement. Furthermore, a subsequent E -field poling on the ITO/ZnO/BFO7Gd/Au heterostructure resulted in an additional ∼25% increase in photoresponsivity. The enhancement is mainly attributed to two factors: (1) high electron mobility and lower recombination rate resulting from the introduction of ZnO ETL, and (2) efficient charge separation facilitated by the polarization-driven internal E field that superimposes with the interfacial built-in E fields. The introduction of ZnO ETL and the utilization of the ferroelectric polarization prove to be an alternative route to further modulate the photosensing performance of BiFeO 3 -based near-UV photodetectors. [ABSTRACT FROM AUTHOR]

The sufficient material selection of electron transport layer (ETL) enormously promises exceptional conversion efficiency from perovskite (PVT) solar cells (PSCs), which in turn give rise to their rapid establishment in world-wide photovoltaic (PV) market. Among the tactics exerted on ETLs, and thus, intensifies the adequacy of associated PSCs, the methodology of doping stands productive. Therefore, this research validates the implementation of such effectual ETLs on widely approved methyl ammonium lead triiodide (MAPbI 3)–based PSCs. The work brings together two versions of zinc oxide (ZnO) ETLs: one in its pristine form, and the other is aluminum (Al) co-doped with silver (Ag) represented as Ag-AZO. The investigation launches the PV capabilities of Ag-AZO ETL against its undoped correspondent. Accordingly, the earlier part of the investigation centers on the experimental assessment of ZnO and Ag-AZO nanoparticles (NPs) affirming their material and morphological aspects. Later, the research deals with the involvement of both NPs as ETLs signifying the PV potential of MAPbI 3 –based PSCs through comprehensive numerical analysis. The judgements of investigation declare that MAPbI 3 –based PSC with Ag-AZO ETL yields a desirable power conversion efficiency (PCE) of 27.26 % against 25.98 % from the control cell. The investigation will definitely enlighten the development of forthcoming efficient PSCs incorporated with appropriate multiple metals co-doped ETLs. • Ag and Al co-doped ZnO (Ag-AZO) nanoparticles were synthesized using solution process. • The potential of Ag-AZO electron transport layers of perovskite solar cells was validated through numerical analysis. • By applying an Ag-AZO layer, an exceptional efficiency of 27.26 % was accomplished. [ABSTRACT FROM AUTHOR]

• Introduction of low-temperature undoped and 1–3 wt% lithium (Li) doped sol–gel-derived ZnO (LZO) and utilized them as ETLs in PbSe QDSCs. • The solution of the Li-doped ZnO was obtained by the addition of LiCl into ZnO sol–gel with a Li/Zn molar ratio of 1%, 2%, and 3%. • LZO-based QDSCs exhibit the highest PCE of 10.80% with an FF of 69.50%, open-circuit voltage (Voc) of 0.62 V, and current density (Jsc) of 27.67 mAcm−2 when doped with 2%. • The photoelectric properties (Voc , Jsc , FF, and PCE) were almost unchanged after 40 days. The lead selenide quantum dots (PbSe QDs) have incredible features because of their tunable bandgap and synthesis process at low temperatures. Aside from the highly effective QDs active layer, the electron transport layer (ETL) also plays a significant part in obtaining high-efficiency colloidal quantum dots solar cells (CQDSCs). Here, we introduce undoped and 1–3% lithium-doped zinc oxide (LZO) sol–gel as an ETL and utilized it in CQDSCs to achieve high efficiency. ZnO and LZO thin films are obtained by low annealing temperature whereas the PbSe QDs-based absorber layer is deposited by layer-by-layer (LBL) technique in the presence of 1-ethyl-3-methylimidazolium iodide (EMII) which is acting as a ligand exchange material. Results show that 2 wt% Li-doping on one hand can maximumly increase the conduction band minimum, and transmittance, whereas on the other hand decreases the oxygen defects densities as well as the roughness of the thin film as compared to other ETLs. Subsequently, PbSe CQDSCs with 2 wt% Li-doped ZnO ETL display the highest power conversion efficiency (PCE) of 10.80% as compared to 10.12% PCE of ZnO-based PbSe CQDSCs (7.5% higher). Similarly, 2 wt% LZO-based PbSe CQDSCs devices show long-term stability of about 40 days. Furthermore, Li-doping in ZnO offers a viable approach for low-cost, high-performance CQDSCs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Organic solar cells (OSCs) are great for internet of things because these work with versatility and can be used both indoors and outdoors. • Inverted configuration makes OSCs more stable and efficient than the conventional one. • Successful exploration of ZnO and Ga-doped ZnO based electron transport layer (ETL) for improved light harvesting by inverted OSC. • Fine-tuned doping concentration in ZnO yield 10.96 % and 4.95 % power conversion efficiency under 1-sun and 1000 lx halogen. • Ga-doping in ZnO improves the photostability of OSC by decreasing oxygen vacancies and retarding its formation under sustained light exposure. Organic solar cells (OSCs) are gaining attention for powering Internet of Things devices due to their impressive power conversion efficiency, flexibility, and slim designs suitable for both indoor and outdoor. The focus on inverted-structured OSCs is increasing due to their superior stability compared to conventional OSCs. This study investigates the use of inverted OSCs with electron transport layers (ETL) made from ZnO and Ga-doped ZnO for light harvesting. OSCs were fabricated using PM6:ITIC-4F as the active layer, and the impact of ZnO doping (Ga) concentration was examined under 1-sun and 1000 lx halogen. Optimizing the doping concentration significantly improved device performance, with PCE values of 10.96 % and 4.95 % for optimally doped ZnO under 1-sun conditions and halogen lamps, respectively. A comparison of photostability under 1-sun and 1000 lx halogen, with varying light soaking durations (0–240 min), showed that Ga-doping in the ZnO ETL improved photostability by reducing oxygen vacancies and slowing down their formation during continuous light exposure. This decrease in oxygen vacancies and enhancement of grain boundaries positively affected charge transport, leading to higher PCE. In summary, Ga-doped ZnO ETL in inverted OSCs demonstrates improved performance and photostability, making them promising for various light harvesting applications. [ABSTRACT FROM AUTHOR]

ZnO is well-known electron transport material; however, its charge carrier mobility is restricted due to lower conductivity and hysteresis losses. To overcome these issues, 1–3 wt% Mg-doped ZnO nanofibers were synthesized via electrospinning and then applied as electron transport layer (ETL) of perovskite solar cell. The structural, morphological, chemical composition, electronic structure, and optical activity of the synthesized nanofibers were studied to elucidate the role of Mg doping. X-ray diffraction of all nanofibers revealed that Mg was successfully incorporated into ZnO lattice and revealed that ZnO is present in hexagonal wurtzite structure. Optical characterization of the nanofibers revealed that with an increase in Mg2+ doping concentration, the bandgap energy (Eg) tuned from 3.36 eV to 2.8 eV. It was observed that doping ZnO matrix with Mg ions improved the electronic structure, hence favoring the increase in the fill factor, current density, and efficiency. By doping 1, 2, and 3 wt% Mg into ZnO, efficiency was increased up to 8.48, 10.33, and 13.52%, respectively. Thus, a significant improvement in the performance of ZnO was noted by our proposed facile Mg doping. In addition, a significant improvement in photocatalytic activity was observed in Mg doped ZnO, which was used for fabrication of antibacterial textiles. [ABSTRACT FROM AUTHOR]

ZnO quantum dots (QDs) with average particle size of 4.4 nm were prepared using a low temperature processing solvothermal route. ZnO QD based thin films were then prepared from the ZnO QD based solution using spin coating technique and annealed at 250, 350 and 450 °C. The average grain size and energy band gap of ZnO were respectively increased and decreased from 5.5 to 22.9 nm and 3.37 to 3.27 eV upon increasing the annealing temperature up to 450 °C. The photoluminescence analysis showed that the as-coated ZnO film and ZnO film annealed at 250 °C have high density of oxygen vacancies; these defects were reduced upon increasing the temperature to 350 and 450 °C. The photoelectric properties of the films were strongly affected by the grain size and the defects present in the films. The photo-to-dark current ratio (PDCR) was decreased from 3723 to 371%, whereas the responsivity was increased from 1.25 to 218 mA/W with the increase of temperature to 450 °C. As-coated and 250 °C-annealed films exhibited better photoresponse than others in terms of PDCR, rise time and fall time due to their larger surface-to-volume ratio, making them promising candidate as electron transport layer in perovskite solar cells. [ABSTRACT FROM AUTHOR]

