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This study investigated the fabrication and characterization of CH3NH3PbI3 based perovskite solar cells (PSCs) using the one-step spin coating technique under ambient conditions, eliminating the need for expensive glovebox and thermal evaporation equipment. The perovskite layer was annealed at 65 °C for 30 seconds and 100 °C for 30 seconds, 1 and 2 minutes. The scanning electron microscope (SEM) images show a smooth and uniform surface coverage for the ETL and CH3NH3PbI3 layers. SEM results also show an average grain size of 397 nm for CH3NH3PbI3 and an average particle size of ~17 nm for TiO2 was confirmed by transmission electron microscopy (TEM). X-ray diffraction (XRD) results confirmed the formation of tetragonal perovskite (CH3NH3PbI3) phase with high crystallinity with a crystallite size of 19.99 nm for the samples annealed for 30 seconds at 65 °C and 1 min at 100 °C. FTIR results also confirmed the presence of anatase TiO2 at wavenumber 438 cm-1 and the formation of the adduct of Pb2 with dimethyl sulfoxide (DMSO) and MAI is confirmed at 1,015 cm-1. From the Tauc plot the bandgap energy of TiO2 and Perovskite layers was determined to be 3.52 eV and 2.06 eV respectively. An open-circuit voltage was 0.9057 V and short circuit current density was 12.2185 mA/cm² with a fill factor of 48.05 and power conversion efficiency (PCE) of 5.199%. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) have gained much attention in recent years because of their improved energy conversion efficiency, simple fabrication process, low processing temperature, flexibility, light weight, and low cost of constituent materials when compared with their counterpart silicon based solar cells. Besides, stability and toxicity of PSCs and low power conversion efficiency have been an obstacle towards commercialization of PSCs which has attracted intense research attention. In this research paper, a Glass/Cu2O/CH3NH3SnI3/ZnO/Al inverted device structure which is made of cheap inorganic materials, n-type transparent conducting oxide (TCO)-free, stable, photoexcited toxic-free perovskite have been carefully designed, simulated and optimized using a one-dimensional solar cell capacitance simulator (SCAPS-1D) software. The effects of layers' thickness, perovskite's doping concentration and back contact electrodes have been investigated, and the optimized structure produced an open circuit voltage (Voc) of 1.0867 V, short circuit current density (JSC) of 33.4942 mA/cm2, fill factor (FF) of 82.88% and power conversion efficiency (PCE) of 30.17%. This paper presents a model that is first of its kind where the highest PCE performance and eco-friendly n-type TCO-free inverted CH3NH3SnI3 based perovskite solar cell is achieved using all-inorganic transport materials. [ABSTRACT FROM AUTHOR]

Zinc oxide (ZnO), a material with excellent electron mobility and a low-temperature requirement for production, is a promising option for use as an electron transport layer in perovskite solar cells (PSCs). However, it does have the drawback of having a low open-circuit voltage (VOC). Herein, to increase the VOC parameter of ZnO-based PSCs, graphene quantum dots (GQDs) are incorporated into the ZnO precursor and used as desirable ETL for PSCs. The presence of GQDs in ZnO ETL facilitated photo-electrons at the ETL/perovskite interface by reducing charge transfer resistance in this interface. Compared to the net ZnO-based PSCs, solar cells using GQD-doped ZnO as ETL have better stability, comparable JSC, higher VOC, and FF. The best GQD-doped-ZnO ETL-based PSCs recorded the highest power conversion efficiency of 20.23% with VOC of 1.130V. Meanwhile, the boosted PCE of FAPbI3-based PSCs is achieved due to the improved perovskite crystal quality, the effective defect passivation effect of GQDs at ZnO/FAPbI3 interface, and the increased electrical conductivity of ZnO ETL. In addition, the GQD-doped ETL devices showed higher ambient air stability than the devices with net ZnO ETLs. [ABSTRACT FROM AUTHOR]

