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This study delves into the profound implications of employing an intensive xenon lamp treatment with a rapid curing method completed within 4 min, to fabricate a ZnO layer. Subsequently, we applied a coating of PM6:Y6 as the active layer and utilized MoO 3 /Ag as the contact electrode, aiming to advance the efficiency of polymer solar cells (PSCs) through entirely room-temperature processes. Our investigation juxtaposes this xenon lamp treatment with the conventional hot plate method for annealing the ZnO layer, conducted at 180 °C for both 20 min and 4 min. Remarkably, our proposed xenon lamp treatment process not only promotes charge transfer but also exhibits enhancements of the lattice oxygen in the Zn-O layer. This innovative methodology of xenon treatment yields a notable increase in power conversion efficiency (PCE), achieving 14.55 %, compared to 13.71 % and 12.44 % for the ZnO layers annealed with a hot plate for 20 min and 4 min, respectively. Moreover, devices subjected to the 4-min xenon lamp treatment maintained 85 % (T 85) of their original Power Conversion Efficiency (PCE) after enduring 500 h of one-sun aging measurement. These findings evoke optimism regarding the xenon treatment's potential to streamline the fabrication process, and provide a promising avenue for mitigating interface degradation while enhancing the stability of PSCs. [Display omitted] • High-energy pulses generated by xenon reduce the oxygen vacancies in ZnO film. • Xenon stabilizes the active layer of PM6:Y6, reducing trap-assisted recombination. • Xenon treatment boosts incident light capture, increasing J sc and FF in PSCs devices. • Xenon-treated PSCs maintain T 85 stability, surpassing T 45 from hot plate annealing. [ABSTRACT FROM AUTHOR]

The pervasive use of zinc oxide (ZnO) as an electron transport layer in quantum dot (QD) electroluminescent devices is constrained due to its chemical instability with the QD layer and the formation of interface quenching sites. The effect of fluorine passivation of sol-gel processed ZnO in QD light-emitting devices (QLEDs) is investigated in depth. An examination of the interaction between the ZnO surface and fluorine species revealed that the passivation of oxygen vacancies and the formation of stable hydrogen bonds with hydroxyl groups on ZnO surface have a significant influence on the stability and efficiency of the device. Such exceptional functions of fluorine have been found to effectively capture defects at the interface between ZnO and the emissive layer, therefore mitigating the interface quenching sites. The initial fluorination device demonstrated a significant improvement in external quantum efficiency (EQE) from 5.72 % to 20.07 %, and half of the device lifetime (LT50 at an initial luminance of 1500 cd m−2) was 286 h. Further passivating the remaining active oxygen on the ZnO surface can extend the stability of the device to 542 h with an EQE of 15.2 %, which is among the longest lifetime reported so far for green InP-QLEDs. Our report offers the possibility of utilizing straightforward and highly effective fluorination by spin-coating technique to attain long-lasting InP-QLED devices with remarkable performance. [Display omitted] • Fluorine passivated ZnO was created via the solution spin-coating method by using an NH 4 F solution. • The chemical and thermodynamic stability of ZnO is enhanced through the fluorine alteration on the surface of ZnO. • By optimizing fluorine passivation conditions, a maximum of 2.7 and 11 times improvement in EQE and device stability are achieved respectively. [ABSTRACT FROM AUTHOR]

Carbon-based perovskite solar cells aroused huge attention for their simple, low-cost device fabrication processing and excellent stability. However, the fully low-temperature preparation and flexibility of carbon-based perovskite solar cells remain huge challenges. Here we demonstrate the fabrication of carbon-based perovskite solar cells processed at fully low-temperature, which take thermally evaporated cadmium sulfide as efficient electron transport layer, and obtain an optimal power conversion efficiency of 13.22%. With the decoration of PCBM, the separation of charges at the interface is facilitated and the recombination is hindered, so a higher fill factor is obtained and the efficiency is further improved to 14.28%. Our devices also exhibit good long-term durability and excellent ultraviolet stability. Based on the fully low-temperature preparation process, carbon-based flexible devices are further developed with an optimal efficiency over 9% and considerable mechanical stability, which can serve as the roof-top photovoltaics and power sources for wearable devices. Image 1 • Fully low-temperature processed and flexible carbon-based PSCs with excellent efficiency and stability are demonstrated. • First use of CdS as electron transport layer for carbon-based PSCs. • With the decoration of PCBM, efficiency of the best-performing device is greatly enhanced. [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]