Fig : (a) Schematic illustration of IOSC, (b) J-V characteristics of spray deposited GZOs as the ETL in IOSCs. [Display omitted] • Fabrication of highly transparent and conducting GZO film by spray technique. • Effect of DC voltage during the spray deposition of GZO films. • GZO thin film used in inverted organic solar cells (IOSCs) as electron transport layer (ETL). • GZO deposited under DC voltage of 2000V showed the PCE of 6.5% in IOSCs. • Low-cost environment friendly GZO can be effectively used as ETL in IOSCs. The electric field-assisted spray deposition of highly conducting and transparent gallium doped zinc oxide (GZO) films, with noticeable improvement in optical, structural, and electrical properties, is reported for application in organic photovoltaics with superior device performance. The GZO films deposited with applied voltages of 0 and 2000V to the nozzle exhibited an improved electrical resistivity of ∼1.8 × 10−3 Ω-cm and a transmittance (in the visible region) of over 80% for the films deposited under electric field, which can be used as electron transport layer (ETL) in inverted organic solar cells (IOSCs- ITO/GZO/PTB7:PC 71 BM/MoO 3 /Ag). Improved photovoltaic performance (power conversion efficiency: 6.5%) is obtained for the IOSC devices fabricated GZO ETL with the applied voltage of 2000V in comparison to the device fabricated using GZO ETL with the applied voltage = 0V (power conversion efficiency: 5.8%). [ABSTRACT FROM AUTHOR]

Abstract Optimizing electron transport layer (ETL) is a key issue to guarantee the performance of polymer solar cells (PSCs). In this work, by passivating ZnO with a naphthalimide-Schiff base (NS) as ETL, the inverted PSCs with polythieno[3,4- b ]- thiophene- co -benzodithiophene (PTB7): [6, 6]-phenyl-C 71 -butyric acid methyl ester (PC 71 BM) as the light harvesting layer (LHL) exhibited enhanced device performance. Studies demonstrated that the NS introduction passivates the surface defects of ZnO thus suppressing exciton quenching, resulting in enhanced exciton dissociation, efficient charge carrier collection and reduced loss of charge recombination, and thereby giving high power conversion efficiency (PCE). While the PCE of the inverted PSCs with pure ZnO ETL is 7.34%, that of the devices with NS passivated ZnO (NS-ZnO) ETL shows an enhanced PCE of 8.20% (∼11.7% improvement). More importantly, the NS-ZnO can be facilely obtained by adding NS into ZnO precursor, suggesting a simple and efficient way to enhance the PSCs performance. Graphical abstract This work identifies naphthalimide-Schiff passivated ZnO electron transport layer would dramatically improve the performance of inverted polymer solar cells. Image 1088 Highlights • A newly naphthalimide-Schiff base NS was synthesized. • Formation of composite ETL was obtained by adding NS in ZnO precursor. • Polymer solar cells based NS passivated ZnO ETL shows an enhanced PCE of 8.20%. • Introduction of NS optimized exciton dissociation, charge carrier collection and charge recombination. [ABSTRACT FROM AUTHOR]

A new universal electron transport layer that involves doping hydrogen-plasma-treated tungsten disulfide (WS 2) nanosheets into ZnO for polymer/fullerene or small molecule organic photovoltaics (OPVs) was prepared. A hydrogen plasma treatment was used to alter the structures of WS 2 nanosheets such that the W6+ content was converted into W4+; then ZnO:WS 2 nanosheets composites were prepared to form electron transport layers (ETLs). The energy band of the ZnO:WS 2 films could be tuned from 5.15 to 4.60 eV by varying the concentration of the WS 2 nanosheets up to 0.5 wt%. It was found that ZnO:WS 2 ETLs exhibited superior charge transport properties than those of the pristine ZnO layer because of the structure changes, as determined from the X-ray scattering characterizations. OPVs incorporating active layers of PTB7-TH/PC 71 BM and PTB7-TH/IDIC blends exhibited their power conversion efficiencies of 10.3% and 6.7%, respectively, with the incorporation of 0.3 wt% of the WS 2 nanosheets, up from 8.9% to 5.4% for the corresponding devices featuring pristine ZnO—relative increases of 16% and 24%, respectively. This study demonstrates the effectiveness of hydrogen plasma treatment for altering the surface structures of two-dimensional transition-metal-dichalcogenide nanosheets, and paves a way for the composite electron transport layers for use in organic photovoltaics. Image 1 • Using N 2 quenching exfoliate of bulk WS 2 into nanosheets, and modifying the surface of nanosheets with hydrogen plasma treatment. • Incorporating plasma-treated WS 2 nanosheets into ZnO to form a composite ETLs for enhancing its electron mobility. • Tuning the LUMO of the ZnO:WS 2 composite film from 5.15 to 4.6 eV by varying the concentration of the WS 2 nanosheets. • Using the ZnO:WS 2 composite ETLs for enhancing the PCE of OPVs involving PTB7-TH with PC 71 BM or IDIC acceptor systems. [ABSTRACT FROM AUTHOR]

Abstract In this study, we realized an inverted polymer solar cell by depositing Al-doped ZnO (AZO) through room temperature radio-frequency magnetron sputtering as an electron transport layer (ETL) between an organic PTB7 and PC 71 BM mixture active layer and indium tin oxide (ITO) transparent electrode. The crystal structure of the AZO thin films changed as the Ar gas pressure was varied. X-ray diffraction showed that the highest crystallinity was obtained at 70 mTorr. Further experiments were carried out to determine the optimum thickness. An AZO film deposited on a glass substrate with a thickness of 100 nm had an average visible-light transmittance of 83.3% and an electrical resistivity of 6.6 × 10−3 Ω·cm. The power conversion efficiency (PCE) showed no significant difference with regard to thickness, and ranged from of 7% to 8%. The 100-nm AZO thin film had the highest PCE of 7.87%, which is approximately 90% higher than that of the sample without an ETL. Graphical abstract Image 1 Highlights • AZO thin films were optimized by RF magnetron sputtering. • AZO thin films with high crystallinity were obtained at room temperature. • AZO thin films were applied for PTB7:PC 71 BM blend-based PSC as an ETL layer. • Thickness dependent PCE was analyzed by measuring the J-V curve of the PSCs. • The PSC with the 100-nm AZO thin film had highest PCE of 7.87%. [ABSTRACT FROM AUTHOR]

The transport layer materials play a key role in the performance of organic solar cells (OSCs) as they facilitate the movement of charges from the photoactive layer to the selective electrodes. The presence of vacancies and morphological defects in it poses challenges and leads to losses in device performance. Therefore, this study investigates the morphology, structural, and optoelectrical properties of Zinc Oxide (ZnO) and Tris-(8-Hydroxyquinoline) Aluminium (Alq3) for application as electron transport layer (ETL) in OSCs. ZnO nanoparticles (NPs) were synthesized using a low-temperature solvothermal method, while the Alq3 microparticles were prepared separately. Nanocomposite thin films were fabricated through the spin coating technique. Experimental results revealed that a 1:1 ratio of ZnO NPs:Alq3 demonstrated improved structural, surface passivation, and optical properties with high transmission of over 70 %. In addition, ZnO NPs:Alq3 exhibited negative nonlinear absorption coefficient (β) and refractive index (n 2) values with a susceptibility (χ(3)) of about 10−5 esu. Furthermore, electrical measurements confirmed favorable n-type characteristics, excellent electrical conductivity, and higher photocurrent in ZnO NPs:Alq3 thin films compared to the pristine thin films. Overall, this research underscores the potential of ZnO:Alq3 nanocomposites as efficient ETLs in OSCs. • Investigated properties of ZnO NPs:Alq3 as ETL in organic solar cells. • ZnO NPs:Alq3 thin films are prepared by spin coating. • Improved electron transport and conductivity of ZnO NPs:Alq3 are evident. • ZnO NPs:Alq3 ETL is promising in OLEDs, solar cells, and photodetectors. [ABSTRACT FROM AUTHOR]