At present, heavy-metal-free quantum dot light-emitting diodes (QLEDs) have shown great potential as a research hotspot in the field of optoelectronic devices. This article reviews the research on heavy-metal-free quantum dot (QD) materials and light-emitting diode (LED) devices. In the first section, we discussed the hazards of heavy-metal-containing quantum dots (QDs), such as environmental pollution and human health risks. Next, the main representatives of heavy-metal-free QDs were introduced, such as InP, ZnE (E=S, Se and Te), CuInS2, Ag2S, and so on. In the next section, we discussed the synthesis methods of heavy-metal-free QDs, including the hot injection (HI) method, the heat up (HU) method, the cation exchange (CE) method, the successful ionic layer adsorption and reaction (SILAR) method, and so on. Finally, important progress in the development of heavy-metal-free QLEDs was summarized in three aspects (QD emitter layer, hole transport layer, and electron transport layer). [ABSTRACT FROM AUTHOR]

Highlights: Developing a universal strategy of the p–n homojunction engineering that could significantly boost electron mobility of electron transport layer (ETL) by two orders of magnitude. Proposing a new mechanism based on p–n homojunction to explain inhibited carrier loss at buried interface. Setting a new performance benchmark as high as 25.50% for planar perovskite solar cells employing TiO2 as ETLs. Low-temperature processed electron transport layer (ETL) of TiO2 that is widely used in planar perovskite solar cells (PSCs) has inherent low carrier mobility, resulting in insufficient photogenerated electron transport and thus recombination loss at buried interface. Herein, we demonstrate an effective strategy of laser embedding of p-n homojunctions in the TiO2 ETL to accelerate electron transport in PSCs, through localized build-in electric fields that enables boosted electron mobility by two orders of magnitude. Such embedding is found significantly helpful for not only the enhanced crystallization quality of TiO2 ETL, but the fabrication of perovskite films with larger-grain and the less-trap-states. The embedded p–n homojunction enables also the modulation of interfacial energy level between perovskite layers and ETLs, favoring for the reduced voltage deficit of PSCs. Benefiting from these merits, the formamidinium lead iodide (FAPbI3) PSCs employing such ETLs deliver a champion efficiency of 25.50%, along with much-improved device stability under harsh conditions, i.e., maintain over 95% of their initial efficiency after operation at maximum power point under continuous heat and illumination for 500 h, as well as mixed-cation PSCs with a champion efficiency of 22.02% and over 3000 h of ambient storage under humidity stability of 40%. Present study offers new possibilities of regulating charge transport layers via p-n homojunction embedding for high performance optoelectronics. [ABSTRACT FROM AUTHOR]

Titanium dioxide ( TiO 2 ) is a commonly employed electron transport layer in perovskite solar cells (PSCs) due to its exceptional attributes such as high mobility, a wide bandgap and remarkable stability against moisture and high temperatures. This holds particularly true for inorganic PSCs. Nevertheless, the substantial hysteresis and elevated trap defect levels following annealing present challenges to enhance the efficiency of the PSCs. Herein, we proposed a chemical bath deposition (CBD) method to fabricate the TiO 2 layer, serving as the electron transport layer in CsPbBr 3 solar cells. This method is coupled with KCl, which supplies an ample quantity of K ions capable of diffusing into the CsPbBr 3 perovskite film during the annealing process. The inclusion of K ions significantly diminishes the solar cell hysteresis and enhances the crystalline quality of the perovskite material, thereby enhancing the performance of CsPbBr 3 solar cells. By implementing the TiO 2 and KCl treatments, we achieved an impressive efficiency of 9.49%. Furthermore, the device also exhibited excellent stability in air for 30 days. We introduced KCl as a buffer layer to improve the quality of the TiO 2 films, which was used as the electron transport layer in CsPbBr 3 perovskite solar cells. This strategic addition of K ions serves not only to alleviate hysteresis in the perovskite solar cells, but also to enhance the crystallinity of the perovskite material. These cells have achieved an impressive champion efficiency of 9.49%, while maintaining their performance for over 30 days in ambient conditions. [ABSTRACT FROM AUTHOR]