Interfacial engineering is crucial to improve the photovoltaic performance of polymer solar cells (PSCs). In this study, we demonstrate efficient inverted non-fullerene PSCs with ZnO modified by nontoxic glycine (Gly) as the electron transport layer (ETL). With the modification of Gly, work function of the ETL interlayer was decreased from 4.11 eV for ZnO to 4.02 eV for ZnO/Gly, which effectively increased the built-in electric field and hence improved the electron extraction. Furthermore, the surface energy of interlayer was also reduced from 69.1 mJ/m2 for ZnO to 52.5 mJ/m2, which is beneficial for the enrichment of the acceptor at the interface and hence facilities the electron transport and collection at cathode electrode. Therefore, the device based on PM6:IT-4F with ZnO/Gly as ETL exhibited a remarkably enhanced power conversion efficiency (PCE) of 14.0% relative to 12.9% for the control device with ZnO ETL, indicating a ∼9% increase of the PCE with the simple molecular modification of the ETL. Meanwhile, this strategy can also be successfully applied to other non-fullerene and fullerene based inverted PSCs. Our work provides an effective approach to modify ZnO for high performance PSCs. Nontoxic glycine modified ZnO was used as the electron transport layer (ETL), which shows fewer defects, lower work function and lower surface energy, and therefore promote the photovoltaic performance of the inverted non-fullerene polymer solar cells. Image 1 • Nontoxic glycine modified ZnO is used as the electron transport layer in inverted non-fullerene polymer solar cells (PSCs). • The glycine modified ZnO interlayer shows lower work function, fewer defects and lower surface energy. • With the glycine modified ZnO interlayer, higher efficiencies are obtained in the inverted non-fullerene PSCs. [ABSTRACT FROM AUTHOR]

Abstract Metal oxide electron transport layers play a crucial role on the extraction and transportation of charge carriers in organic-inorganic hybrid perovskite solar cells (PSCs). However, generally, fabrication of conductive metal oxide thin films requires high temperature annealing which is not compatible with roll to roll fabrication. It has been observed that a low temperature fabricated pristine metal oxide film exhibited low electrical conductivity, which has still prohibited to achieve high performance of device. Therefore, a low amount of metal doping within the pristine metal oxide films followed by low temperature thermal annealing is an effective approach to improve the electrical properties of the metal oxide thin films, and, thus, leading the higher performance of PSCs. Herein, we have developed a low temperature (180 °C) solution processed Molybdenum (Mo) doped SnO 2 (SnO 2 :Mo) as an efficient electron transport layer (ETL) for the fabrication of planer PSCs. The electrical conductivity of pristine film was significantly enhanced after the incorporation of a small amount of Mo dopant within the neat SnO 2 film, which could facilitate fast transportation of photo-generated charge carriers. Moreover, due to n-type Mo doping, Fermi level of resulting film was slightly shifted upwards, which could diminish charge recombination and, hence, improved the photovoltaic performance. The power conversion efficiency (PCE) for pristine SnO 2 and SnO 2 :Mo based PSCs was found to be 8.47% and 10.52%, respectively, when ETL and perovskite absorber films were processed in ambient conditions with the relative humidity range of 65%–75%. Compared to pristine SnO 2 , SnO 2 :Mo based PSC exhibited higher performance, which was attributed to the enhanced electrical properties of the resulting doped ETL thin film. Our results indicated that low temperature (180 °C) solution processed SnO 2 :Mo is a promising ETL for cost effective roll to roll fabrication of PSC. Graphical abstract Image 1 Highlights • Low temperature (180℃) solution processed Mo doped SnO 2 (SnO 2 :Mo) film as an efficient electron transport layer. • The XPS and SEM with elemental mapping proved the presence of Mo doping in the resulting film. • An optimal concentration of 1.0 mol% SnO 2 :Mo based PSC exhibited highest PCE of 10.52% under ambient conditions. [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]

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]

Abstract We present a solution-processed flexible organic photodiode (f-OPD) with a bulk heterojunction (BHJ) structure based on a blend of poly (3-hexylthiophene-2,5-diyl) and 1-(3-methoxycarbonyl) propyl-1-phenyl[6,6]C 61 (P3HT:PCBM). We used Cs 2 CO 3 -doped polyethyleneimine ethoxylated (d-PEIE) as the electron transport layer (ETL) material, which significantly improved the electron injection properties of the f-OPD. Compared with f-OPDs with conventional ETL materials such as Cs 2 CO 3 , the external quantum efficiency (EQE) of the d-PEIE-based f-OPD was highly improved. Analytical results showed that the d-PEIE reduced the work function of the cathode, thereby facilitating the efficiency of electron injection from the active layer (AL) to the cathode of the f-OPD. In addition, after 10,000 cycles of tensile bending at a bending radius of 5 mm, the normalized I D variation (I D / I D0) in the d-PEIE-based f-OPD remained above 90%, indicating an excellent device bending stability. Finally, f-OPD-based luminescent oxygen (O 2) sensors were successfully fabricated consisting of a photoluminescent O 2 sensing film, a light source, and an f-OPD. The O 2 sensors based on d-PEIE-based f-OPDs showed the highest photocurrent and O 2 sensitivity in relation to the O 2 concentration compared with O 2 sensors based on f-OPDs with conventional ETL materials. Graphical abstract Image 1 Highlights • The solution processed P3HT:PCBM based flexible OPDs (f-OPD) by Cs 2 CO 3 -doped polyethyleneimine ethoxylated (d-PEIE) as the ETL material showed significantly improved optoelectronic and mechanical properties. • The d-PEIE based f-OPD reduced the work function of cathode facilitating the efficient electron injection from the active layer to the cathode of the f-OPDs. • The d-PEIE enhanced the adhesion between the AL and cathode, which improved the mechanical stability of the f-OPDs. [ABSTRACT FROM AUTHOR]