Highlights • Hf-In-ZnO (HIZO) as electron transport Layer for inverted organic solar cells (iOSC). • Twice lifetime of encapsulated HIZO-iOSC vs. currently used PFN-iOSC. • Reduced S-shape deformation in the JV curves of HIZO-iOSC vs. PFN-iOSC. Abstract In this study, we report the use of Hafnium-Indium-Zinc-Oxide (HIZO) as electron transport layer (ETL) in inverted organic solar cells (iOSCs) using a bulk heterojunction of Poly({4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl}{3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl}) (PTB7) and [6,6]-phenyl C71 butyric acid methyl ester (PC 70 BM) as active layer. The absorption spectrum and performance parameters obtained are compared to those obtained for similar iOSCs where the ETL was poly [(9,9-bis (30- (N,N-dimethylamino) propyl) -2,7-fluorene) -alt-2,7- (9,9-dioctylfluorene)] (PFN). Initially, devices showed the S-shaped current–voltage curve that has been modeled using a three-diode equivalent circuit model. This phenomenon can be removed by repeating electrical sweep-cycles under illumination. The degradation under nitrogen atmosphere and under encapsulation was also analyzed and compared with the degradation of the iOSCs using PFN. It was observed that the degradation of encapsulated HIZO-iOSC was twice slower than that of PFN-iOSCs. This increase in stability can be attributed to the Hf atoms, which have a stronger thermodynamic tendency to form metal oxides, suppressing the dissociation of HIZO. [ABSTRACT FROM AUTHOR]

Abstract A novel ternary hybrid material zinc oxide & polyethyleneimine ethoxylated: reduced graphene oxide (ZnO&PEIE:RGO) is fabricated, and then used as electron transport layer (ETL) to improve the performance of inverted polymer solar cells (iPSCs). Compared with the pure ZnO as ETL, the power conversion efficiency (PCE) of iPSCs based on P3HT:PCBM blend system with ZnO&PEIE:RGO as ETL is efficiently improved from 3.00% to 3.83%. The addition of RGO increases the conductivity of ZnO, and the addition of PEIE not only passivates the surface of ZnO nanoparticles to reduce its surface defects, but also prevents the aggregation of the precursor dispersion of ZnO:RGO. Moreover, the performance of the PTB7:PCBM based iPSCs with ZnO&PEIE:RGO as ETL is also improved from 6.91% to 8.87% compared with that of the device with pure ZnO as ETL. Interestingly, devices with ZnO&PEIE:RGO also exhibit enhanced lifetimes devices with ZnO, which still retain up to 63% of their original PCE after stored for 30 days without any encapsulation in air. Consequently, this novel ternary hybrid material ZnO&PEIE:RGO is a promising ETL material for PSCs. Graphical abstract Image 1 Highlights • A novel ZnO&PEIE:RGO nanocomposite is prepared by an in-situ synthesis method. • The addition of RGO improves the electrical conductivity of hybrid ETL. • The mixture of PEIE passivates the surface defects of hybrid ETL. • The performance of the iPSCs with ZnO&PEIE:RGO as ETL is obviously improved. • More interesting, the device with ZnO&PEIE:RGO as ETL has a long-term stability. [ABSTRACT FROM AUTHOR]

In this study, suspended zinc oxide nanoparticles were used as the electron transport layer in trans-perovskite solar cells. The perovskite film was prepared by a liquid two-step method, and the crystallinity, surface morphology, and optical and photoelectric properties of the perovskite films were then investigated. The results showed that the crystallinity and film compactness of the perovskite could be controlled by the stoichiometric quantity and the perovskite formation rate. Moreover, the film morphology was affected by the annealing temperature, duration, and the amount of toluene solvent, which could be leveraged to enhance the efficiency of the device due to the charge trapping defect. The optimal annealing temperature and duration were 80 °C and 10 min, and the optimal volume ratio of isopropyl alcohol to toluene was 9:1. The highest performing perovskite solar cells in this study exhibited an energy conversion efficiency of 15.78%, a short-circuit current of 20.80 mA/cm 2 , an open circuit voltage of 1.10 V, and a fill factor of 0.69. [ABSTRACT FROM AUTHOR]

• Perovskite films are deposited on ZnO ETLs by one-step spin-coating. • The modification of the amino compounds reduces the contact resistance of the ZnO and improves the quality of MAPbI 3 films. • The optimal device based on isobutylamine (IBA) modification shows high power conversion efficiency of 18.84%. n-Type zinc oxide (ZnO) has high electron mobility, good light transmittance, and a suitable work function and is considered to be a suitable electron transport material in perovskite solar cells (PSCs). However, the chemical compatibility between ZnO and perovskites is poor, making it difficult to prepare highly efficient and stable PSCs by a one-step spin coating method. Here, the ZnO surface is modified with three amino compounds, butylamine (BA), isobutylamine (IBA) and 2-amino-2-methyl-1-propanol (AMP). Three amino compounds can react with 3D perovskite to form a thin and more stable perovskite with a 2D structure, which can improve the stability of ZnO-based PSCs fabricated by one-step method. Interestingly, the conductivity of amine-modified ZnO is also improved due to the presence of amino (NH 2) and hydroxyl (OH) groups which can induce the dipole polarization. The modification of amino compounds on the surface of ZnO can affect the hydrophilicity of ZnO surface that is related to the crystallization of perovskite film. Devices with IBA modification exhibit improved stability, and the power conversion efficiency (PCE) can reach 18.84%. Therefore, we provide a new strategy to improve the surface of the ZnO electron transport layer for high-performance PSCs fabricated by a one-step method. [ABSTRACT FROM AUTHOR]

• Nitrogen-doped graphene/ZnO nanorod composite (NG-ZnO NR) was used as electron transport layer (ETL) to replace TiO 2 for perovskite solar cells. • NG-ZnO NR composite based perovskite solar cells achieved a highest efficiency (16.82%) as compared to pristine ZnO nanorods (12.87%). • NG-ZnO NR composite promotes formation of uniform perovskite thin films with a high surface coverage area in comparison to pristine ZnO nanorods. • NG-ZnO NR composite based perovskite solar cells exhibited improved photocurrent and photon to electron conversion efficiency due to enhancement in light absorption. We demonstrate for the first time, the photovoltaic performance of perovskite solar cells (PSCs) by employing nitrogen-doped graphene/ZnO nanorod nanocomposites (NG-ZnO NR NCs) as an electron transport layer (ETL). A series of PSCs are fabricated by varying the NG concentration from 0 to 1 wt% with an increment of 0.2 wt% in ZnO NRs having a device structure of FTO/NG-ZnO NR NCs/CH 3 NH 3 PbI 3 /Spiro-MeOTAD/Ag. The perovskite films grown on NG-ZnO NR NCs exhibited a uniform film with high surface coverage area with an improved crystallinity. By employing photoluminescence measurements, it was found that NG-ZnO NR NCs reduced the interfacial resistance by improving charge carrier extraction, which is in correlation with an improvement in photocurrent and fill factor in the corresponding devices. At an optimized concentration of NG (0.8 wt%) in ZnO NRs, PSCs obtained an improvement in photocurrent from 17.38 mA/cm2 to 21.98 mA/cm2 and the power conversion efficiency from 12.87% to 16.82%, respectively. [ABSTRACT FROM AUTHOR]

• ZnO:PEI nanocomposite was developed as electron transport layer for use in OSCs. • Higher stability of ZnO:PEI ink stored under ambient conditions more than 6 months. • Improved mechanical properties of the ZnO layer replaced by ZnO:PEI film. • Less thickness dependence for ZnO:PEI as electron transport layer fabricated by roll-to-roll printing. Large-scale roll-to-roll (R2R) micro-gravure printing is one of the most effective fabrication techniques to achieve the commercialization of organic solar cells (OSCs). In the high-performance OSC devices, the electron transport layer (ETL) plays an important role. In this paper, a composite ink of ZnO and polyethylenimine (PEI) was developed to fabricate large-area ETL for the inverted OSCs through R2R micro-gravure printing. It was found that the modification of ZnO nanoparticles by PEI effectively improved ink stability and enhanced the mechanical property. Using R2R micro-gravure printing, the thickness and coverage of the ZnO: PEI films were well regulated through changing the printing roller speed and web speed. Consequently, a high-power conversion efficiency around 6% was obtained for the flexible PTB7-Th: PC 71 BM device with the thickness of R2R printed ZnO: PEI layer up to 120 nm, demonstrating the high printability of this ZnO: PEI composite material for the use in printed flexible OSCs as the interface layer. [ABSTRACT FROM AUTHOR]

