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Electron transport layer (ETL) materials need to have good photoelectric properties and suitable energy levels to match the perovskite layer. Ti 3 CNT x MXene, a typical two dimensional (2D) solid solution, is a potential ETL material due to excellent conductivity and appropriate work function (WF). Herein, Ti 3 CNT x is obtained by optimizing the X-bit inside MXene, and is firstly used as a new ETL for perovskite solar cells (PSCs). Compared with Ti 3 C 2 T x , Ti 3 CNT x possesses lower WF due to the existence of N-H bonds. And the energy level between Ti 3 CNT x and the perovskite layer is more suited to reduce energy loss. Moreover, Ti 3 CNT x interacts with I- ions to passivate defects, enhancing the quality of the perovskite film. As expected, the better power conversion efficiency (PCE) of Ti 3 CNT x -PSC reaches 20.16 %, which is one of the most outstanding PCE among 2D materials used as ETLs. More interestingly, the Ti 3 CNT x -PSC possesses better stability (the PCE retention rate is 70.3 % after 600 h in the air), as a stronger Pb-O bond can reduce Pb0 formation. This work not only reveals the mechanism of interaction between 2D solid solution materials and perovskite, but also explores the vast application prospect of solid solution MXene in PSCs. [Display omitted] • Ti 3 CNT x is firstly used as a new electron transport layer (ETL) for perovskite solar cells (PSCs). • The energy level between Ti 3 CNT x and the perovskite layer is more suited to reduce energy loss. • Ti 3 CNT x interacts with I- ions to passivate defects, enhancing the quality of the perovskite film. • The PCE of Ti 3 CNT x -PSC reaches 20.16 %, which is one of the most outstanding PCE among 2D materials used as ETLs. • More interestingly, the Ti 3 CNT x -PSC possesses better stability. [ABSTRACT FROM AUTHOR]

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]

In emerging organic-inorganic perovskite solar cells (PSCs), the role of efficient electron transport layers (ETLs) is critical for electron transfer and hole blocking. TiO 2 is one of the widely reported ETLs but limits the performance of the devices exhibiting restricted electron mobility and numerous defect states. The process of doping rare earth ions has been an effective approach in improving the electronic and optical properties of TiO 2 for enhanced efficiency of PSCs. The present work studies the effect of praseodymium (Pr3+) doped TiO 2 prepared via sol-gel technique as electron transport layers for lead-free perovskite solar cells. The X-ray diffraction (XRD) and diffuse reflectance spectroscopy (DRS) studies showed that the crystallite size and bandgap of the particles reduced as a function of Pr3+ doping concentration. The X-ray photoelectron spectroscopy (XPS) analysis of the samples inferred that Pr3+ ions majorly remained on the TiO 2 surface. Copper-based (CH 3 NH 2) 2 CuBr 4 perovskites were synthesized by solution method as an active layer for the solar cells. XRD, FTIR (Fourier Transform Infrared Spectroscopy) and XPS analysis confirmed the formation of 2D-perovskite phase of the samples. The scanning electron microscopy (SEM) analysis of the perovskites revealed well crystalline orthorhombic structures. Current-voltage measurements were carried out to study better passivation properties with rare-earth doping of the ETLs and was found to be most enhanced for 0.07 Pr3+ concentration. Electro-chemical Impedance Spectroscopy (EIS) studies of the solar cells showed a reduced interface recombination and enhance charge transfer properties as a function of rare-earth dopant concentration. Further, the fabricated perovskite solar cells showcased better performance with xPr3+:TiO 2 ETLs and the maximum efficiency of ∼1.25 % was obtained for TiO 2 : 0.07 Pr3+. [ABSTRACT FROM AUTHOR]

As a new and efficient solar cell, perovskite solar cell has attracted wide attention due to its excellent performance. The electron transport layer in perovskite solar cells has a significant impact on device performance. SnO 2 films that can be prepared by solution method have become the first choice for electron transport layer due to their simple process and excellent performance. However, the defects in SnO 2 thin films and non-radiative recombination sites at the SnO 2 /Perovskite interface will lead to potential losses in the performance of photovoltaic devices. Therefore, in order to improve the interface loss and interface characteristics and prepare more efficient perovskite solar cells. In this work, a functional polymer, polyvinyl alcohol (PVA), is introduced to regulate the arrangement of SnO 2 nanocrystals. The SnO 2 -PVA composite electron transport layer not only improves carrier transport, but also further affects the growth of perovskite films. PVA inhibits the agglomeration of tin dioxide particles by adding it to the aqueous solution of tin dioxide. Meanwhile, the oxygen vacancy defects in the SnO 2 layer have also improved. Correspondingly, SnO 2 -PVA-based PSCs can be obtained a maximum efficiency of 23.73 %. Attributed to the strengthened interface binding and the improved perovskite crystallization process, the devices obtain good long-term stability, retaining 90 % of their initial performance after 1000 h operation at their maximum power point under 1 sun illumination. [Display omitted] • A functional polymers PVA is used in p-i-n PSC, and gain a PCE of 23.73 %. • The electronic extraction efficiency and conductivity of SnO 2 are enhanced by PVA. • SnO 2 -PVA-based device presented outstanding stability under 1 sun illumination for over 1000 h. [ABSTRACT FROM AUTHOR]