Abstract We introduced phenyl-C61-butyric acid methyl ester (PCBM) as an electron transport layer to improve the performance of metal-oxide-free perovskite solar cells (PSCs) using high-conductivity poly(3,4-ethylenedioxylenethiophene):poly(styrene sulfonate) (PEDOT:PSS) as the cathode. The work function of the PEDOT:PSS was tuned from −5.08 to −4.05 eV by using polyethylenimine, improving the electron collection. Using PCBM improved the electron transport and suppressed the charge recombination of the PSCs. The power-conversion efficiency (PCE) of the rigid PSCs (on glass substrates) was significantly improved from 12.5% to 13.9%, and the open-circuit voltage, short-circuit current density, and fill factor were improved simultaneously. The long-term stability of the PSCs was also improved: the PCE degradation of the PSCs without encapsulation decreased from 18.4% to 13.0% after 114 h. Using a 37-nm PCBM layer, the flexible PSCs on polyethylene naphthalate substrates exhibited a high PCE of 11.4% with good bendability. Our results indicate that using PCBM as an electron transport layer in metal-oxide-free PSCs is a feasible method for the large-scale roll-to-roll production of PSCs. Graphical abstract Image 1 Highlights • High-performance metal-oxide-free PSC produced with PCBM as electron transport layer. • High PCE of 13.9% was achieved for rigid PSCs on a glass substrate. • Long term stability of the PSCs was also improved upon using PCBM. • Flexible PSCs on a PEN substrate exhibited a high PCE of 11.4% with good bendability. [ABSTRACT FROM AUTHOR]

Abstract Organic-inorganic hybrid perovskites have attracted great attentions for photovoltaic applications due to impressive energy conversion efficiency and low cost fabrication. This article reports the effect of photogenerated dipoles in the electron transport layer (ETL) on the photovoltaic actions in perovskite solar cells (PSCs). A nonfullerene material ITIC with optically induced dipoles was doped into PCBM acting as ETL in inverted planar structure PSCs (ITO/PEDOT:PSS/MAPbI 3-x Cl x /ETL/PEI/Ag). The power conversion efficiency (PCE) of PSCs increases from 13.48% to 14.52% with introducing ITIC into ETL. The capacitance measurements indicate that optically induced dipoles can decrease interfacial charge accumulation. Furthermore, impedance spectroscopy suggests the charge recombination as well as ionic migration are reduced with ITIC doped ETL. Steady and transient PL spectra reveal that the electron extraction is more efficient with optically induced dipoles in the ETL. These results provide unique design of ETL in perovskite solar cells. Graphical abstract Image Highlights • ITIC with optically polarizable molecules was introduced into ETL to enhance the photovoltaic performance of PSCs. • The effect of photogenerated dipoles on photovoltaic actions in PSCs were revealed by impedance spectroscopy and PL spectra. • Our results provide a unique method for improving photovoltaic actions in inverted planar structure PSCs. [ABSTRACT FROM AUTHOR]

Abstract Ruddlesden–Popper type two-dimensional (2D) and quasi-2D perovskite-based photovoltaics have been attracting increasing attention due to their high power conversion efficiency (PCE) and long-term stability. In this work, we fabricated inverted 2D perovskite solar cells (PSCs) using a non-fullerene acceptor as electron transport material. Employing a 55-nm thick 3,9-bis(2-methylene-(3-(1,1-dicyanomethylene)-indanone))-5,5,11,11-tetrakis(5-hexylthienyl)-dithieno[2,3-d:2′,3′-d']-s-indaceno[1,2-b:5,6-b']dithiophene (ITIC-Th) as electron transport layer, an average PCE of 8.4% was achieved for the 2D PSCs, which was comparable to that of 2D PSCs based on phenyl-C61-butyric acid methyl ester (PCBM). However, the long-term stability of the 2D PSCs was improved as the degradation of PCE was reduced from 19.8 to 14.6% following a 15-day duration, which can be attributed to the strong hydrophobic property of the ITIC-Th. The best sample based on the 55-nm thick ITIC-Th exhibited a high PCE of 8.9% with a stable power output and negligible hysteresis, indicating the superior electron transport property of ITIC-Th. Our results demonstrate that ITIC-Th is an effective alternative to PCBM to fabricate highly efficient and stable 2D PSCs. Graphical abstract Image 1 Highlights • Non-fullerene acceptor as electron transport layer for 2D PSC fabrication. • High PCE of 8.9% was achieved for fullerene free 2D PSCs. • Long-term stability of the 2D PSCs was enhanced upon using ITIC-Th. • High-performance with stable power output and negligible hysteresis. [ABSTRACT FROM AUTHOR]