ZnO nanoparticles (NPs) are widely employed as the electron transport layer (ETL) material in quantum dot light-emitting diodes (QLEDs) due to their excellent electron transport properties and inherent stability. However, the unbalanced carrier injection caused by the redundant electron injection is a common phenomenon existing in QLEDs with ZnO ETL. Here, based on the lower electron mobility and shallower lowest unoccupied molecular orbit (LUMO) of most organic electron transport ·materials than ZnO NPs, we report a strategy to modulate the electron transporting properties of ZnO NPs by doping organic small molecular electron transport materials. Several kinds of small molecular dopants including LiQ (lithium 8-quinolate), TPBi (1,3,5-tris(N-phenylbenzimidazol-2,yl) benzene), and BPhen (4,7-diphenyl-1,10-phenanthroline) are separately introduced to modify ZnO. The resulting device with LiQ-doped ZnO ETL at a doping ratio of 7 wt% exhibits the optimal performance at peak current efficiency (CE) and external quantum efficiency (EQE) up to 8.07 cd/A and 7.74%, which are about 1.93- and 1.94-fold higher than 4.19 cd/A and 3.98% of the device with pristine ZnO ETL, respectively. The improvement of performances can be mainly attributed to the inhibition of electron injection and interfacial exciton quenching by the use of LiQ-doped ZnO ETLs. This work may offer a promising method for fabricating high performance QLEDs and promote their application development in the display fields. Image 1067 • Doping organic small molecules into ZnO nanoparticles electron transport layer (ETL). • The doped ZnO ETLs help to impede the superfluous electron injection. • The interfacial exciton quenching effect can be suppressed by the use of LiQ-doped ZnO ETL. • The red QLEDs based on LiQ or TPBi-doped ZnO ETL all possess the improved performances. [ABSTRACT FROM AUTHOR]

The excellent adhesion property of polydopamine (PDA) provides a new way to fixing nanoparticles. This study investigated the effects of PDA/ZnO nanocomposite as an electron transport layer (ETL) material on the performance of polythieno[3,4-b]-thiophene/benzodithiophene:[6,6]-phenyl-C70-butyric acid methyl ester bulk heterojunction solar cell. On one hand, the strong adhesive property of PDA to ZnO nanoparticles is beneficial to the formation of a uniform ZnO thin film, which is favorable for electron transfer. On the other hand, an energy level mismatch exists between PDA and ZnO, which hinders electron transfer from ZnO to ITO. Upon optimization, filling factor and photoelectric conversion efficiency are improved by 23.2% and 13.8%, respectively, when the single ZnO layer is replaced by PDA/ZnO nanocomposite as the ETL. Open circuit voltage resulted in 9.8% enhancement from 0.61 V to 0.67 V. However, the short circuit current density is reduced. [ABSTRACT FROM AUTHOR]

A ZnO-Ge bilayer was proposed as an electron transport layer (ETL) in inverted ternary organic solar cells (OSCs). The energy level alignment, surface morphology, optical and electrical properties, and interface charge transfer were investigated to understand the impact of the additional Ge NPs layer. The results indicated that apart from improving the energy level alignment, the Ge NPs layer optimizes the interfacial contact between the active layer and ETL. Moreover, the ZnO-Ge bilayer shows better optical transmittance and perpendicular electrical transport properties compared to that of ZnO NPs layer. Benefit from the enhanced charge transfer from the active layer to ETL, the champion power conversion efficiency (PCE) was significantly increased to 9.15% by introducing the additional Ge layer, which exhibited a 18.4% improvement compared to that of the ZnO-only devices. Our results demonstrated the feasibility of ZnO-Ge bilayer as the ETL for high-performance OSCs. [ABSTRACT FROM AUTHOR]

This work introduces a new light-harvesting architecture using different weight ratios of 0.01, 0.03 and 0.05 wt% of one-dimensional tube-like graphitic carbon nitride (1D g-C 3 N 4) additives blended with ZnO (GT1, GT3 and GT5) as electron transport layer, prepared by high energy ball milling approach. The ZnO nanoparticles are synthesized by Caesalpinia pulcherrima plant extract and act as a reducing and capping agent. The tube-like structure g-C 3 N 4 material is prepared by treating melamine material with ethylene glycol (EG) at 550 °C. The morphological, optical, and structural properties of the prepared photovoltaic materials are analyzed by Field emission-electron microscopy (FE-SEM), Transmission electron microscopy (TEM), Ultra Violet-Visible spectroscopy (UV–Vis), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) instruments. The simple and cost-effective approach is followed to fabricate planar perovskite photovoltaic for an active area of 1 cm2 under ambient conditions. The additives present on the ZnO layer reduce the surface defects and improve electron extraction and light-harvesting behaviour. Also, the champion device (GT3) shows a maximum power conversion efficiency of 12.22 % as compared to all the fabricated devices under open-air atmospheric conditions. Ambient stability and UV-stability analysis of all the fabricated devices are estimated for 360 h and 20 h duration. These 1D g-C 3 N 4 additives modified ZnO-based perovskite photovoltaics can be utilized for optoelectronics applications. [Display omitted] • The 1D g-C 3 N 4 additive material was prepared via thermal decombustion approach. • 0.03 wt% g-C 3 N 4 additives modified ZnO layer achieved a PCE of ~12.22 % under ambient condition. • Ambient stability and UV-stability analysis were carried out for 360 h and 20 h. [ABSTRACT FROM AUTHOR]

• Mg-doped and ZnMgo-coated shell of ZnO NPs were synthesized using the sol-gel method. • The performance of QLED devices using Mg-doped ZnO NPs as ETLs was significantly improved, achieving a maximum EQE of 6.0 % and a maximum current efficiency of 8.2 cd A−1. • The device performance was further improved by utilizing Mg-doped and ZnMgO-coated ZnO NPs as ETL, which achieved a maximum EQE of 9.0 % and a maximum current efficiency of 11.5 cd A−1. ZnO nanoparticles (NPs) are considered the most promising materials for electron transport layer (ETL) in quantum dot light-emitting diodes (QLEDs). Herein, we employed a synergistic strategy of Mg doping and ZnMgO shell coating to modify the defect states and energy levels of ZnO NPs. Mg doping mitigated the exciton luminescence quenching caused by charge transfer. A ZnMgO shell was also applied to coat the Mg-doped ZnO (ZMO) NPs to passivate surface oxygen defects further. Consequently, QLEDs utilizing ZMO@ZnMgO ETL demonstrate external quantum efficiency and maximum current efficiency of 9.0 % and 11.5 cd A−1. This work shows an effective defect passivation strategy to enhance the performance of red-emitting InP-based QLEDs. A coordinated strategy of Mg doping and ZnMgO shell coating was employed to modify the defect states and energy levels of ZnO nanoparticles to improve the performance of red-emitting InP-based QLEDs. With Mg doping, the conduction band minimum of ZnO NPs shifts upward, which reduces the electron accumulation at the QD/ZnO interface and mitigates exciton luminescence quenching caused by spontaneous charge transfer at the interface. Additionally, a ZnMgO shell was applied to coat the Mg-doped ZnO (ZMO) NPs to passivate surface oxygen defects and improve the luminescence efficiency of the QLED devices. As a result, QLEDs utilizing ZMO@ZnMgO ETLs demonstrate an external quantum efficiency of 9.0 % and a maximum current efficiency of 11.5 cd A−1, which are approximately 2.4-fold higher than those of the devices with ZnO ETLs. [Display omitted] [ABSTRACT FROM AUTHOR]

A simple low-temperature solution-processed zinc oxide (ZnO) and aluminum-doped ZnO (AZO) were synthesized and investigated as an electron transport layer (ETL) for inverted polymer solar cells. A solar cell with a blend of poly(4,8-bis-alkyloxy-benzo[1,2-b:4,5-b′] dithiophene-alt-alkylcarbonyl-thieno [3,4-b] thiophene) and (6,6)-phenyl-C71-butyric acid methyl ester as an active layer and AZO as ETL demonstrates a high power conversion efficiency (PCE) of 7.36% under the illumination of AM 1.5G, 100 mW/cm 2 . Compared to the cells with ZnO ETL (PCE of 6.85%), the PCE is improved by 7.45% with the introduction of an AZO layer. The improved PCE is ascribed to the enhanced short circuit current density, which results from the electron transport property of the AZO layer. Moreover, AZO is a more stable interfacial layer than ZnO. The PCE of the solar cells with AZO as ETL retain 85% of their original value after storage for 120 days, superior to the 39% of cells with ZnO ETL. The results above indicate that a simple low-temperature solution-processed AZO film is an efficient and economical ETL for high-performance inverted polymer solar cells. Due to its environmental friendliness, good electrical properties, and simple preparation approach, AZO has the potential to be applied in high-performance, large-scale industrialization of solar cells and other electronic devices. [ABSTRACT FROM AUTHOR]