Context: Density functional theory (DFT) calculations are carried out on pure and doped rutile TiO 2 . The bandgap (E g ) for pristine, S-doped, Fe-doped, and Fe/S co-doped materials is direct, with values of 2.98 eV, 2.18 eV, 1.58 eV, and 1.40 eV. The effective mass of charge carriers (m*) and ratio of effective masses of holes to effective masses of electrons (R) are also investigated, and it is discovered that Fe/S co-doped materials have the lowest charge carrier recombination rate. The Fe/S co-doped material has the highest ε (ω) . α (ω) of doped materials shifted into the visible range. Due to the high dopant concentration in Fe and Fe/S-doped cases, the E g is lowered to a relatively small value; hence, only pristine and S-doped materials are verified as electron transport layer (ETL). A solar cell device analysis employing pure and S-doped rutile TiO 2 as ETL is completed using DFT-derived parameters in SCAPS-1D modeling software for the first time. For the optimized solar cells, current–voltage (IV) characteristics, quantum efficiency (QE), capacitance-voltage (CV) characteristics, and capacitance-frequency (Cf) characteristics are provided. The aim of the present study is to improve efficiency of perovskite solar cell by doping as well as to improve accuracy of simulation by applying DFT extracted parameters as input. From the analysis, improvement is found in efficiency of doped TiO 2 compared to un-doped TiO 2 . The efficiency of the PSC with S-doped ETL is 1.418% higher than the PSC with un-doped ETL. Method: Quantumwise Automistic Tool Kit (ATK) is used to extract DFT parameters. Using these DFT parameters as input in SCAPS-1D (Solar Cell Capacitance Simulator), solar cells for doped and un-doped material are simulated. The density functional theory (DFT)-based orthogonalized linear combination of atomic orbital (OLCAO) technique is used. Structural optimization is done using the LBFGS (Limited-memory Broyden-Fletcher-Goldfarb-Shanno). PBESol-GGA (Perdew-Burke-Ernzerhof solid-generalized gradient approximation) is applied as exchange correlation for calculating structural parameters, while MGGA-TB09 (meta-generalized gradient approximation-Tran and Blaha) is applied as exchange correlation for calculating optical and electronic properties. [ABSTRACT FROM AUTHOR]

Compared to organic–inorganic hybrid perovskites, the cesium‐based all‐inorganic lead halide perovskite (CsPbI3) is a promising light absorber for perovskite solar cells owing to its higher resistance to thermal stress. Nonetheless, additional research is required to reduce the nonradiative recombination to realize the full potential of CsPbI3. Here, the diffusion of Cs ions participating in ion exchange is proposed to be an important factor responsible for the bulk defects in γ‐CsPbI3 perovskite. Calculations based on first‐principles density functional theory reveal that the [PbI6]4− octahedral tilt modifies the perovskite crystallographic properties in γ‐CsPbI3, leading to alterations in its bandgap and crystal strain. In addition, by substituting amorphous barium titanium oxide (a‐BaTiO3) for TiO2 as the electron transport layer, interfacial defects caused by imperfect energy levels between the electron transport layer and perovskite are reduced. High‐resolution transmission electron microscopy and electron energy loss spectroscopy demonstrate that a‐BaTiO3 forms entirely as a single phase, as opposed to Ba‐doped TiO2 hybrid nanoclusters or separate domains of TiO2 and BaTiO3 phases. Accordingly, inorganic perovskite solar cells based on the a‐BaTiO3 electron transport layer achieved a power conversion efficiency of 19.96%. [ABSTRACT FROM AUTHOR]