• Highly uniform electrodeposited mesoporous TiO 2 as an electron transporting layer for perovskite solar cells. • Impact of high temperature to mesoporous TiO 2 porosity. • Superiority of electrodeposition to traditional spin-coating mesoporous film toward large-area perovskite solar cells. In this study, we present the utilization of electrodeposited TiO 2 mesoporous film (ED-MS-TiO 2) as the electron transport layer (ETL) for perovskite solar cells, especially marking the first report of its application in perovskite solar modules. In the first part of this paper, we refine the electrodeposition process to enhance the porosity of the ED-MS-TiO 2 thin film by elevating the ED temperature from room temperature to a mild 60 °C. Notably, the ED-MS-TiO 2 ETL fabricated at 60 °C demonstrates comparable charge extraction capability and conversion efficiency to the benchmark ETL produced via the widely adopted spin-coating technique, achieving a remarkable 20.5 %. Furthermore, we demonstrate the immense superiority of the ED process in achieving uniformity in the preparation of large-area ETLs. Our current findings reveal that ED-MS-TiO 2 exhibits exceptional uniformity control, with a thickness distribution of 122.69 ± 8.39 nm on a 100 cm² substrate, while its spin-coated counterpart exhibits poor thickness control, measuring 135.72 ± 50.72 nm. Moreover, perovskite solar modules (5 cm × 5 cm) employing the optimized ED-MS-TiO 2 ETL attain an impressive efficiency of 15.63 %, surpassing counterparts utilizing spin-coated TiO 2 ETLs, which achieve only 9.70 %. [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]

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]

Perovskite solar cells (PSCs) play a pivotal role in advancing renewable energy to achieve United Nation's Sustainable Development Goal 7 (SDG 7), which aims to ensure universal access to affordable, sustainable, reliable and modern energy services. Aiming to enhance the performance of PSCs by replacing the typically used electron transport layers (ETLs: TiO 2 , SnO 2 , ZnO etc.), we theoretically investigated the viability of tungsten oxide (WO X) as a promising ETL for PSCs. Moreover, the effect of altering the energy levels of WO X on cell performance has also been analyzed through simulation. Initially, 12 (twelve) PSC structures having the combination of different perovskite (PSK: CsPbBr 3 , CsPbI 3 , FAPbBr 3 , FAPbI 3) absorber layers with different organic hole transport layers (HTLs: Spiro-OMeTAD, P3HT, PEDOT:PSS) and a fixed ETL of WO X were optimized numerically for comparing their performance. As CsPbBr 3 -based PSCs showed the best performance, further simulations were performed by varying some WO X /CsPbBr 3 interface properties such as interface defect density, conduction band offset (CBO) between WO X and CsPbBr 3 , energy bandgap (E g) of WO X etc. Finally, the best-performed PSCs were found for the E g = 3.5 eV of WO X and the CBO of - 0.5 eV confirming the conduction band minimum (CBM) of WO X is lower than that of CsPbBr 3 by 0.5 eV. A properly chosen WO X layer enhanced the efficiency of CsPbBr 3 -based PSCs up to 14.65 %, 14.52 % and 16.09 %, aproaching the Shockley-Queisser (S-Q) limit (16.37% for CsPbBr 3 -based solar cell) from the initial values of 11.39 %, 11.27 %, and 12.49 %, respectively. This study ensures WO X is a promising ETL for which a proper PSC structure having a suitable PSK and an HTL can improve cell performance. Moreover, the importance of modifying energy levels of ETL material in enhancing the performance of PSCs is explored. As a result, this study opens a path for the researchers to develop WO X having suitable CBM and E g , so that it can be well-suited with a properly matched PSK material resulting in enhanced cell performance. • PSCs consisting of Cs and FA-based different perovskites and WO X as ETL are studied theoretically. • CsPbBr 3 -based PSCs having WO X as ETL exhibit the best performances. • WO X /CsPbBr 3 interface properties are varied to study their effect on cell performances. • The position of the conduction band minimum and energy band gap of WO X are optimized. • The identified optimum value conduction band offset at the WO X /CsPbBr 3 interface is −0.5 eV. [ABSTRACT FROM AUTHOR]

• Novel Sr-doped BaTiO 3 ETL enhances perovskite solar cell performance beyond traditional TiO 2 layers. • BST-incorporated PSCs achieve 16.32% efficiency, with potential to reach 28.65% in optimized devices. • FDTD simulations reveal BST's superior optical and electrical properties compared to BTO-based cells. • Findings advance interfacial engineering in PSCs, promising significant improvements in photovoltaic technology. This work investigates the potential of BaTiO 3 (BTO) and Sr-doped BaTiO 3 (BST) as electron transport layers (ETL) in perovskite solar cells (PSCs) through Finite-Difference Time-Domain (FDTD) simulations. A comprehensive analysis was conducted to optimize the thickness of each layer in the PSC structure, with the aim of enhancing the photovoltaic performance and stability. Results indicate that BST-based PSCs exhibit superior optical and electronic properties compared to BTO-based PSCs, achieving higher ultimate efficiency (28.65 %) and power conversion efficiency (16.32 %). This improvement is attributed to better band alignment and higher electron mobility in BST, which enhances charge separation and reduces recombination losses. Optical analysis reveals that BST-based PSCs have a consistently higher spectral response across all wavelengths, indicating more effective light absorption and conversion into electrical current. The external quantum efficiency (EQE) of BST-based PSCs is consistently higher, resulting in an increase in Jsc of 16.87 mA/cm2 compared to 15.96 mA/cm2 for BTO-based cells. These findings highlight the potential of BST as a superior ETL material for high-performance PSCs, offering light management and charge-transport properties improved compared to those of conventional BTO-based ETLs. [ABSTRACT FROM AUTHOR]

In recent years, the research on silicon heterojunction (HJT) solar cells based on dopant-free contacts has experienced rapid development. Zn(O,S) is a low work function n-type semiconductor compound with tunable band gap that can be used as the electron transport layer (ETL) in HJT solar cells. In our work, we choose Zn(O,S) as ETL and deposit it via the low-cost chemical bath deposition (CBD) method. Uniform and fast growth of Zn(O,S) films can be obtained by regulating the concentration of the complexing agent and the ratio of reactants to reduce the generation of impurities. To further achieve band matching with c-Si, the Zn(O,S) films are processed with air-annealing to modify the elemental ratios. The air-annealing lowers the interfacial electron transport barrier, which promotes charge separation and transport, thus reducing carrier recombination at the interface. Finally, the PCE of HJT solar cell based on CBD-Zn(O,S) ETL is close to 15 %, providing a new potential route for the development of low-cost HJT solar cells. [Display omitted] • The first attempt to use chemical bath deposition of single-sided Zn(O,S) films as electron transport layer in crystalline silicon heterojunction solar cells. • High-quality films can be rapidly generated by controlling the concentration of reactants to reduce the interfacial contact resistance. • The air-annealing treatment reduces the film impurities while further minimizing the conduction band offset with c-Si. [ABSTRACT FROM AUTHOR]