Abstract Photostability of the polymer solar cells (PSCs) remains a challenge to attain, as number of factors including the electron transport layers contribute to the degradation of PSCs when they are tested under 1 sun illumination, along with heat and humidity. Especially electron transport layers (ETLs) have considerable contribution to the overall degradations in these solar cells. Most studied ETL into the fabrication of inverted PSCs is zinc oxide (ZnO) yet the photostability of these PSCs is limited. This degradation most probably occurred due to the direct contact of zinc metal with the photoactive layer. This interface between ZnO and photoactive layer results in the initiation of degradations in PSCs. Keeping in view of this issue, we have modified the ZnO ETL by mixing ZnO nano particles with ethoxylated polyethyleneimine (PEIE) and then passivating this modified ZnO (m-ZnO) with ultrathin PEIE buffer layer. The power conversion efficiency is not affected by this approach, but when PSCs were subjected to 1 sun illumination, these m-ZnO/PEIE based PSCs have shown the enhanced light soaking (LS) stability. These findings indicate that optimizing the interface between the photoactive layer and the electron transport layer can lead to enhanced LS stability. Highlights • Ethoxylated polyethylenimine (PEIE) passivated ZnO (m-ZnO) as electron transport layer (ETL). • The direct contact of ZnO with photoactive layer is avoided. • The m-ZnO/PEIE layer help in enhanced light soaking (LS) stability. • The m-ZnO/PEIE layer has nitrogen enriched surface. • The nitrogen enriched ETL surface contributes to enhanced LS stability. [ABSTRACT FROM AUTHOR]

Inorganic n-type metal oxide materials, i.e., ZnO have been developed and employed as interface layers for energy level matching and electron transport in order to achieve high performance perovskites based optoelectronic devices. In this work, we successfully apply atomic layer deposition (ALD) technique to deposit ZnO directly on top of CsPbBr 3 to serve as the electron transport layer. A regular perovskite light emitting diode (PeLED) in a configuration of glass/ITO/PEDOT:PSS/CsPbBr 3 /ZnO/Ag was fabricated. In the CsPbBr 3 emitting layer, polyethyleneimine ethoxylated (PEIE) dissolved in an anti-solvent chlorobenzene (CB) was introduced to assist the nucleation and crystal growth of perovskite films, as well as providing surface reactive sites for ALD deposition of ZnO layer particularly. The ALD deposition temperature on the growth, crystallinity and morphology of ZnO and subsequent device performance was investigated. We obtained PeLEDs of the best performance with the best current and external quantum efficiency (EQE) of 0.49 cd/A and 0.14%, respectively, which is as 14 folds high as an inorganic CsPbBr 3 device using F8 as the electron transport layer reported previously. [ABSTRACT FROM AUTHOR]

In this work, we demonstrate the use of annealed sol-gel derived ZnO nanoparticles acting as electron transport layer (ETL) in inverted bulk heterojunction (BHJ) polymer solar cells (PSCs). We have examined the photovoltaic performance of devices based on poly(2-methoxy-5-(2-ethylhexyloxy)- p -phenylenevinylene) (MEH-PPV):(6,6)-phenyl-C61-butyric acid methyl ester (PC 61 BM) blend system employing the ZnO nanoparticles as an ETL with CuI as hole transport layer (HTL) in comparison to the case of using the conventional HTL of poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) sulfonic acid (PEDOT:PSS). The effect of the presence of another layer of ZnO macrospheres attached to the ZnO nanoparticles is also investigated. The highest power conversion efficiency (PCE) value of 1.35% was achieved for device: ITO/ZnO nanoparticles/MEH-PPV:PC 61 BM/CuI/Ag, which is 275% more the value obtained when CuI was replaced by PEDOT:PSS. The comprehensive analyses on structural and optical characteristics including SEM, XRD, FTIR, PL and UV–vis spectroscopy indicated that the use of the ZnO nanoparticles alone as ETL, together with the CuI as HTL could effectively reduce trap-assisted recombination and charge accumulation at the interface, which is beneficial for the enhanced device performance. [ABSTRACT FROM AUTHOR]

We have investigated ZnO thin films prepared via photochemical reaction as the electron transport layer (ETL) of inverted organic solar cells (OSCs). Morphological and electrical properties of the ZnO thin films prepared by the photosensitive ZnO sol were studied according to the annealing temperature and their effects on the performance of the inverted poly(3-hexylthiophene):phenyl-C61-butyric acid methyl ester (P3HT:PCBM) OSCs was characterized. It was found that the optimal annealing temperature of the ZnO thin films was 330 °C, and that devices with the ZnO ETL annealed at this temperature exhibited the largest short-circuit current density ( J sc ) of 9.39 mA/cm 2 , as well as the highest power conversion efficiency (PCE) of 2.31%, which can be attributed to enhanced electron transport and interfacial properties. Devices containing ZnO films formed at optimal annealing condition exhibited an open circuit voltage ( V oc ) of 0.60 V and a fill factor (FF) of 41.0%. However, further increase of the annealing temperature led to degradation of the device performance, despite further improvements in electrical properties. We have found that marked increase in the surface roughness of the ZnO films occurred at temperatures above 350 °C which could be detrimental to the OSCs characteristics due to a high contact resistance and a large leakage current. [ABSTRACT FROM AUTHOR]

An intermediated-band in Cr-doped ZnTe (ZnTe:Cr) thin films was analyzed and high performance intermediate-band solar cells (IBSCs) were fabricated with a high-quality ZnO:Al electron transport layer (ETL). The energy band structure and defect states of the ZnTe:Cr absorber layer by means of ultraviolet photoelectron spectroscopy and deep level transient spectroscopy were investigated, and then two defect levels, L2 and L4, are positioned 0.3 and 1.14 eV above the valence band. Especially, it was confirmed that the 1.14 eV activation energy of the L4 defects corresponds to the energy required to reduce Cr + to Cr 2+ , which these defects are responsible for the intermediate band observed in the ZnTe:Cr thin film. From the optical and electrical measurements, the ZnO:Al thin film grown under the partial oxygen pressure (p(O 2 )) of 1 mTorr show high mobility, low resistivity, and few antisite oxygens defects. Finally, the ZnTe:Cr IBSC with ETL of ZnO:Al grown under 1 mTorr p(O 2 ) showed photoelectric power conversion efficiency of 8.13%. [ABSTRACT FROM AUTHOR]

• Glass/ITO/ZnO-ZnMgO (nano)/PCBM/CH 3 NH 3 PbI 3-x Cl x /PEDOT: PSS/C3-SAM/Ag based hybrid organic solar cell is fabricated. • Efficiency of 14.7% is achieved. • ZnMgO nanorods are textured and passivated using a simple chemo-thermal process, post-thin-film growth. • Demonstration of use of CH3-SAM and ZnO/ZnMgO nano thin-films to substantially improved the solar cell efficiency. This paper represents perovskite material based hybrid (ITO/ZnO-ZnMgO (nano)/PCBM/CH 3 NH 3 PbI 3-x Cl x /PEDOT: PSS/C3-SAM/Ag) organic solar cell with high quantum and power conversion efficiency. Due to the insertion of 3-aminopropanoic acid as an ambipolar self-assembled monolayer (C3-SAM) and ZnO/ZnMgO layer carrier collection efficiency increases. An optical modified structure is proposed (through the modification of ZnO/ZnMgO layer) to increase the surface to volume ratio and enhance the photon collection efficiency. As a result, the Internal quantum efficiency (IQE) increases 83.2% to 91.7% fill factor (FF) changes from 77% to 85%, short circuit current density (J sc) changes from 14.9 mA/cm2 to 21 mA/cm2, and overall solar cell efficiency increases from 9.17 to 14.7%. [ABSTRACT FROM AUTHOR]