Abstract When implementing optoelectronic devices through the stacking of heterogeneous materials, considering the bandgap offset is crucial for achieving efficient carrier dynamics. In this study, the bandgap offset characteristics are investigated when n‐type gallium nitride nanowires (n‐GaN NWs) are used as electron transport layers in methylammonium lead iodide (MAPbI3)‐based optoelectronic devices. n‐GaN NWs are grown on indium‐tin‐oxide (ITO)‐coated glass via the plasma‐assisted molecular beam epitaxy (PA‐MBE) process to form the “GaN NWs‐on‐glass” platform. A MAPbI3 thin film is then spin‐coated on the GaN NWs‐on‐glass. X‐ray photoelectron spectroscopy (XPS) shows that the valence and conduction band offsets in the MAPbI3/n‐GaN heterostructure are 2.19 and 0.40 eV, respectively, indicating a type‐II band alignment ideal for optoelectronic applications. Prototype photovoltaic devices stacking perovskite on GaN NWs‐on‐glass show excellent interfacial charge‐transfer ability, photon recycling, and carrier extraction efficiency. As a pioneering step in exploiting the diverse potential of the GaN‐on‐glass, it is demonstrated that the junction characteristics of MAPbI3/n‐GaN NW heterostructures can lead to a variety of optoelectronic device applications.

Abstract Sol–gel processed zinc oxide (ZnO) is one of the most widely used electron transport layers (ETLs) in inverted organic solar cells (OSCs). The high annealing temperature (≈200 °C) required for sintering to ensure a high electron mobility however results in severe damage to flexible substrates. Thus, flexible organic solar cells based on sol–gel processed ZnO exhibit significantly lower efficiency than rigid devices. In this paper, an indium‐doping approach is developed to improve the optoelectronic properties of ZnO layers and reduce the required annealing temperature. Inverted OSCs based on In‐doped ZnO (IZO) exhibit a higher efficiency than those based on ZnO for a range of different active layer systems. For the PM6:L8‐BO system, the efficiency increases from 17.0% for the pristine ZnO‐based device to 17.8% for the IZO‐based device. The IZO‐based device with an active layer of PM6:L8‐BO:BTP‐eC9 exhibits an even higher efficiency of up to 18.1%. In addition, a 1.2‐micrometer‐thick inverted ultrathin flexible organic solar cell is fabricated based on the IZO ETL that achieves an efficiency of 17.0% with a power‐per‐weight ratio of 40.4 W g−1, which is one of the highest efficiency for ultrathin (less than 10 micrometers) flexible organic solar cells.

Perovskite solar cells (PSCs) have experienced an unprecedented advancement in the last decade owing to their astonishingly attractive properties, especially high-power conversion efficiency (PCE). In this study, the influence of reduced graphene oxide (rGO) on the photovoltaic performance of perovskite solar cells prepared via solution processes-based spin coating method was investigated. X-ray Diffraction (XRD), Fourier Transform Infrared spectrometer (FTIR), UV-visible spectrophotometry, Scanning Electron Microscopy (SEM) were used to study the properties of the prepared films. ITO/MAPbBr3/Gr and ITO/rGO/MAPbBr3/Gr planar PSCs were fabricated via spin coating method. ITO/rGO/MAPbBr3/Gr film achieved a power conversion efficiency (PCE) of 4.1 short circuit current (Jsc) of 7.5 mAcm−2 and fill factor (FF) of 61.2% compared to a PCE of 3.6%, Jsc of 6.6 mAcm−2 and FF of 58.0% achieved compared to PCE of 3.6%, %, Jsc of 6.6 mAcm−2 and FF of 58.0% achieved by ITO/MAPbBr3/Gr film. The PSC demonstrated the percentage enhancement value of 16.80% when modified with rGO. This study shows that rGO generated functional groups that act as conducting bridge in reducing the contact resistance between interface of the device.