In this paper, we report the amorphous Ge NPs film which is fabricated at room-temperature by PECVD method. The uniform, compact and smooth film is formed by orderly packing of the Ge NPs in the longitudinal direction, resulting in the formation of columnar structures in the Ge NPs film. The electrical, optical properties and energy levels of the Ge NPs film meet the requirements of the OSCs for ETL, and the PTB7:PC 70 BM OSCs with the Ge NPs ETL shows the PCE of 7.38%. [Display omitted] • The amorphous Ge NPs film is fabricated by using the PECVD method at room temperature. • The compact and orderly packing of the NPs in the longitudinal direction leads to the formation of columnar structures in the Ge NPs film. • The electrical, optical properties and energy levels of the Ge NPs film meet the requirements of the OSCs for ETL. • The PTB7:PC 70 BM OSCs with the Ge NPs ETL shows the PCE of 7.38%. The performances of the organic solar cells (OSCs) largely depends on the selection and preparation of the electron transport layer (ETL). In this paper, the uniform and compact Ge nanoparticles (NPs) film was fabricated by using the plasma enhanced chemical vapor deposition (PECVD) method at room temperature. The Ge NPs film is formed by close packing of amorphous Ge particles with an average diameter of 6.05 nm, and the film shows a fairly smooth surface with a root-mean-square (RMS) roughness of 0.6419 nm. The results shows that Ge NPs film exhibits n-type characteristics, and the longitudinal conductivity of the film is 1.90 × 10−5 S/cm, which is better than that of the ZnO NPs film. The excellent longitudinal charge transport characteristics is attributed to the existence of the columnar structures in the Ge NPs. In addition, the Ge NPs film shows a visible light transmittance comparable to that of the ZnO NPs film. More importantly, the energy levels of the Ge NPs film meets the requirements of the PTB7:PC 70 BM OSCs for the ETL, and the devices with the Ge NPs ETL shows the power conversion efficiency (PCE) of 7.38%. The characteristic of room temperature preparation make the Ge NPs ETL may become a reliable choice for the flexible devices in the near future. [ABSTRACT FROM AUTHOR]

• The photovoltaic characteristics of ZnO layer effects on the PSCs is studied. • The morphology of layer ZnO layer thickness was investigated by SEM and AFM. • ZnO layer thickness increased, the (ECE) is also increased to 15.22%. • The high ECE was due to the enhanced electrical conductivity ZnO layer. • The surface valley spacing in the ZnO layer may affect the grain size and thickness. The energy loss in perovskite solar cells (PSCs) is a key factor that limits the potential scope of photovoltaic performance. Herein, we introduce a double electron transport layer (DETL) that consists of SnO 2 /ZnO and use it to prepare methylammonium lead triiodide (MAPbI 3)-based planar heterojunction PSCs for mitigating the energy loss. We investigated the photovoltaic properties of DETL PSCs concerning the varying thickness of the ZnO layer. The thickness of DETL in each device was measured using an electron probe microanalyzer. UV–vis-NIR spectroscopic as well as different microscopic techniques including SEM and AFM were employed for an in-depth investigation of the prepared devices. The best PSC device in our study showed a comparatively improved energy conversion efficiency (ECE) of 15.22% with an optimized thickness of ZnO up to 210 nm. [ABSTRACT FROM AUTHOR]

[Display omitted] • Green synthesized ZnO nanoparticles as ETL in perovskite solar cells. • ZnO, bilayered and composite ETLs involving ZnO and SnO 2 highly affect the charge transport mechanism of the device. • Improved J-V behaviour and interesting capacitive responses support better charge transport for composite ETL. Utilizing green-synthesized ZnO nanoparticles as an electron transport layer (ETL) is a key strategy in perovskite solar cell applications, leveraging their high electron mobility, conductivity, stability against photo-corrosion, and cost-effectiveness. In this study, these environmentally synthesized nanoparticles, combined with SnO 2 , formed a composite solution-processed ETL achieving an impressive 18.09 % device efficiency, with 1.06 V open circuit voltage, 71.71 % fill factor, and 23.80 mA/cm2 short circuit current density. These values underscore the composite material's potential for device applications. Additionally, capacitance measurements investigated ETL and absorber layer interfaces, yielding crucial insights into their behaviour under varying voltage, frequency, and illumination conditions. The study highlights the ZnO-NP and SnO 2 composite's efficacy as a superior ETL in PSCs, emphasizing the environmental sustainability implications of employing green-synthesized materials in solar energy technologies. [ABSTRACT FROM AUTHOR]

[Display omitted] • Atomic-level precision SnO 2 thin films were grown by a pulsed laser deposition (ALD) method. • The ALD conditions were fine-tuned to examine their effects on film properties. • The carrier concentration and Fermi level tended to increase with increasing the growth temperature, while the surface roughness and oxygen content showed the reverse trend. • PSCs with SnO 2 ETLs grown at various ALD conditions were fabricated and tested. • A PSC with a 15 nm-thick SnO 2 ETL grown at 200 °C showed the best cell performance. The electron transport layer (ETL) of a perovskite solar cell (PSC) plays a pivotal role in determining cell performance. In this work, an atomic layer deposition (ALD) technique was employed to grow high-quality SnO 2 thin films, and those ALD-grown SnO 2 films were used as ETLs of PSCs. The properties of films and the performance of PSCs were closely examined depending on the SnO 2 growth conditions. The SnO 2 films grown at higher temperatures showed a very small surface roughness (≤0.6 nm) though grown faster. The relative oxygen content of the film was inclined to decrease with increasing the growth temperature. Consequently, the carrier concentration and the Fermi level of the film became higher at elevated temperatures. PSCs with ALD-grown SnO 2 ETLs also revealed a clear correlation between cell performance and the film growth temperature. The results of this work may offer practical guidelines for enhancing the performace of a PSC that employs a metal oxide as an ETL. [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]