We fabricated inverted perovskite solar cells (PSCs) using different organic solvents, including chloroform, chlorobenzene, and 1,2-dichlorobenzene, to prepare the phenyl-C61-butyric acid methyl ester (PCBM) layer. We found that using 1,2-dichlorobenzene resulted in smoother PCBM morphology compared to the chloroform- and chlorobenzene-based solvents; this would be beneficial for improving charge transport between the perovskite and cathode. In accordance with the morphologies, the average power conversion efficiency (PCE) of 1,2-dichlorobenzene-processed PSCs was 17.5%, which was higher than those of chlorobenzene- and chloroform-processed PSCs (16.7% and 11.0%, respectively) The best-performing cell was fabricated using 1,2-dichlorobenzene, showing PCEs of 17.9% and 18.2% in forward and reverse scans, respectively. We found that the conductivity and the PCBM surface roughness showed good linear dependence on the evaporation rate of the solvent, which could be an important factor for identifying new good organic solvents. [ABSTRACT FROM AUTHOR]

The polymer solar cell (PSC) with Ca/Al electrode always suffers from low stability mainly due to the incorporation of oxygen and moisture-sensitive Ca electron-transport interlayer (ETL). To alleviate this problem, air-stable alternatives to Ca ETL are highly desired. Herein, we report two solution-processable, air-stable, effective and inexpensive ETLs based on potassium-neutralized perylene tetracarboxylic derivative (K 4 PTC) and its rGO composite (rGO-K 4 PTC), respectively. These ETL materials were facilely prepared and characterized by means of UV-vis, FL, FTIR, XPS and UPS. Importantly, both ETLs exhibited a low work function (WF) of 4.0 eV, which well matches the LUMO level of fullerene acceptors and allows their use as ETL in PSCs. As a result, the P3HT and PTB7-th-based devices with respective ETL remarkably outperformed those without ETL yielding increases of ∼35% in power conversion efficiencies (PCEs), which indicates good electron-transporting capabilities of K 4 PTC and rGO-K 4 PTC interlayers. The high-performance PSCs with the ETL gave average PCEs of 6.17–6.18% (for PTB7-th:PC 61 BM-based devices) and 7.26% (for PTB7-th:PC 71 BM-based devices), respectively, fairly comparable to those of Ca/Al devices (6.50% and 7.50%). Furthermore, the rGO-K 4 PTC device exhibited stability higher than that of the K 4 PTC device probably due to the fact that the rGO-K 4 PTC layer can provide more efficient protection for the active layer against degradation. Thus, rGO-K 4 PTC layer might be more suitable for real applications as compared to the K 4 PTC layer. [ABSTRACT FROM AUTHOR]

Ink-jet printing is a potentially attractive technique for printing of components for organic electronic devices primarily due to its ability to print patterned layers and reduced ink wastage. However, the mechanism of film formation is quite complex and needs an understanding of various printing parameters on the film growth. In this manuscript, we successfully demonstrate ink-jet printing of smooth zinc oxide (ZnO) thin films with controlled thickness as electron transport layers for inverted organic solar cell devices fabricated on indium tin oxide coated glass substrates. The parameters that strongly affect the formation of a continuous ZnO thin film with controlled thickness are ink concentration and viscosity, substrate surface treatment, drop spacing, substrate temperature during printing and the annealing temperature, affected by a combination of surface energetics, surface tension of the ink and the rate of solvent evaporation. The results suggest that one can achieve a transmittance of >85% for a 45 nm thin ZnO film possessing uniform structure and morphology, fabricated using a drop spacing of 40–50 μm at an ink viscosity of 4.70 cP with substrate held at room temperature. The P3HT:PC 61 BM inverted organic solar cell devices fabricated using printed ZnO films as electron transporting layers exhibit an efficiency of ∼3.4–3.5%, comparable to that shown by the devices fabricated on spin coated ZnO films. Finally, the device with printed P3HT:PC 61 BM active layer on printed ZnO layer showed a device efficiency of ca . 3.2% suggesting that nearly completely printed devices can deliver a comparable performance to the spin coated devices. [ABSTRACT FROM AUTHOR]