Abstract The buried interface between the electron transport layer (ETL) and the perovskite layer plays a crucial role in enhancing the power conversion efficiency (PCE) and stability of n–i–p type perovskite solar cells (PSCs). In this study, the interface between the chemical bath deposited (CBD) titanium oxide (TiO2) ETL and the perovskite layer using multi‐functional potassium trifluoromethyl sulfonate (SK) is modified. Structural and elemental analyses reveal that the trifluoromethyl sulfonate serves as a crosslinker between the TiO2 and the perovskite layer, thus improving the adhesion of the perovskite to the TiO2 ETL through strong bonding of the ─CF3 and ─SO3− terminal groups. Furthermore, the multi‐functional modifiers reduced interface defects and suppressed carrier recombination in the PSCs. Consequently, devices with a champion PCE of 25.22% and a fill factor (FF) close to 85% is achieved, marking the highest PCE and FF observed for PSCs based on CBD TiO2. The unencapsulated device maintained 81.3% of its initial PCE after operating for 1000 h.

High power conversion efficiency (PCE) flexible perovskite solar cells (FPSCs) are highly desired power sources for aerospace crafts and flexible electronics. However, their PCEs still lag far behind their rigid counterparts. Herein, we report a high PCE FPSC by controllable growth of a SnO2 electron transport layer through constant pH chemical bath deposition (CBD). The application of SnSO4 as tin source enables us to perform CBD without strong acid, which in turn makes it applicable to acid-sensitive flexible indium tin oxide. Furthermore, a mild and controllable growth environment leads to uniform particle growth and dense SnO2 deposition with full coverage and reproducibility, resulting in a record PCE of up to 25.09% (certified 24.90%) for FPSCs to date. The as-fabricated FPSCs exhibited high durability, maintaining over 90% of their initial PCE after 10000 bending cycles.

Abstract MXenes, a class of two-dimensional (2D) transition metal carbides and nitrides, have a wide range of potential applications due to their unique electronic, optical, plasmonic, and other properties. SnO2–Ti3C2 MXene with different contents of Ti3C2 (0.5, 1.0, 2.0, 2.5 wt‰), experimentally, has been used as electron transport layers (ETLs) in Perovskite Solar Cells (PSCs). The SCAPS-1D simulation software could simulate a perovskite solar cell comprised of CH3NH3PbI3 absorber and SnO2 (or SnO2–Ti3C2) ETL. The simulation results like Power Conversion Efficiency (PCE), Open circuit voltage (VOC), Short circuit current density (JSC), Fill Factor (FF), and External Quantum Efficiency (EQE) have been compared within samples with different weight percentages of Ti3C2 MXene incorporated in ETL. Reportedly, the ETL of SnO2 with Ti3C2 (1.0 wt‰) effectively increases PCE from 17.32 to 18.32%. We simulate the role of MXene in changing the ideality factor (nid), photocurrent (JPh), built-in potential (Vbi), and recombination resistance (Rrec). The study of interface recombination currents and electric field shows that cells with 1.0 wt‰ of MXene in SnO2 ETL have higher values of ideality factor, built-in potential, and recombination resistance. The correlation between these values and cell performance allows one to conclude the best cell performance for the sample with 1.0 wt‰ of MXene in SnO2 ETL. With an optimization procedure for this cell, an efficiency of 27.81% is reachable.