The electron transport layer (ETL) plays an important role in the performance and stability enhancement of perovskite solar cells (PSCs). Zinc oxide is considered a cost-effective and low-temperature processed ETL for PSCs, which offers decent mobility. However, the interface reaction occurs via a reaction of zinc oxide with the organic-inorganic metal hybrid halide perovskite absorber, which results in the degradation of the PSCs. To overcome this issue, metal doping was carried out. However, metal doping causes a reduction in the transmittance of the zinc oxide ETL layer because of high absorption. Thus, the overall performance of the PSCs was reduced due to the lessening of the photogenerated current. In this regard metal co-doping (Mn and Co) was done to improve the electrical as well as electronic properties. Furthermore, the influence of Mn doping on the structural, optical, and photoluminescence properties of Mn x Co 0.015 Zn 1-x O (x = 0, 0.002, 0.008, and 0.012) hexagonal nanosheets was investigated. X-ray diffraction results revealed that the inter-planar spacing, cell parameters, unit cell volume, lattice strain, and dislocation density were maximum for the Mn content of 0.2%. The acquired values of the optical band gap (E g) are 3.39, 3.52, 3.58, and 3.18 eV for x = 0, 0.2%, 0.8%, and 1.2%, respectively. The corresponding absorption coefficient is reduced with increasing Mn content. The obtained refractive indices are 1.437, 1.402, 1.428, and 1.426 for x = 0, 0.2, 0.8, and 1.2%, respectively. The above results confirm that the Mn x Co 0.015 Zn 1-x O with x = 0.8% provides the lowest absorption and the highest value of bandgap. Thus, it can be the most suitable ETL for high-performance PSCs. The simulation results reveal that via applying MCZO ETL, the efficiency can be achieved over 23%. • New ZnO-based compounds (Mn x Co 0.015 Zn 1-x O) were synthesized via the Co-doping of Mn and Co into ZnO. • Influence of Mn doping in Co–ZnO (CZO) was investigated on some of the properties of ZnO. • Highest values of cell parameters were obtained for Mn doping of 0.2%. • The value of the absorption coefficient was reduced with increasing Mn content. • All the samples offer a refractive index value of less than 1.5. [ABSTRACT FROM AUTHOR]

Preparation of electron transport layer (ETL) with high uniformity by convenient and low-temperature process is of essential importance for the future development of colloidal quantum dot solar cells (CQDSCs) into large-area and flexible devices. Herein we utilized magnetron sputtering technique to deposit ZnO thin film as the ETL of PbS CQDSCs. The ZnO film deposited at ambient temperature displayed preferential growth along (001) direction, pinhole free morphology, and good optical transmittance. On rigid SnO 2 :F (FTO) conductive glass substrates, PbS CQDSCs with sputtered ZnO ETL achieved a power conversion efficiency of 6.47% under AM 1.5 G simulated solar irradiation, which was higher than the 6.02% efficiency of the CQDSC fabricated on the benchmarked ZnO nanocrystals ETL. The good uniformity of sputtered ZnO film also facilitated the consistency of photovoltaic parameters of big-sized CQDSCs, as demonstrated by the similar output of four series-connected CQDSC units fabricated in one batch with a total active area of 14.4 cm 2 . Flexible PbS CQDSCs was also fabricated on the sputtered ZnO ETL, using In 2 O 3 :Sn-coated polyethylene terephthalate (ITO-PET) as the substrate, which achieved a power conversion efficiency of 3.87% and displayed negligible decline of the photovoltaic parameters after 100-time bending treatment. Our research demonstrates that the magnetron-sputtered ZnO film, with favorable features of low-temperature process, large-area continuity, and high bending tolerance, presents promising potential for the future development of PbS CQDSCs. [ABSTRACT FROM AUTHOR]

Organic photodetectors with bulk heterojunctions were constructed with a structure of ITO/ZnO/P3HT:PC 61 BM/MoO 3 /Al. The effect of the thickness of the ZnO layer on the properties of the device were investigated by fabricating photodetectors with different ZnO layer thicknesses: 20, 40, 50, 60, and 80 nm. The 40 nm-thick ZnO electron transport layer provided the device with a low dark current density (1.7 × 10−9 A/cm2), high specific detectivity (2.7 × 1013 Jones), wide linear dynamic range (78.9 dB), and fast response speed (τ r / τ f = 0.61/0.75 μs). The results show that an optimal thickness of the ZnO electron transport layer can effectively block hole injection into the active layer, which is a promising strategy to improve the performance of organic photodetectors. • Change defect concentration by simple spin coating. • Low dark current density with 1.7 × 10−9 A/c m2. • High specific detectivity 2.7 × 1013 Jones. • Detect a wide light intensity range with 78.9 dB. • Fast response speed with τ r / τ f = 0.61/0.75 μs. [ABSTRACT FROM AUTHOR]

Ga-doped ZnO(GZO) is investigated as an electron transport layer in organic solar cells based on a promising donor: acceptor system of poly[(5,6-difluoro-2,1,3-benzothiadiazol-4,7-diyl)-alt-(3,3‴-di(2-octyldode-cyl)-2,2′; 5′,2″; -5″,2‴-quaterthio-phen-5,5‴-diyl)] (PffBT4T-2OD):phenyl-C71-butyric acid methyl ester (PC 70 BM). With the inverted geometry having a configuration of ITO/GZO (40 nm)/PffBT4T-2OD:PC 70 BM (270 nm)/MoO 3 (20 nm)/Al (100 nm), maximum power conversion efficiency (PCE) of 9.74% has been achieved, while it is limited at 8.72% for devices with undoped ZnO. Our study based on the structural, morphological, compositional, and electrical characterizations indicate that suggests enhanced device performance of the GZO-based devices resulted mainly from the improved electrical properties of Ga-ZnO thin films as compared to undoped ZnO. [ABSTRACT FROM AUTHOR]

An organic-inorganic hybrid electron transport layer (ETL) is developed using benzyl viologen dichloride (BV–2Cl) as a dopant for the preparation of sol-gel ZnO precursor solution. The inverted polymer solar cells (I–PSCs) based on PTB7-Th:PC 71 BM were prepared by introducing hybrid ZnO:BV-2Cl as ETL, and the effect of BV-2Cl on the photovoltaic performance of PSCs was closely investigated. Consequently, the device with hybrid ZnO:BV-2Cl (1% wt%) as ETL achieves the power conversion efficiency (PCE) of 9.31%, which is 16.5% more efficient than the device using pure ZnO as ETL. As the results indicate, hybrid ZnO:BV-2Cl films can modulate the interfacial compatibility of the hydrophilic surface of conventional ZnO films, hence enhancing charge transport and exciton dissociation. Our results indicate that using BV-2Cl as a dopant for the preparation of ZnO ETL is a facile and efficient method of fabricating high-performance I–PSCs. [Display omitted] • The hybrid ZnO:BV-2Cl have been successfully exploited in PSCs as electron transport layer (ETL). • The interface contact between cathode and active layer was improved after adding BV-2Cl into ZnO. • The device with hybrid ZnO:BV-2Cl ETL achieves the PCE of 9.31%. [ABSTRACT FROM AUTHOR]

Poor long-term stability of perovskite solar cells (PSCs) in ambient air has hindered the PSC commercialization. In this work, we introduce an ionic liquid (IL) of 1-ethyl-3-methylimidazolium hexafluorophosphate ([EMIM]PF 6 ) as an inter-layer between the ZnO and perovskite layers. The devices are fabricated in air without any atmosphere controlling. Solar cell with a power conversion efficiency of 13.50% is obtained, and a small J-V hysteresis is accomplished. More importantly, after 90 days (>2000 h) storage in air, our device without encapsulation retains 88.17% of its initial efficiency. Our work provides a simple valid strategy to develop air-processed, stable and efficient PSCs for future applications. [ABSTRACT FROM AUTHOR]

The objective of this study was to comprehensively investigate and compare PCBM/ZnO and C 60 /BCP-based electron transport layers (ETLs) (well recognized as representative ETLs) between perovskite and metal electrode in perovskite solar cells (PeSCs) for high-performance p-i-n structure PeSCs. Their film characteristics and their effects on solar cell performances were studied. When PCBM/ZnO was used as ETL material, the PCE of PeSCs was 19.36 %, which was higher than the PCE of 17.10 % when C 60 /BCP was used possibly due to more efficient charge recombination reduction and charge extraction shown in PCBM/ZnO-based devices. However, in terms of stability (air, light-soaking, and heat), C 60 /BCP-based devices showed higher stability than PCBM/ZnO-based devices. • A higher PCE was obtained in PCBM/ZnO (19.36 %) than that of C 60 /BCP (17.10 %). • C 60 /BCP shows better stability than PCBM/ZnO. • The selection of an appropriate ETL is important in terms of stability and efficiency. [ABSTRACT FROM AUTHOR]