Abstract Developing novel low-cost and efficient electron transport layer (ETL) materials for high-efficiency planar heterojunction perovskite solar cells (PSCs) still remains challenges. Herein, we report a low-temperature colloid-synthesized and solution-deposited strontium stannate SrSnO 3 (SSO) perovskite oxide nanoparticle can be an effective alternative ETL. More importantly, the introduction of yttrium dopant results in a significant improvement in the optoelectronic properties of yttrium-doped SrSnO 3 (YSSO), exhibiting higher electron conductivity and faster electron transfer, as well as better band alignment at ETL/perovskite interface compare to undoped SSO, which is also supported by theory calculation. Consequently, these factors boost all photovoltaic performance parameters, leading to an improvement in the efficiency of planar PSCs. The resulting YSSO-based PSCs exhibit an average efficiency of 17.8% and a maximum power conversion efficiency of 19.0% with the significant reduction of J–V hysteresis, and those devices show high long-term stability as well. Our findings provide the full potential of the perovskite oxide toward future photovoltaic applications, especially for cost-efficient planar PSCs. Graphical abstract fx1 Highlights • First colloid-synthesis and solution-deposition of Y-SrSnO 3 perovskite oxide. • Y-SrSnO 3 is used as an effective ETL for planar perovskite solar cells. • 19.0% power conversion efficiency with negligible hysteresis and high stability. [ABSTRACT FROM AUTHOR]

Abstract In this study, an ideal planar perovskite solar cell (PSC) has been proposed and simulated by using Tungsten Disulfide (WS 2) as an electron transport layer (ETL). Effects of various amphoteric defect states of PSC based on CH 3 NH 3 PbI 3−x X x absorber layer and the interface properties of both ETL and hole transport layer (HTL) are quantitatively analysed by SCAPS-1D numerical simulator. Results show that the device performance is highly influenced by amphoteric defects in the absorber layer rather than the interface defects layer (IDL). It is also revealed that the quantitative tolerable range in CH 3 NH 3 PbI 3−x X x and IDLs are less than 1015 cm−3 and 1016 cm−3, respectively. The PSC exhibits better performance in the range of 10 °C–40 °C and degrades gradually at higher temperature. With the proposed structure, the simulation finds the highest power conversion efficiency (PCE) of PSC to be 25.70% (Voc = 1.056 V, Jsc = 25.483 mA/cm2, and FF = 88.54%). [ABSTRACT FROM AUTHOR]

[6, 6]-phenyl C 61 butyric acid methyl ester (PC 61 BM) is a common fullerene derivative widely employed as an electron transport layer in inverted perovskite solar cells. However, major challenges such as interfacial recombination, current leakage and low mobility results in poor photovoltaic performance and stability for PC 61 BM-based devices. To overcome these issues, we demonstrated, for the first time, doping of the PC 61 BM with fullerene C 60 to tailor the properties of the PC 61 BM. This doping approach helped to realize superior power conversion efficiency of perovskite solar cell with 17.46% versus pristine device with 14.20%. The C 60 doped PC 61 BM reinforced the surface morphology of the PC 61 BM layer with reduced roughness and better coverage, up-shift of Fermi Level, higher electrical conductivity, higher maximum charge carrier generation rate, and higher charge collection probability. All these improvements contributed to reduced charge leakage at the interface, reduced charge recombination and promoted efficient charge transfer, transport, and collection. Furthermore, the enhanced hydrophobicity of the C 60 doped PC 61 BM enabled superior ambient device stability compared to the pristine device. This work facilitates a simple and effective route to tailor perovskite solar cell performance towards higher efficiency and better stability. [Display omitted] • Doping C 60 into PC 61 BM ETL is a promising route to enhance PSCs performance. • Doping C 60 into PC 61 BM improved the film surface morphology of the PC 61 BM ETL. • Charge leakage at the interface, and charge recombination were decreased. • Electrical conductivity, charge generation, and charge collection were increased. • PC 61 BM:C 60 ETL increased efficiency of PSC by 23% and exhibited superior stability. [ABSTRACT FROM AUTHOR]

For planar perovskite solar cells (PSCs) to have satisfactory performance and acceptable stability, an ETL (electron transport layer) is needed that provides a high level of efficiency. It should be noted that when considering the implementation of n-type metal oxide materials, the ZnO (zinc oxide) can be a great choice for an ETL because it provides a relatively high level of mobility. The current study proposes a new design involving a reduced graphene oxide (rGO) sheet/Ag-doped ZnO bilayer to be utilized as ETL in planar PSCs. Extensive experimental and computational analyses including nano-micro structural, optical and electrical properties are carried out in order to compare the performance and governing mechanisms of rGO/Ag-doped bilayer-based planar PSC to ordinary un-doped ZnO. The results from the performed experiments show that using the rGO sheet as the buffer layer and Ag-doped ZnO significantly increase the power conversion efficiency (PCE) by more than 30% compared to un-doped ZnO ETL in planar PSCs. These improvements in the performance of PSCs can be explained based on fine tuning the energy levels of ZnO/perovskite, since this increases the charge-carrier-extraction from the perovskite layer. Moreover, the results of the study confirm the using the rGO/Ag-doped ZnO bilayer ETL as a new methodology for the creation of stable planar PSCs with low charge recombination rate and high performance. [ABSTRACT FROM AUTHOR]