Abstract In recent years, the power conversion efficiency (PCE (%)) of perovskite solar cells (PSCs) has improved to over 26%. To enhance the photovoltaic properties of PSCs, several materials for the electron transport layer (ETL) have been investigated. Zinc oxide (ZnO) is a significant ETL due to its high electron mobility and optical transparency in PSCs. As a result of various deposition methods, ZnO ETL can be processed at low temperatures. On the other hand, based on several studies, metal-doped ZnO can facilitate electron transfer, thereby improving the performance of un-doped ZnO ETL-based PSCs. Here, to improve the PCE (%) and long-term stability of un-doped ZnO ETL-PSCs, silver (Ag)-doped ZnO 1wt% as a buffer layer is examined. In this paper, with the addition of an organic solvent (ethanol) to the dispersion of Ag-doped ZnO 1 wt% nanoparticles (NPs) in deionized (DI) water, the morphology of the buffer layer (Ag-doped ZnO 1 wt%) can be controlled. This approach focuses on reducing the wettability of the ZnO/Ag-doped ZnO 1 wt% bilayer ETLs and enhancing the stability of un-doped ZnO ETL-PSCs. According to the results, the ZnO/H2O-ethanol mixtures-Ag-doped ZnO 1 wt% bilayer ETL leads to the formation of high-quality perovskite with low defects, reducing the recombination rate, and long-term stability of un-doped ZnO ETL-PSCs in ambient conditions.

This article reviews the latest advancements in perovskite solar cell (PSC) components for innovative photovoltaic applications. Perovskite materials have emerged as promising candidates for next-generation solar cells due to their exceptional light-absorbing capabilities and facile fabrication processes. However, limitations in their stability, scalability, and efficiency have hindered their widespread adoption. This review systematically explores recent breakthroughs in PSC components, focusing on absorbed layer engineering, electron and hole transport layers, and interface materials. In particular, it discusses novel perovskite compositions, crystal structures, and manufacturing techniques that enhance stability and scalability. Additionally, the review evaluates strategies to improve charge carrier mobility, reduce recombination, and address environmental considerations. Emphasis is placed on scalable manufacturing methods suitable for large-scale integration into existing infrastructure. This comprehensive review thus provides researchers, engineers, and policymakers with the key information needed to motivate the further advancements required for the transformative integration of PSCs into global energy production.

Electron transport layer (ETL) is a crucial part for perovskite solar cells (PSCs). However, leakage current and oxygen vacancies result from little pores grown from sol‐gel method would inevitably deteriorate the performance of ETL. In contrast, thin films prepared by chemical bath deposition (CBD) could significantly restrain the little cracks. Here, SnO2 ETL are prepared by optimized CBD process, sodium citrate (SC) is explored as an auxiliary reagent to disperse ETL, thus enhances the smoothness and conductivity of the ETL, resulting in a pore‐free flat surface morphology and decreased oxygen vacancy, which is favorable for electron transport and deposition of perovskite (PVK). The PVK film fabricated on the oxygen vacancy free substrate demonstrates high quality and decreased defect density, thus effectively prevents the non‐radiative recombination of carriers. As a result, the short‐circuit current (JSC) and open circuit voltage (Voc) of the PSC devices have been obviously improved, leading to increased photoelectric conversion efficiency from 21.03% to 22.04%. Meanwhile, the long‐term and moisture stability have been promoted simultaneously. [ABSTRACT FROM AUTHOR]

SnO2 nanoparticles (NPs) have been used as an electron transport layer (ETL) in quantum dot light-emitting diodes (QLEDs) to achieve stable and high-performance devices. However, SnO2 NPs with high electron mobility cause the problem of imbalanced charge injection and transport in QLEDs. Meanwhile, the SnO2 NPs synthesized at low temperature have hydroxyl (−OH) groups, which could damage the performance of QLEDs. Here, Zn doping was applied to modulate the properties of SnO2 NPs and achieve better carrier balance in green CdSe/ZnS QLED. The maximum current efficiency (CE) of QLED with 5 wt % Zn-doped SnO2 NPs is 2.3-fold higher than that of SnO2-based QLED. In addition, a small-molecule 4,4′-bis-(carbazole-9-yl)-1,1′-biphenyl (CBP)-mixed poly-(9-vinylcarbazole) (PVK) layer was used as a hole transport layer to facilitate the hole injection and charge balance. As a result, a maximum external quantum efficiency (EQE) of 5.03% is obtained for the best performance device. The T50 lifetime at a luminance of 100 cd/m2, for a device based on 5 wt % Zn-doped SnO2 ETL, is 9141 h, which is 2.29-fold longer than the reference one. This work provides a new strategy to obtain high-performance and stable display arrays. [ABSTRACT FROM AUTHOR]