Organic-inorganic solar cells (PSCs) are considered emergent photovoltaics (PV) technology. For better performance and stability of the PSCs, the selection of the electron transport layer (ETL) is vital. In this study, Cd doped ZnO (CZO) nanoparticles (NPs) are synthesized using the solution process. The optical properties of the CZO NPs were determined experimentally. With Cd doping, the optical bandgap was reduced and the lowest bandgap was obtained for 2% Cd doping. With further increase of Cd doping concentrations, the bandgap was slightly increased. However, the highest values of refractive index were obtained for Cd doping of 1%. The optical parameters were used to simulate the n-i-p (FTO/ETL/MAPbI 3 /HTL/Au)-structured PSCs using gpvdm solar simulator. The simulated parameters viz. short circuit current density (J sc), open circuit voltage (V oc), fill factor (FF), and power conversion efficiency (η) of the CZOs-based PSCs were compared with the parameters obtained for ZnO ETL. An efficiency of 26.07% was achieved for PSC with 1% Cd-doped ZnO, which is 9.72% higher than the efficiency of ZnO-based PSC (η ∼ 23.76%). These experimental results proved an opportunity to improve the performance of the PSCs via Cd doping. • The optical simulation was carried out to predict the influence of Cd doping in ZnO on performance perovskite solar cells. • The short circuit current density was enhanced by 9.5% via Cd doping. • The best efficiency of 23.76% was achieved for Cd doping of 1%, which was 9.72% higher than the undoped ZnO. [ABSTRACT FROM AUTHOR]

Zinc oxide (ZnO) grown on indium tin oxide (ITO) glass substrates were decorated with bismuth sulfide (Bi 2 S 3) nanorods by thermal decomposition of bismuth ethylxanthate precursor method. Different thicknesses of ZnO/Bi 2 S 3 bilayer films were prepared by controlling the spin speed of bismuth xanthate precursors (5000, 6000 and 7000 rpm, respectively) and applied as the electron transport layer (ETL) in organic solar cells (OSCs) with the structure of ITO/ZnO/Bi 2 S 3 /PM6:Y6/MoO 3 /Ag. The effects of different thickness of ZnO/Bi 2 S 3 as ETLs on device performance and stability were investigated in detail. Firstly, the device based on ZnO/Bi 2 S 3 6000 rpm as ETL confirmed excellent performance with the power conversion efficiency (PCE) of 12.50%, which was improved by 28.60% of the reference device without Bi 2 S 3 nanorods coated. XRD and SEM results showed that Bi 2 S 3 nanorods covered the ZnO surface well. Electrical conductivity and the current density-voltage (J-V) curve results under dark conditions showed that when Bi 2 S 3 nanorods were added between the active layer and ZnO, the interfacial conductivity can be effectively increased and improved the interfacial carrier transport efficiency. Secondly, the stability results of the ZnO/Bi 2 S 3 6000 rpm device demonstrated that the PCE of ZnO/Bi 2 S 3 6000 rpm device was maintained about 91.54%, while that of pure ZnO as ETL was maintained about 75.26% of the original value after 33 h in air. This means that the ZnO/Bi 2 S 3 prepared by thermal decomposition of the bismuth xanthate precursor on ZnO is a promising electron transport material in OSCs. • ZnO/Bi 2 S 3 films were applied as the electron transport layer in solar cells. •Bi 2 S 3 layer was fabricated by thermal decomposition of bismuth ethylxanthate. •The efficiency and stability of devices were improved using ZnO/Bi 2 S 3 films. [ABSTRACT FROM AUTHOR]

ZnO thin films (s-ZnO) were prepared by an in-situ solution process instead of traditional nanocrystalline ZnO (n-ZnO). By optimizing the technological conditions, ZnO thin films with better energy level matching and better transmission performance were prepared (annealed at 180°), and s-ZnO was applied to perovskite LED for the first time to achieve high-performance luminescence. This work reduces the complexity of ZnO process in PeLED device preparation and provides a good strategy for the commercialization of perovskite LED. [Display omitted] • In-situ solution-processed ZnO ETLs were fabricated from zinc acetate dihydrate in 2-methoxyethanol by spin-coating technology. • The performance of S-ZnO PeLEDs is similar to that of n-ZnO based devices with peak efficiency of around 22%. • Compared with traditional ZnO nanocrystals, S-ZnO is easier to prepare. As an alternative method of the electron transport layer (ETL) of Zinc Oxide nanoparticles, an in-situ solution process was developed to prepare ZnO thin films for manufacturing perovskite light-emitting diodes (PeLEDs). After optimizing the processing conditions, the band energy and electron mobility are adjusted appropriately, which shows advantages to balance the carrier injection in PeLEDs. The near-infrared PeLEDs with ZnO film prepared by in-situ method demonstrated external quantum efficiency of 22%, which is compatible with their counterpart using ZnO nanoparticles. Our report provides a feasible strategy for the low-cost fabrication of PeLEDs with high performance. [ABSTRACT FROM AUTHOR]

Highly uniform one-dimensional ZnO nanoarrays (ZnO NAs) fabricated by hydrothermal process were successfully explored as electron transport layer (ETL) for offering a direct and efficient path for electron transport in inverted polymer solar cells (PSCs). The inorganic CdS shell layer by in situ growth on the ZnO NAs surface was used to passivate and repair the surface defects of ZnO NAs. To further engineer the ZnO surface and improve the compatibility between ETL of inorganic ZnO/CdS core/shell and polymer blend contact junction, those organic molecules of 3,6,7,10,11-pentakis-(hexyloxy)-2-hydroxytriphenylene (TP-OH), 1-pyrenol (Py-OH) and 4′-(7-hydroxy-heptanoyl)-biphenyl-4-carbonitrile (BP-OH) were respectively spin-coated on the ZnO NAs/CdS surface to fabricate ETL based on ZnO/CdS/TP-OH NAs, ZnO/CdS/Py-OH NAs, ZnO/CdS/BP-OH NAs. The π–π interactions between the organic molecules and fullerene acceptors could lead to the well-organized distribution of active layer materials, which is in favor of the enhancement of electron selectivity and the reduction of recombination probability of electrons and holes. The incorporation of ZnO/CdS/Py-OH NAs as ETL into the inverted PSCs based on P3HT:PC 61 BM resulted in a superior power conversion efficiency (PCE) of 4.2% with enhanced short circuit current ( J sc ) and fill factor (FF), compared to 3.1% for bare ZnO NAs, due to the intermolecular close-stacking and relative stronger π–π interaction energy between Py-OH and fullerenes. In addition, the sensitized ZnO surface led to intimate interface between ETL and active layer, which would be in favor of increasing the stability of the device. [ABSTRACT FROM AUTHOR]

The carbon quantum dots (CQDs) with astonishing optical and electrical features have been utilized to improve the photovoltaic performance of organic solar cells (OSCs). In this work, CQDs dispersed in isopropanol were incorporated into photoactive layer of poly(3-hexylthiophene) (P3HT):(6,6)-phenyl-C61-butyric acid methyl ester (PC 61 BM) with different volume concentrations (0, 20, 40, 60 and 80 vt%). ZnO nanorod arrays, serving as the electron transport layer, was prepared on ZnO seed layer-coated fluorine-doped tin oxide (FTO) glass substrates. The CQDs-incorporated P3HT:PC 61 BM photoactive layers were then spin-coated on top of ZnO and silver (Ag), acting as the top electrode, was deposited via thermal evaporation method. It was found that 40 vt% CQDs-incorporated device demonstrated the highest power conversion efficiency and enhancement of 37% compared to that of the device without CQDs. It is proven that the introduction of CQDs improves the optical absorption, exciton dissociation and charge transport of the OSCs. [Display omitted] • CQDs-incorporated P3HT:PC 61 BM thin film was deposited as photoactive layer. • 37% increment in PCE was achieved with the introduction of CQDs. • The optical absorption, exciton dissociation and charge transport were enhanced. [ABSTRACT FROM AUTHOR]

A polyvinylpyrrolidone (PVP) thin film (9 nm) prepared on the top of Al-doped ZnO (AZO) electron transport layer by spin-coating, was developed as an interface modifier in inverted polymer solar cells (IPSCs). The PVP with excellent alcohol solubility provided a strong adhesion and wettability, leading to an improved interface quality between the AZO and active layer. Combined with a reduced work function of the AZO layer, the resulting devices showed a significant increase in power conversion efficiency from 2.86% to 4.08%, benefiting from the dramatic enhancement in fill factor (35%). Due to the ease of use and remarkable boost in efficiency, our results indicated that PVP was a promising candidate for surface modification material in IPSCs. [ABSTRACT FROM AUTHOR]

Abstract: We report that thermal annealing of P3HT:PCBM bulk heterojunctons (BHJs) on top of a commonly used sol–gel ZnO electron transport layer can lead to the formation of PCBM clusters, which significantly decreased short circuit current density (up to 45%), open circuit voltage (up to 35%), and fill factor (up to 15%). To understand the cause of this phenomenon, we deposited ZnO films using different sol–gel recipes and systematically studied the correlation between sol–gel ZnO processing and the morphology of the P3HT:PCBM BHJ. We showed that higher amounts of monoethanolamine (MEA), a stabilizer in the ZnO sol–gel precursor, lead to higher densities of PCBM clusters in the BHJ. In addition, we correlated the cluster area fraction with bimolecular recombination at 100mW/cm2, as quantified by white-light biased external quantum efficiency measurements. Finally, we show that rinsing off residual organics from the ZnO surface after pyrolysis eliminated PCBM cluster formation, avoiding poor organic photovoltaic device performance. [Copyright &y& Elsevier]