Organic solar cells (OSCs) with an inverted structure have the potential to exhibit both high efficiency and stability, in which the electron transport layer (ETL) plays a crucial role. In this study, we have developed an efficient ETL for inverted structure OSCs by modifying commercially available SnO 2 nanoparticles with a simple molecule 2-(3-(dimethylamino)propyl)− 1,3-dioxo-2,3-dihydro-1 H-benzo[de]isoquinoline-6,7-dicarboxylic acid (NMA). The surface modification effectively eliminates the light soaking issue observed in devices with bare SnO 2. Furthermore, it significantly enhances the efficiency and stability of the photovoltaic devices. With the hybrid ETL, the device based on PM6:L8-BO achieves an outstanding power conversion efficiency (PCE) of 18.33 %. Notably, the champion device exhibits excellent shelf, thermal and photo stabilities. It maintained 99.7 % and 87.1 % of its original efficiency under storage in N 2 and thermal stress at 65 ℃ for 1000 h, respectively. Under continuous 1-sun illumination with maximum power point tracking for 800 h, the device retained 86.6 % of its initial efficiency. Additionally, the hybrid ETL shows good generality on other typical active layer systems based-OSCs. This work presents an effective hybrid ETL approach for the development of high-performance OSCs. [Display omitted] • An efficient hybrid ETL for inverted structure OSCs is reported by modifying SnO 2 nanoparticles with a molecule named NMA. • The surface modification effectively eliminates the light soaking issue observed in devices with bare SnO 2. • The OSC based on the hybrid ETL achieves an outstanding efficiency of 18.33 % and demonstrates excellent stabilities. [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]

[Display omitted] • The introduction of potassium bitartrate (KBT) into the TiO 2 film improves TiO 2 surface smoothness and charge transport, reducing recombination centers in PSCs. • KBT in TiO 2 ETLs enhances PSC morphology, reduces interface defects, and improves energy alignment, leading to higher efficiency and stability. • PSCs with KBT show a significant efficiency increase to 23.35 % and maintain over 80 % efficiency after 800 h. The performance of perovskite solar cells (PSCs) has rapidly improved, largely due to advancements in mitigating inherent defects and enhancing interface carrier transport properties. Herein, we provide a facile method to improve the morphology of TiO 2 ETLs, suppress defects at interface, and tailor energy level alignment to enhance carrier separation and extraction efficiency by introducing potassium bitartrate (KBT) into the TiO 2 electron transport layers (ETLs), achieving high-efficiency and stable PSCs. KBT molecules can enhance the surface smoothness of TiO 2 ETLs, resulting in denser and more uniform perovskite films. In addition, the carboxyl groups, hydroxyl groups, and potassium cations containing in KBT improve charge transport efficiency at TiO 2 /perovskite interface by reducing non-radiative recombination centers in TiO 2 and perovskite bottom as well as improving energy level matching. As a result, the target PSC exhibits an obvious improvement in performance with a champion efficiency of 23.35 %, which is greatly improved relative to the control (21.66 %). The long-term operational stability is also remarkably enhanced, after 800 h MPPT, PSCs with KBT remain over 80 % of its initial efficiency. PSCs with KBT-doped ETLs exhibit increased efficiency and stability, highlighting potential of KBT as an interface engineering tool for enhancing PSCs performance. [ABSTRACT FROM AUTHOR]

TiO 2 is one of the most widely explored materials as an electron transport layer (ETL) in dye sensitized solar cells (DSSCs) due to its excellent physical and chemical properties. However, recombination at the device's interface slackens the charge carrier movement, adversely affecting their device performance. Rapid extraction of photogenerated charge carriers plays a vital role in developing high efficiency DSSCs. The conduction band alignment of TiO 2 ETL and N719 dye light absorber plays a crucial role in charge carrier dynamics of DSSCs. Herein, the band structure of TiO 2 ETL is finely tuned by the incorporation of cesium bromide (CsBr). At the optimal concentration (0.4 Wt. %), DSSCs achieved the best power conversion efficiency (PCE) of 9.28 % compared to 7.61 % for pristine TiO 2. The modified TiO 2 –CsBr ETL induced a negative shift in flat band potential (V f b) from −0.46 to −0.50 V, which improved the open circuit voltage (V OC), its work function (ɸ) from −4.71 to −3.75 eV and increased conduction band minimum (CBM) from −3.58 to −2.42 eV. CsBr incorporation increased electron density in TiO 2 matrix, indicating the suppression of trap state and significantly improved the overall photovoltaic performance of DSSCs. • DSSC fabricated with TiO 2 –CsBr (0.4 Wt.%) electron transport layer achieved the best power conversion efficiency of 9.28 %. • The modified TiO 2 –CsBr induced a faster electron transport and shifting flat band potential (V f b) from −0.46 to −0.50V. • After modification the work function (ɸ) of TiO 2 reduced from −4.71 to −3.75eV. [ABSTRACT FROM AUTHOR]

Abstract Perovskite solar cells (PSCs) are currently exhibiting reproducible high efficiency; the manufacturing of low cost, scalable electron transport layers (ETLs) is becoming increasingly important. However, this remains a challenge for electron transport layers that exhibit excellent optical/electrical properties while being a thin film of simple morphology. Here we demonstrate the PSC of a 2D photonic crystal nanodisk (ND) array ETL that is compact, but greatly enhances light harvesting. The ND array is fabricated by nanosphere lithography using a monolayer of self-assembled polymer spheres as a physical mask. We fabricate ND arrays of various lattice constants simply by controlling the size of the polymer spheres. Optimal ND arrays exhibit strong forward scattering and optical confinement effects, greatly improving light harvesting in the perovskite layer. We also observe that the ND array improves charge transport by reducing contact resistance with the perovskite layer. ND array ETL PSCs reach 19% maximum power conversion efficiency, with low photocurrent-voltage hysteresis and stable photocurrent output. Graphical abstract We demonstrate a perovskite solar cell with a 2D photonic crystal as an electron transport layer and achieve a power conversion efficiency of up to 19% by the effect of improving light harvesting by photonic crystals. fx1 Highlights • We introduce TiO 2 electron-transport layer with a thin-film 2D photonic crystal structure. • We present the surface relief pattern electron-transport layer of a TiO 2 nanodisk array fabricated using nanosphere lithography. • 2D nanodisk perovskite solar cells achieve a maximum power conversion efficiency of 18.7%. • The nanodisk perovskite solar cells also showed low hysteresis in power conversion efficiency and stable efficiency output. [ABSTRACT FROM AUTHOR]