Operational stability is the main obstacle to the industrial applications of organic solar cells (OSCs). In this study, different degradation mechanisms under continuous simulated solar radiation are demonstrated for high‐performance non‐fullerene OSCs based on commonly used electron transport materials, i.e., ZnO and SnO2. The ZnO‐induced decomposition pathways of A‐DA'D‐A type non‐fullerene acceptors (NFAs) under UV illumination are unraveled for the first time and related to N‐dealkylation of pyrrole from the core moiety. In the case of SnO2, poor photo‐stability is primarily ascribed to a high density of trap states, which can be diminished by surface modification to achieve better device stability that is comparable with the stability under LED illumination without UV components. With a thorough understanding of the degradation pathways, this study provides valuable guidelines for designing high‐performance and stable non‐fullerene OSCs. [ABSTRACT FROM AUTHOR]

Quantum dot light‐emitting diodes (QLEDs) is one of the most important components in the display field, and different structures have a certain impact on the final performance of the device. Previous QLEDs mainly use ZnO nanocrystals as the electron transport layer (ETL), but the chemical activity of ZnO nanocrystals under electric fields and moisture is not stable enough. To solve this problem, this paper studies the effects of TiO2 films with different thicknesses on the luminescence, current density and external quantum efficiency of QLED devices by using magnetron sputtered TiO2 as a new ETL. The experimental results show that the 50nm TiO2 film achieves the highest external quantum efficiency while maintaining favorable current density and brightness. [ABSTRACT FROM AUTHOR]

The presence of carrier traps, originating from oxygen vacancies in the electron transport layer (ETL), significantly impacts both the efficiency and power hysteresis of perovskite solar cells. This study successfully demonstrated that the incorporation of molybdenum (Mo) dopants into the SnO2 ETL effectively mitigates carrier traps, leading to an enhancement in the power conversion efficiency of perovskite solar cells prepared under ambient conditions. The process of Mo doping in SnO2 involves a straightforward application of molybdenum salt onto the SnO2 layer via spin coating, followed by annealing at 185 °C for 1 h. Raman analysis reveals that the presence of Mo in the SnO2 lattice resulted in subtle modifications to the in-plane Sn–O stretching mode vibration (Eg), modifying the optoelectrical properties of SnO2. The champion Mo–SnO2 ETL based perovskite solar cells exhibits an impressive power conversion efficiency as high as 7.33% with Voc, Jsc and FF as high as 0.88 V, 16.02 mA/cm−2, and 0.52, respectively. It is significantly higher than the pristine SnO2 ETL based device. These figures represent a significant advancement over devices employing pristine SnO2 ETLs. An analysis of power hysteresis indicated that the utilization of Mo-doped SnO2 ETLs effectively reduced hysteresis effects in the devices, suggesting efficient defect passivation within the device structure. These findings highlight the promising potential of Mo-doped SnO2 ETLs for applications in perovskite solar cells with low power hysteresis. [ABSTRACT FROM AUTHOR]

Substandard printing quality of electron transport layers (ETLs) always leads to non‐ideal nucleation crystallization and bottom interface contact of the perovskite, followed by the formation of poor‐quality perovskite films with severe heterogeneity, which is the major source of non‐radiative recombination loss and environmental sensitivity of perovskite solar cells (PVSCs). These often result in serious photovoltaic performance loss, significant instability, and negative fabrication reproducibility. Herein, sodium phytate is proposed as a chelating agent for passivating the tin oxide (SnO2) ETLs to enable the stabilization of SnO2 nanoparticles and facilitate the printing of pinhole‐free films, thereby realizing the controlled nucleation crystallization in perovskite precursor. Thus, the printed PVSCs exhibit a champion power conversion efficiency up to 23.77% with negligible hysteresis effect. The unencapsulated devices demonstrate outstanding long‐term stability, which maintains over 80% of their initial efficiency under exposure to atmospheric environment (50% relative humidity) for 1500 hours, and a consistent and centralized distribution of efficiencies across all seasons, indicating their good reproducibility in diverse climatic atmospheres. [ABSTRACT FROM AUTHOR]