We report high-performance inverted red cadmium-free indium phosphide (InP) based QLED devices with Ni-doped ZnO as an electron transport layer (ETL). Using Ni-doping in ZnO, the conductivity and conduction band minimum of ZnO can be modulated, which helps in enhancement of charge balance in the QLED devices. The optimized devices with NiZnO-3% ETL exhibited a maximum current efficiency (CE) and external quantum efficiency (EQE) of 4.9 cd/A and 5.0%. By introducing ZnS interlayer at ETL/QD interface, the exciton quenching is suppressed furthermore. The device with NiZnO-3%/ZnS interlayer revealed a maximum CE and EQE of 10.4 cd/A and 10.6%, which are almost 2.1-fold improved compared to those with reference NiZnO-3% ETL devices. The device also demonstrated a long operational lifetime (LT 70) of 710 h at 1000 cd/m2. The predicted half-lifetime (LT 50) is 164,048 h at 100 cd/m2. Our results indicate that sol-gel Ni-doped ZnO serves a good ETL to attain high efficiency and long lifetime cadmium-free InP-based QLED devices. [Display omitted] • Fabricated inverted red cadmium-free InP-based QLED devices with Ni-doped ZnO as electron transport layer. • Ni doping in ZnO can tune the conductivity and conduction band minimum of ZnO. • Using the ZnS interlayer at ETL/QD interface, the interfacial exciton quenching is suppressed furthermore. • The optimized device showed a maximum EQE of 10.6% with a long operational lifetime of 164,048 h at 100 cd/m2. [ABSTRACT FROM AUTHOR]

Solution processed CH 3 NH 3 PbI x Cl 3– x based planar heterojunction perovskite solar cells with power conversion efficiency (PCE) above 14% are reported. The devices benefit from a phenyl-C 61 -butyric acid methyl ester (PCBM)/ZnO double electron transport layer (ETL) as well as a short air-aging step. The role of the additional ZnO ETL is studied by scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and secondary ions mass spectroscopy (SIMS). Apart from improving the energy level alignment, the ZnO layer blocks the reactions between the metal electrode and perovskite components, increasing the air stability of the device. A crucial step in our processing is a short air-aging step for the device, which significantly increases the device performance by reducing the recombination process. Since the ZnO nanoparticle layer requires no thermal annealing, the maximum temperature to fabricate the device can be kept below 100 °C, making this structure compatible with roll-to-roll processing on plastic films. [ABSTRACT FROM AUTHOR]

In this work, the power conversion efficiency (PCE) of perovskite solar cells (PSCs) was improved by 14.8% (from 11.09% to 12.73%) by using 1,8-diiodooctane (DIO) as a solvent additive during the deposition of phenyl-C61-butyric acid methyl ester (PCBM) layers. The primary reasons for the PCE improvement are the simultaneous increases in the short-circuit current density, fill factor, and open-circuit voltage. The incorporation of DIO improves the morphology of the electron transport layer (PCBM), which plays an important role in charge dissociation, transportation, and collection. Our results indicate that engineering the morphology of the electron transport layer is a simple and effective method for developing high-performance PSCs. [ABSTRACT FROM AUTHOR]

In recent years, the maximum power conversion efficiency (PCE) of perovskite solar cells (PSCs) has exceeded 25%. However, stability, especially under high relative humidity, has become a great obstacle for commercialization of perovskite devices due to its intrinsic defects. Interface modification is an effective method to improve the performance of PSCs for it could validly restrain defects and prevent decomposition of perovskite. In this paper, interface properties have been greatly improved by glycine (GLY) doped SnO 2 electron transport layer (ETL) in planar binary PSCs. SnO 2 -GLY ETL leads to improved band alignment, reduced charge recombination and enhanced electron mobility. XPS and NMR results demonstrate that the ammonia group in GLY combined with perovskite through hydrogen-iodide bonding, which greatly improves the moisture stability of the devices. The best PCE of the perovskite solar cell increased from 19.08% to 21.18%, and GLY modified devices can maintain 88% of its initial PCE after 7 days under 60 ± 5% relative humidity (RH) in ambient condition without any encapsulation. While, thermal stability test results indicating that hydrogen bonding is just a little helpful for improving stability at high temperature. This work indicates that forming hydrogen bonding between perovskite and ETL is an effective way to enhance moisture stability for commercialization of PSCs. [Display omitted] • Interface properties between SnO 2 ETL and PSCs are improved by glycine (GLY), leading to enhanced PCE from 19.11% to 21.18%. • The amino group in GLY is bound to perovskite by hydrogen iodide bond, which greatly improves water stability of the device. • Long-term and thermal stability of the devices have also been improved. [ABSTRACT FROM AUTHOR]