This work examines the adoption of radio frequency (RF) sputtering at power ranging from 100 to 300 W to deposit nanostructured titanium dioxide (TiO 2) thin films on indium tin oxide (ITO)-coated polyethylene terephthalate (PET) flexible substrate (ITO/PET) at room temperature. At higher RF power, X-ray diffraction (XRD) results exhibited evolution from amorphous into crystalline anatase with preferred (101) orientation and the films revealed spherical-like nanostructures with increasing grain size from 15.71 to 21.57 nm. Films transparency decreased from 79% to 70%. Estimated energy gap decreased from 3.57 to 3.36 eV, while refractive index increased from 2.19 to 2.25, denoting a red shift in the films. The thin film deposited at 300 W exhibited high conductivity and mobility of 19.65 × 10−5 Ω−1 cm−1 and 0.30 cm2/Vs, respectively. The film demonstrated its capability as an electron transport layer for flexible perovskite solar cells. [ABSTRACT FROM AUTHOR]

• TiO 2 electron transport layer deposited by ALD at about 150 °C. • SnO 2 /PCBM double modifier at TiO 2 /perovskite interface. • Low-temperature processed perovskite solar cells with a PCE of 19.45%. • Enhanced performance compared to devices with solution processed TiO 2. Perovskite solar cells (PSCs) have attracted increasing attentions for their outstanding efficiency and simple fabrication process. However, the commonly used typical titanium dioxide (TiO 2) electron transport layer (ETL) requires a high-temperature treatment to crystallize. In this work, the low-temperature (150 °C) atomic layer deposition (ALD) processed TiO 2 ETL, and the SnO 2 /PCBM double interfacial modifier have been adopted to fabricate the high performance PSCs of ITO/ALD-TiO 2 /SnO 2 /PC 61 BM/MA 0.7 FA 0.3 PbI (3-x) Cl (x) /Spiro-OMeTAD/Ag. The measurement results show that the PSCs with ALD-TiO 2 ETL obtain the higher champion PCE of 19.45% than that of PSC with solution-TiO 2 ETLs (PCE = 18.64%), along with the obviously enhanced FF and V OC , as well as the better light stability and repeatability. And the transient photocurrent and photovoltage results demonstrate that the performance improvement origins from the enhanced charge transport and suppressed charge recombination. Therefore, the low-temperature ALD-TiO 2 ETL with suitable modification is a promising strategy to fabricate efficient PSCs and flexible devices. [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]

Graphical abstract Highlights • The charge carrier mobility can be effectively improved by doping Ag into TiO 2 electron transport layer. • Ag-doped TiO 2 electron transport layer can reduce the J-V hysteresis. • The PCE of perovskite solar cell based on 1.00 mol% Ag-doped TiO 2 electron transport layer reached to 17.7%. Abstract Organic-inorganic hybrid perovskite solar cells (PSCs), a superstar of photovoltaic devices, have attracted people's attention owing to their adjustable energy band gap value, extremely high absorption coefficient, long charge carrier diffusion length, and dramatically high power conversion efficiency. In recent years, researchers have tried hard to explore new strategies in order to obtain better optical characteristics. Metal ion-doped electron transport layer (ETL) is a convenient way to improve the optical properties of PSCs. By this method, the conduction band and valence band position can be changed. This can lead to the carriers can effectively transport, and the charge recombination between ETL and absorber layer be reduced. In our study, we have enhanced the photovoltaic performance and the hysteresis behavior of the device by using various concentrations of mesoscopic Ag-doped TiO 2 (meso-Ag:TiO 2) as the ETL. We also systematically discussed the surface morphology, the charge carrier dynamic, the electron mobility, and the electrical conductivity for our devices. Finally, by optimizing the parameters of PSCs and the energy band alignment between perovskite absorber layer and ETL, the power conversion efficiency (PCE) of the champion device with 1.00 mol% meso-Ag:TiO 2 ETL reached as high as 17.7%. [ABSTRACT FROM AUTHOR]

Incorporation of gold nanoparticles in the ZnO electron transport (ETL) layer improves the power conversion efficiency (PCE) of organic solar cells via the plasmonic effects causing enhancement in the light absorption of the active layer as well as improved interface between the ETL and the active layer. The best device showed a PCE of 11.8%, 24% higher than that of control device and is among the best observed values for widely explored bulk heterojunction solar cells based on PTB7-Th:PC 71 BM. • Demonstration of 24% improvement in efficiency over control organic solar cells on addition of Au NPs to ZnO ETL. The resulting efficiency is 11.8% which is one of the highest obtained in literature for PTB7-Th:PC 71 BM system. • Exhibited the effect of Au NPs concentration on device performance and explored the enhancement mechanisms in detail for the optimal concentration. • Investigated the interfacial properties of the resulting ETL with AU NPs which unraveled the role of Au NPs in pacifying defects on ZnO surface. In bulk hetero-junction organic solar cells (BHJOSCs), light absorption can be improved by employing techniques such as plasmonic effects which can lead to improved device efficiencies. In this manuscript, we demonstrate highly efficient devices obtained upon incorporation of gold nanoparticles (Au NPs) of size 10–20 nm at various concentrations into solution processed ZnO (zinc oxide) electron transport layers (ETLs). The inverted OSC devices of configuration ITO/ZnO:Au NPs/PTB7-Th:PC 71 BM/MoO 3 /Ag show the highest power conversion efficiency (PCE) for an optimum concentration of Au NPs (0.05 wt%) in ZnO ETL layer driven by plasmonic effects leading to improved light absorption and improved interface between the active layer and the ETL leading to improved carrier collection. The effects together cause enhancement in the short circuit current density (J sc) and fill factor (FF) leading to a maximum PCE of 11.8% with an open circuit voltage (V oc), short circuit current density (J sc), and fill factor (FF) of 0.80 V, 21.75 mAcm−2, and ~68%, respectively. This PCE is 24% higher than the control device (ZnO ETL without Au NPs) and is among the best observed values for widely explored bulk hetero-junction (BHJ) solar cells based on PTB7-Th:PC 71 BM. [ABSTRACT FROM AUTHOR]