Black-phased cesium lead triiodide (γ-CsPbI 3) inorganic perovskite is one of the most desirable candidates for highly efficient perovskite solar cells (PSCs) due to its intrinsic thermal stability and solvable preparation. The electron transport layer (ETL) plays crucial roles of electron extraction/transport and hole blocking in the devices. Zinc oxide (ZnO) with superior electron mobility and suitable energy level is a promising electron transport material for inorganic PSCs, but adopting ZnO as an ETL in inorganic PSCs is barely reported at present. In this work, we present low-temperature processed ZnO as an ETL in γ-CsPbI 3 PSCs. The interesting phenomenon that the transition temperature of γ-CsPbI 3 formation on ZnO ETL decreased from 180 °C to 130 °C is observed. The well-matched lattices of ZnO and CsPbI 3 as well as nonexistent deprotonation which occurs in MAPbI 3 based PSCs indicate ZnO can be a suitable electron transport material for inorganic PSCs. A power conversion efficiency of 12.22% and a high open circuit voltage of 1.14 V are obtained because of the good energy level alignment and the surface contact. This work shows ZnO can be used as a promising ETL in inorganic PSCs. Image 1 • γ-CsPbI 3 perovskites are grown on ZnO under a low annealing temperature of 130 °C. • The device exhibits a PCE of 12.22% with a high V OC of 1.14 V. • Lattice match and low interfacial energy lead to a low transition temperature. • The good energy level alignment and surface contact result in high performances. [ABSTRACT FROM AUTHOR]

[Display omitted] • ZnO surface is successfully modified via nontoxic biomaterial (GHK-Cu). • The modification of GHK-Cu increase the conductivity of ZnO. • The polymer solar cells (PSCs) with new electron transport layer (ETL) are fabricated. • The power conversion efficiency (PCE) of PSCs with new ETL are obviously increased. • The physical mechanism of improving the performance has been deeply analyzed. The interfacial modification with biomaterials is an effective and environmental protection way to improve the efficiency of inverted polymer solar cells (IPSCs) by reducing the defects and interface recombination of ZnO electron transport layer (ETL). In this paper, ZnO surface is successfully modified via Gly-His-Lys-Cu (GHK-Cu), a nontoxic biomaterial, to fabricate novel ZnO&GHK-Cu composite film. The modification of ZnO surface by GHK-Cu makes the Zn-O-Cu bond formed on the surface of ZnO, which provides a channel for the electron transfer from electron-rich functional groups (such as carboxyl, amino and carbonyl) to Zn2+, the electron defects caused by the oxygen vacancies in the ZnO lattice are passivated, which is beneficial to the transfer and extraction of charges in IPSCs. Moreover, the modification of GHK-Cu decreases the chemisorbed oxygen of the surface of ZnO, the height of the Schottky barrier between the ZnO crystal grains is reduced, resulting in an increase in the conductivity of ZnO. The novel ZnO&GHK-Cu composite film has excellent photoelectric properties and IPSCs with new ZnO&GHK-Cu as ETL are fabricated for the first time. As the result, the IPSCs based on PBDB-T:ITIC with ZnO&GHK-Cu as ETL show an optimal power conversion efficiency (PCE) of 11.93%, increases by 15.6% in comparison with ZnO ETL-based IPSCs with a PCE of 10.32%. Meanwhile, the PCE of IPSCs based on PM6:Y6 increases from 14.66% to 16.46%. More interesting, the physical mechanism of improving the performance of IPSCs by modifying of ZnO surface with biomaterial has been deeply analyzed. The work provides an effective method for modification of ZnO surface, also shows that biomaterial GHK-Cu has application prospect in photovoltaic devices. [ABSTRACT FROM AUTHOR]

Abstract: A facile and cost-effective method is demonstrated to prepare a nano-porous rugged zinc oxide (ZnO) film without complicated processes and strict condition. A sol–gel derived ZnO is simply coated onto the substrate and subsequently removed the unreacted precursor and residual matters by solvent extraction. Thus, the precursor and residuals provide the vacancy to form a highly rugged surface. Compared with the flat ZnO film, the rugged ZnO is not only performs better purity than the flat film, but also increases the interfacial contact between the ZnO and bulk-heterojunction layer. By using the rugged ZnO as an electron transport layer, an enhancement of 20% in photocurrent generation could be achieved in an inverted poly(3-hexylthiophene):[6,6]-phenyl C61 butyric acid methyl ester solar cell together with highly air stability. [Copyright &y& Elsevier]

Abstract: This study evaluated the possibility of utilizing a spray-coating process for inverted organic solar cells (IOSCs). The performance and stability of the IOSCs with zinc oxide (ZnO) as the electron transport layer made by different processes, such as spray-coating, spin-coating and sputtering, were investigated. The IOSCs subjected to the spray-coated ZnO layer showed a power conversion efficiency of 3.17±0.11% under AM 1.5 simulated illumination and stability (>80% of its original efficiency after 30 days). The device performance and stability of the IOSCs with the spray-coated ZnO layer was compared with those of spin-coated and sputtering deposited layers. [Copyright &y& Elsevier]

Defects passivation in electron transport layer (ETL) is a key issue to optimize the performance of polymer solar cells (PSCs). In this work, a novel strategy is developed to form defects passivated ZnO ETL by introducing 4- tert -butylpyridine (TBP) agent into precursor. While the power conversion efficiency (PCE) of the inverted PSCs based poly{4,8-bis [(2-ethylhexyl)oxy]benzo [1,2-b:4,5-b']dithiophene-2,6-diyl-alt-3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno [3,4-b]thiophene-4,6-diyl}:[6,6]-phenyl C71-butyric acid methyl ester (PTB7:PC 71 BM) with the pure ZnO ETL is 8.02%, that of the device with modified ZnO ETL is dramatically improved to 10.26%, with TBP accounting for ~28% efficiency improvement. Our study demonstrates that the precursor agent significantly affect the surface morphology and size of ZnO in ETL. Furthermore, it proves that the ZnO ETL with TBP (T-ZnO) is beneficial to polish interfacial contact between ETL and active layer and depress exciton quenching loss, resulting in enhanced exciton dissociation, efficient carrier collection and reduced charge recombination, thus improving the device performance. To verify the universality of T-ZnO ETL, the champion photovoltaic performance with a PCE of 11.74% (10% improvement) is obtained in the PBDB-T-2F:IT-4F based nonfullerene PSCs using T-ZnO as ETL. Our work developed a new, universal and facile strategy for designing highly efficient PSCs based on fullerene and nonfullerene blend systems. Highly efficient fullerene and nonfullerene based polymer solar cells were achieved after application of 4- tert -butylpyridine passivated ZnO ETL. Image 1 • Use additive in ZnO precursor solution to prepare electron transport layer (ETL) was firstly reported. • The highest PCE of 10.26% and 11.74% were achieved in the PTB7:PC71BM and PBDB-T-2F:IT-4F based PSCs, respectively. • This ETL would improve interface contact, suppress exciton quenching and depress inside recombination loss. [ABSTRACT FROM AUTHOR]

This study elucidates a comparison between zinc oxide (ZnO) and zinc oxide:Polyethylenimine ethoxylated (ZnO:PEIE) nanocomposite as an electron transport layer (ETL). The impact of ZnO:PEIE annealing temperature to increase the fill factor (FF) and current density (J sc) of the devices was first studied after optimizing the doping concentration of PEIE. It was found that 0.4 wt% concentration and 150 °C annealing temperature of ZnO:PEIE ETL showed a superior performance for the devices. The introduction of PEIE promoted the charge transport by decreasing the work function of ZnO, which caused an improvement in the conductivity and current density of devices. For ZnO, the efficiency was 1.25%, which was enhanced to 1.46% with 0.4 wt% PEIE doping and further enhanced to 1.53% at 150 °C annealing temperature. The crystallinity of the ETL can be enhanced by choosing an effective annealing temperature that assists in increasing the current density and fill factor. This research work offers a desirable approach for the synthesis of high-performance organic solar cells. [ABSTRACT FROM AUTHOR]