Inverted-structure polymer solar cells (I-PSCs) containing sequentially sprayed electron-transporting layers (ETLs) and photoactive layers were fabricated. Low-temperature sol–gel-derived ZnO thin films were used as the ETLs and films of a poly(3-hexylthiophene) (P3HT)/[6,6]-phenyl-C61-butyric acid methyl ester (PCBM) blend were used as the photoactive layers. Nanoripples-containing ZnO ETLs could be successfully fabricated by controlling the spraying rate of the ZnO precursor solution and the subsequent annealing conditions. The P3HT/PCBM active layers sprayed on the ZnO ETLs were optimized using a unique solvent-assisted post-deposition treatment, namely, the sprayed solvent overlayer (SSO) treatment. The power conversion efficiency (PCE) of the I-PSCs based on the optimized ETLs and active layers was as high as 3.55%, which is comparable to that reported for I-PSCs fabricated using the conventional spin-coating method. The sprayed I-PSCs also exhibited high environmental stability, maintaining ∼80% of their PCE even after 40 days of aging in air under ambient conditions without encapsulation. The I-PSCs based on the P3HT/PCBM photoactive layers optimized using the SSO treatment displayed much higher stability than those based on photoactive layers optimized using a conventional thermal annealing treatment. This result indicated that the SSO treatment is a suitable post-deposition treatment method for improving the morphological stability of P3HT/PCBM active layers. Further, the fabrication technique investigated in this study is a high-throughput low-temperature one and is suitable for fabricating high-stability PSCs. [ABSTRACT FROM AUTHOR]

Highlights: [•] Titanium sol–gel at room temperature. [•] Electron transport layer. [•] Polymer/fullerene bulk heterojunction. [•] Device engineering of organic solar cell. [ABSTRACT FROM AUTHOR]

Abstract: We report on the role of cesium fluoride (CsF) doping on the enhanced electron transport properties of tris-(8-hydroxyquinolin) aluminum (Alq3) for organic light-emitting diodes. The electronic structures of CsF-doped Alq3 layers with various doping concentration are characterized by in situ ultraviolet and X-ray photoelectron spectroscopies, showing an n-type electrical doping effect with Fermi level shift towards unoccupied molecular orbital and the formation of chemistry-induced gap-states. The increase in conductivity and reduction in electron injection barrier in CsF-doped Alq3 layer with optimal doping concentration lead to the enhanced electron injection and transport, which are consistent with the improved electrical characteristics of OLEDs. [Copyright &y& Elsevier]

To realize all-solution processed quantum dots (QDs) light-emitting didoes (QLEDs) with every functional layer processed via wet coating, silver-precursor ink converted cathode is introduced for the first time. One challenge to utilize solution-processed cathode is that the silver-precursor ink reacts with the electron transport layer zinc oxide (ZnO). Another one is that the silver ions permeate through ZnO to quench the QDs' fluorescence. To overcome the challenges, the annealing temperature of ZnO is optimized to 180 °C, while the silver-precursor ink's annealing condition of 180 °C/5 min is selected. As a result, the all-solution processed QLEDs achieve a maximum brightness of 1.32 × 104 cd m−2, a maximum current efficiency of 8.98 cd A−1, and a maximum external quantum efficiency of 6.92% which reaches 61% of the efficiency of QLEDs with evaporated silver cathode. [Display omitted] - Cathode is made by silver-precursor ink to realize all-solution processed QLEDs. - ZnO is annealed at 180 °C to enhance the corrosion resistance. - ZnO can't fully prevents silver ions' permeation from quenching fluorescence. - Silver-precursor ink is converted to silver at high temperature with short time. - Efficiency with solution cathode reach 61% of that with evaporated cathode. [ABSTRACT FROM AUTHOR]

In this work, the extensively used opaque metal cathodes of the conventionally structured OLEDs were replaced with the widely used transparent electrode indium tin oxide (ITO) for solution-processed transparent organic light-emitting diode (T-OLED). A new solution-processable electron transport layer (ETL), aside from facilitating the efficient injection of electrons into the T-OLED, protected the organic emission layer (EML) of the T-OLED against the plasma damage during top ITO cathode sputter deposition. The newly designed solution-processed ETL was the composite of the zinc oxide nanoparticles (ZnO-NPs), and cesium carbonate-doped ethoxylated polyethyleneimine (d-PEIE) with the semi-hydrophilic poly (methyl methacrylate) (PMMA) interlayer coated on the EML insured the good wettability and contact of the hydrophilic ETL with the hydrophobic EML. The solution-processed T-OLED emitted the total maximum luminance of about 2417 cd/m2 (bottom side emission at 1455 cd/m2 and top emission at 962 cd/m2), total maximum current efficiency at 3.12 cd/A (bottom and top emissions at about 1.78 and 1.34 cd/A, respectively), and total maximum power efficiency at 1.64 l m/W (bottom and top emissions at about 0.95 and 0.69 l m/W, respectively) while having a very high optical transmittance of around 85% at 550 nm light wavelength. [Display omitted] • The solution-processed T-OLED with newly designed composite ETL was fabricated. • The electrion injection efficiency and plasma barrier effect of the composite ETL was studied. • The composite ETL had the uniform morphology with even distribution of ZnO in the PEIE matrix. • The T-OLED with composite ETL showed excellent blue light emission. [ABSTRACT FROM AUTHOR]