• A facile sputter method for a double layer oxide electron transport layer (DETL). • The efficiency of the device-DETL is 35% higher than the reference device. • DETL could balance the photo-generated charge separation and recombination. • A new idea about recombination suppress: modulate the ratio of fast/slow pathways. PbS colloidal quantum dot solar cells (CQDSCs) employ ZnO electron transport layer have achieved high efficiency. However, there is nearly no efficient and batch production method to balance the charge separation and recombination within the device, which is one of the most obviously barrier to a satisfactory conversion efficiency. Here, a n+-n double-layered ZnO electron transport layer (DETL) is prepared by a facile one-step magnetron sputtering under different Ar pressure, and employed in heterojunction PbS colloidal quantum dot solar cells (CQDSCs) for the purpose of increasing charge separation at heterojunction interface via energy-band alignment modulation. The ZnO DETL, composed of a 100-nm-thick n+-ZnO bottom layer (n = 8 × 1019 cm−3) and a 20-nm-thick n-ZnO top layer (n = 3 × 1016 cm−3) significantly improve the power conversion efficiency (PCE) of the CQDSCs by a factor of ~35% compared to the device with single-layered n- ZnO. Open-circuit photovoltage decay (OCVD) measurements prove that the graded energy alignment of ZnO DETL effectively reduces both interfacial and trapping-assisted charge recombination, relative to the single-layered ZnO. The facile Ar-pressure tuning method makes the energy-band alignment process more convenient and sheds a light on the application of DETL electrons transport layer, fabricated by the universal technique of magnetron sputtering. [ABSTRACT FROM AUTHOR]

• MoSe 2 were prepared by hydrothermal, ultrasonic and microwave irradiation methods. • Hydrothermal method influences the crystalline size, morphology, band gap and surface area. • MoSe 2 :H served as electron transport layer affecting the photovoltaic performance. • MoSe 2 :H achieved higher efficiency of 8.47% than MoSe 2 :U,7.42% and MoSe 2 :U,6.74%. The present investigation utilizes three distinct techniques, including hydrothermal (MoSe 2 :H), ultrasonic (MoSe 2 :U) and microwave irradiation methods (MoSe 2 :M), to synthesise nanostructures of molybdenum diselenide (MoSe 2). Several analytical techniques were used to evaluate the effects of synthesis method on the physicochemical properties of MoSe 2. Hydrothermal synthesis of MoSe 2 enhances the performance of perovskite solar cells (PSCs) by strengthening the electron transport layer. The findings show that the hydrothermal method enhances the crystalline size, morphology and narrowed band gap, and increases the surface area, ultimately influencing photovoltaic performance. The efficiency of MoSe 2 PSCs fabricated through the hydrothermal method is 8.47% (MoSe 2 :H), surpassing the efficiency of ultrasonic (MoSe 2 :U,7.42%) and microwave irradiation methods (MoSe 2 :U,6.74%). [ABSTRACT FROM AUTHOR]

As a new generation of photovoltaics, perovskite solar cells (PSCs) have been intensively studies in recent years due to their high-efficiency, low-cost and ease of fabrication. For a typical high-performance PSC, electron transport layer (ETL) plays an important role in selectively extracting and transporting photo-generated electrons from perovskite to the electrode. In this paper, for the first time, we found that a well-organized In 2 S 3 nanoflakes array can be used in PSCs with a high power conversion efficiency (PCE) of 18.22% with less hysteresis. In comparison, PSCs based on TiO 2 ETL showed a much lower PCE of 15.70%. Experimental results clearly illustrate that the optimized band structure, enhanced light tapping and low recombination of photo-generated carriers in In 2 S 3 ETL based devices leads to this enhanced performance. Noteworthily, such In 2 S 3 ETLs are simple and solution processable at low-temperature (≤80 °C), which might provide new avenue for low-cost and solution-processed photovoltaics. [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]

Abstract Vertical ZnO nanorod arrays were synthesized by a polymer template method and modified by TiO 2 shell via a sol-gel method. The core-shell structure of ZnO-TiO 2 nanorod arrays was used as an electron transport layer (ETL) of perovskite solar cells (PSCs) and the length of the nanorod arrays was controlled by changing the hydrothermal growth time. The photovoltaic performance of the PSC prepared in ambient atmosphere was found to be crucially dependent on the length of ZnO-TiO 2 nanorod arrays. ZnO-TiO 2 nanorod arrays with a suitable length enabled complete infiltration of CH 3 NH 3 PbI 3 perovskite into nanorod arrays and an increasement of carrier lifetime, eventually resulting in better cell performance. The PSC based on ZnO-TiO 2 nanorod arrays with the length of 600 nm shows a power conversion efficiency of 10.24% under ambient air (RH~40%, 25 °C), which is higher than the mean level of previous report. Meanwhile, the PCE of the unencapsulated device based on ZnO-TiO 2 nanorod arrays retains 80% of the initial efficiency after 7 days in ambient atmosphere. This work provides the potential application of ZnO-TiO 2 nanorod arrays with a suitable length as an effective ETL of efficient and stable all-solid-state PSCs. [ABSTRACT FROM AUTHOR]