In this study, sol-gel derived Zn 1-x Mg x O (ZMO) is proposed as an electron transport layer (ETL) for solution-processed quantum-dot light-emitting diodes (QLEDs). It is demonstrated that the increase of Mg content in Zn 1-x Mg x O films from 0% to 20% causes a dramatic suppression of electron current, which is attributed to the lifting of conduction band minimum and reduction of electron mobility. As a result of Mg-doping, the charge carrier balance might be achieved in the QLED with the Zn 0.85 Mg 0.15 O layer resulting in maximum external quantum efficiency of 5.74% and current efficiency of 18 cd A−1, which are over 3-fold higher than in the case of the device with ZnO layer. Improved device performance is further explained by reduced exciton quenching at QDs/ZMO interface, which is confirmed by time-resolved PL experiments. Obtained results indicate that sol-gel derived ZMO is a promising candidate for ETL in quantum-dot based optoelectronic devices. Image 1 • Sol-gel derived ZnMgO might be prepared via low-temperature approach. • Mg-doping reduces the conductivity of ZnMgO films dramatically. • Mg admixture helps to suppress exciton quenching in quantum dots. • ZnMgO serves as an efficient electron transport layer in quantum-dot LEDs. [ABSTRACT FROM AUTHOR]

Although [6,6]-phenyl-C 61 -butyric acid methyl ester (PC 61 BM) has been widely used as electron transport layer (ETL) for inverted perovskite solar cells (PeSCs), it still remains to be improved. Herein, we report that amphoteric imidazole (IZ) and benzimidazole (BIZ) can act as effective and multifunctional dopants for PC 61 BM-based ETL. The resultant MAPbI 3 -xCl 3 -based PeSCs outperform the devices with pristine PC 61 BM ETL with power conversion efficiency (PCE) significantly improved from 14.38% to 15.62/16.47%. Detailed mechanism studies demonstrate that IZ and BIZ-doping cause remarkable reduction of ETL surface roughness and significant increase in electrical conductivity of ETL, both of which facilitate the electron transport from perovskite (PVK) and Ag cathode. More importantly, IZ and BIZ as dopants may passivate both Lewis-acid and Lewis-base type defects on the PVK surface due to their amphoteric nature. DFT computations further reveal that BIZ is a better Lewis-base and Lewis-acid than IZ due to its larger π-conjugation, which thus makes it a superior dopant over IZ. In addition, the PeSCs with PC 61 BM:BIZ based ETL display enhanced device stability by retarding the I− anion migration from PVK to Ag cathode. Image 1 • Imidazole (IZ) and benzimidazole (BIZ) are used as dopants to enhance the performance of PC 61 BM electron transport layer. • IZ and BIZ dopants may passivate both Lewis-acid and Lewis-base type defects due to their amphoteric nature. • The device with PC 61 BM:BIZ display enhanced stability by retarding the I- migration from perovskite to Ag cathode. [ABSTRACT FROM AUTHOR]

High-efficiency organic solar cells (OSCs) based on low-temperature (LT) processed SnO 2 electron transport layer (ETL) are promising for their commercial use. However, high density of traps and large contact barrier for carriers at the interface between LT SnO 2 and the active layer has been reported. To solve the problem, various interface modifying layer materials, such as PFN, has been introduced. Currently, the fabrication process of such interface modifying layer materials is complex and expensive. Herein, a facile strategy involved a polar solvent ethanolamine (EA) is introduced to modify LT SnO 2 surface. By soaking the SnO 2 film into EA solution in 2-Methoxyethanol (2-ME), EA can easily anchor into SnO 2 film surface and forms a continuous monomolecular layer via dehydration reaction. The whole process is green and highly compatible with a roll-to-roll process. Further study suggests that the deep trap centers on SnO 2 surface are substantially reduced and the built-in potential in OSCs is reinforced. Finally, OSCs based on EA-modified SnO 2 demonstrated an enhanced power conversion efficiency from 10.71% to 12.45% which was comparable to those based on ZnO (12.26%) under the same experiment parameters. Our work boosts the development of the inverted OSCs with easy fabrication and compatibility with roll-to-roll process. Image 1 • The EA molecules are bound to the SnO2 film surface through a dehydration reaction. • The EA treatment significantly suppresses the hydroxyl groups related deep-level traps at the SnO2/BHJ interface. • The built-in potential of OSCs is reinforced by using EA treatment at SnO2/BHJ interface. • The EA treatment boosts the efficiency of PBDB-TF:IT-4F based OSCs from 10.71% to 12.45%. [ABSTRACT FROM AUTHOR]