In semi-transparent perovskite solar cells (PSCs) comprising a sputtered top electrode, the minimisation of detrimental sputter damage and/or its curing by post-processing treatment is essential to reach high efficiencies. In this work, we investigate the influence of sputter damage and post-deposition annealing steps for different electron transport layers (ETLs) in PSCs without the need of a protective buffer layer such as tin oxide deposited by atomic layer deposition. We compare solution-processed 6,6-Phenyl C61 butyric acid methyl ester (PCBM) to thermally evaporated C 60 , each in combination with a bathocuproine (BCP) layer deposited by spin coating or thermal evaporation including a thickness variation. In general, we find that C 60 is more resilient against sputter damage and thus C 60 -based cells show higher as-grown power conversion efficiencies (PCEs). Post-deposition annealing of the complete cell stack increases the PCE further to values > 16 % on 0.5 cm2 active area. However, we observe that the remaining solvent in the spin-coated PCBM layer is highly beneficial for the curing of the sputter damage during post-deposition annealing and we achieve even higher PCEs for cells incorporating solution-processed PCBM with up to > 18 % on 0.5 cm2. We show an alternative way to reach high efficiency semi-transparent perovskite solar cells without using thermally evaporated C 60 and/or a buffer layer like tin oxide deposited by atomic layer deposition (ALD). • Semi-transparent perovskite solar cells with PCE >18 % on 0.5 cm2 active area and a absorber bandgap of 1.63 eV. • No protective buffer layer like ALD-SnOx between ETL and sputtered TCO. • Curing of sputter damage with a short post-deposition annealing step at 90 °C. • Small residues of solvent in PCBM layer are detected by ToF-SIMS and are of great importance for the curing of sputter damage. • Investigating the influence of the ETL deposition method on as-grown efficiencies and post-deposition annealing behaviour. [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 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]

An electron transport layer (ETL) is essential for charge separation and electron extraction in perovskite solar cells (PSCs). In this work, we develop an efficient electron transport layer material SnO 2 -PMo 12 composite for the fully printable hole transport material (HTM)-free PSCs, in which PMo 12 denotes the Keggin-type polyoxometalate H 3 PMo 12 O 40 . Benefitting from the synergistic effect of polyoxometalates, SnO 2 -PMo 12 shows enhanced electron mobility, faster electron extraction and proper downward shift of the conduction band minimum, which boosts the injection and transfer of electrons from the perovskite to the ETL and effectively suppresses charge recombination. In addition, the hysteresis-free behavior appears in the SnO 2 -PMo 12 device, suggesting a remarkable improvement in photovoltaic performance and device stability. Compared to the conventional TiO 2 ETL, the average power conversion efficiency of the device with SnO 2 -PMo 12 ETL is boosted from 10.1% to 12.6%. This work brings a new insight into the promoting photovoltaic performance and stability of the fully printable HTM-free PSCs. [ABSTRACT FROM AUTHOR]

The need for an excellent electron transport layer (ETL) material is immensely significant for higher conversion efficiency of perovskite solar cells (PSCs). This work centers on the exceptional performance achieved by the Al-doped ZnO (AZO) ETL with reference to undoped ZnO (ZnO). Both doped and undoped ETL materials were synthesized and characterized to determine their structural, morphological, and optical behavior. In this work, solar cell performance of two similar CsPbIBr 2 -based PSCs with different ETLs namely FTO/ZnO/CsPbIBr 2 /NiO (Cell #1) and FTO/AZO/CsPbIBr 2 /NiO (Cell #2) are investigated through numerical simulation method. The obtained characteristics affirms that Cell #2 offers sufficient better performance parameters (J sc , V oc , FF, and η ) against Cell #1 with respect to variation in CsPbIBr 2 PVT, ETL and HTL thickness. The adverse effect on J-V characteristics caused by controllable introduction of defect density (N t) in PVT layer is negligible for Cell #2 compared to its ZnO counterpart. Further, the contribution of AZO ETL layer on cell's performance is evaluated in terms of variation in respective ETL and HTL thickness. The investigation reveals that Cell #2 offers a desirable η of 19.46% at electron capture cross section of 2 × 10−15 cm2 while Cell #1 delivers only 12.48%. • Highly conductive Al-doped zinc oxide (AZO) layer was synthesized using a solution process. • The performance of all-inorganic perovskite solar cells was determined using simulation. • By applying an AZO electron transport layer, over 19 % efficiency was achieved for perovskite solar cells. [ABSTRACT FROM AUTHOR]

• For the first time, SrLaInO 4 was used as an electron transport material in thin film solar cells. • The photoelectric properties of the photoanode were adjusted by Fe doping, and the charge recombination was reduced. • A high open-circuit voltage of 0.801 V was achieved for DSC based on Fe-doped SrLaInO 4 electron transport layer under AM 1.5G. This study presents the synthesis of SrLaInO 4 perovskite oxides using a high-temperature solid-phase method under atmospheric pressure, with varying Fe-doping concentrations incorporated during fabrication. The synthesized particles underwent characterization using X-ray diffraction and electron microscopy, revealing a layered crystal structure. X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy were employed to confirm the successful incorporation of Fe into the SrLaInO 4 crystal structure. Significantly, Fe-doping was observed to broaden the light absorption range of the perovskite oxide whilst simultaneously reducing the bandgap. When employed as the electron transport layer in dye-sensitized solar cells, Fe-doped SrLaInO 4 perovskite exhibited a maximum efficiency of 4.64%, alongside an open-circuit voltage (V OC) of 0.801 V, which was noticeably higher than that observed in identically-prepared cells employing TiO 2 as the electron transport layer. [ABSTRACT FROM AUTHOR]