This study demonstrates the effect of electron collection and transportation for TiO 2 electron transport layer (ETL) of the mesoscopic perovskite solar cells (PSCs). The influence of compact TiO 2 layer (c-TiO 2) with various spray cycles, the particle size effect of mesoporous TiO 2 (meso-TiO 2) film and post-treatment of TiO 2 electrode for perovskite solar cells have been studied systematically. We further optimize the meso-TiO 2 thickness to enhance the electron collection and transport efficiency and to reduce the anomalous J-V hysteresis phenomenon of PSCs. After adjusting the fabrication process of TiO 2 ETL, the highest performance of small cell PSC shows the power conversion efficiency (PCE) of 19.39% in the reverse scan and 19.12% in the forward scan, respectively. A sub-module PSC within an active area of 11.7 cm2 exhibits impressive PCE of 16.03% under the illumination of 100 mW/cm2 (AM1.5G). Moreover, it also shows an outstanding PCE of 25.49% under the illumination of 6000 lx of T5 indoor light source. Image 1 • The various sizes of high purity anatase phase TiO 2 nanoparticles (NPs) are synthesized for perovskite solar cells. • The 2L c-TiO 2 and 150 nm meso-TiO 2 film with 22 nm NPs showed the best properties. • Effective charge separation at the perovskite/electron transport layer interface, resulting in the higher FF and V OC. • Smaller TiO 2 particle size has better electron extraction efficiency and results in a less J-V hysteresis behavior. [ABSTRACT FROM AUTHOR]

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]

Zinc oxide (ZnO) nanoparticles (NPs) are extensively adopted material to be used as efficient electron transport layer (ETL) in quantum dot light emitting diodes (QLEDs) due to their suitable properties of high electron mobility, good stability, and easy processability. However, because of the naturally high work function of ZnO NPs, the electrons can be spontaneously transferred at the quantum dot/ZnO interface. In addition, the enormous difference in electron and hole mobility can lead to interfacial exciton quenching and unbalanced charge injection. In this paper, the strategy of replacing the ZnO in QLEDs with Mg and polyvinylpyrrolidone (PVP) inorganic-organic hybrid co-doped ZnO NPs are introduced. The energy band structures of ZnO NPs are tailored by tuning the concentrations of Mg, resulting in a significant suppression of the spontaneous charge transfer at the quantum dot/ETL interface. Furthermore, the surface quenching sites and the electronic mobility of ETL were adjusted via PVP doping. The proposed method significantly enhances the current efficiency and external quantum efficiency to 16.16 cd/A and 15.45%, respectively, an improvement of about 2.5-fold compared to the devices with pure ZnO NPs. Image 1 • ZnO in QLEDs is replaced with Mg and Polyvinylpyrrolidone (PVP) Co-doped ZnO NPs. • ZnO NPs electronic structures are significantly controlled. • The surface quenching sites and the electronic mobility of ZnO NPs were tuned via doping PVP. • The proposed method significantly enhances the external quantum efficiency of QLEDs. [ABSTRACT FROM AUTHOR]

Although chemical bath of TiCl 4 treatment has been used to serve as a compact layer for planar perovskite solar cells (PSCs), uneven TiO 2 particle sizes and chlorine residual would decrease the device performance. In this study, we modify the TiCl 4 treatment process through well-controlled the kinetics grown of TiO 2 nanoparticle, leading to a uniform and ultrathin TiO 2 blocking layer. A dense and pinholeless TiO 2 blocking layer is crucial for high-performance PSCs because of its effective charge extraction and elimination of carrier shunting path. The as-fabricated devices using modified process of TiO 2 blocking layer exhibit the best power conversion efficiency (PCE) of 17.89% with an average PCE of 17.5%. Scanning electron microscopy and cyclic voltammetry analysis of TiO 2 blocking layer reveal that this process improved surface uniformity and the carrier blocking capability. Image 1 • Ultrathin TiO 2 blocking layer was prepared through TiCl 4 solution bath process with repeated treatment under 70 °C. • R4-Ub-TiO 2 -based perovskite solar cell demonstrated a power conversion efficiency of 17.89% in air under AM 1.5G. • Cyclic voltammetry indicated that R4-Ub-TiO 2 had a superior carrier blocking effect and electrochemical stability. [ABSTRACT FROM AUTHOR]