Not only can perovskite solar cells be exposed to high temperatures, up to 80 °C, depending on the operating environment, but absorbed energy is lost as heat, so it is important to have thermal stability for commercialization. However, in the case of the recently reported p-i-n structure solar cell, most of the electron and hole transport layers are composed of organic materials vulnerable to heat transfer, so the light absorption layer may be continuously exposed to high temperatures when the solar cell is operated. In this study, we attempted to improve the thermal conductivity of the electron transport layer using phenyl-C61-butyric acid methyl ester (PCBM) containing zinc oxide (ZnO). As a result, the thermal conductivity was improved by more than 7.4% and 23.5% by adding 6.57vol% and 22.38vol% of ZnO to PCBM, respectively. In addition, the insertion of ZnO resulted in changes in the electron transport behavior and energy level of the electron transport layer. As a result, it was confirmed that not only could the temperature stability of the perovskite thin film be improved, but the efficiency of the solar cell could also be improved from 14.12% to 17.97%. [ABSTRACT FROM AUTHOR]

Perovskite solar cell (pero‐SC) has attracted extensive studies as a promising photovoltaic technology, wherein the electron extraction and transfer exhibit pivotal effect to the device performance. The planar SnO2 electron transport layer (ETL) has contributed the recent record power conversion efficiency (PCE) of the pero‐SCs, yet still suffers from surface defects of SnO2 nanoparticles which brings energy loss and phase instability. Herein, we report a localized oxidation embellishing (LOE) strategy by applying (NH4)2CrO4 on the SnO2 ETL. The LOE strategy builds up plentiful nano‐heterojunctions of p‐Cr2O3/n‐SnO2 and the nano‐heterojunctions compensate the surface defects and realize benign energy alignment, which reduces surface non‐radiative recombination and voltage loss of the pero‐SCs. Meanwhile, the decrease of lattice mismatch released the lattice distortion and eliminated tensile stress, contributing to better stability of the devices. The pero‐SCs based on α‐FAPbI3 with the SnO2 ETL treated by the LOE strategy realized a PCE of 25.72 % (certified as 25.41 %), along with eminent stability performance of T90>700 h. This work provides a brand‐new view for defect modification of SnO2 electron transport layer. [ABSTRACT FROM AUTHOR]

The tetragonal crystal structured anatase titanium dioxide (TiO2) has been conventionally used as an electron transport layer in emerging solar cells. Conventionally, a high-temperature process above 450 °C is indispensable to form crystallized TiO2 films with a well-defined mesoporous structure. Due to the temperature limitations of the flexible polymer substrates, notably below 150 °C, such a high-temperature process is ineffective for flexible emerging solar cells. Currently, cutting-edge and high-potential solar cells are flexible dye-sensitized and perovskite solar cells which are preeminent in mass production due to their roll-to-roll printing technique. Hence, this study explores a low-temperature synthesis of crystallized TiO2 layers using the sol-gel method with various precursor concentrations of titanium tetraisopropoxide (TTIP). Then, the crystallized TiO2 was deposited with a simple yet low-cost spin-coat technique on flexible substrates (ITO/PET). A thorough scrutinization of TTIP concentration is crucial in identifying the potential of TiO2 films through comprehensive studies of elements aspects of structural, optical and electrical properties. The synthesized TiO2 films with a TTIP concentration of 0.5 M demonstrated a high porosity microstructure with exceptional transmittance, allowing a large number of photons to penetrate and thereby resulting in an enhanced charge carrier conduction mechanism. In addition, the direct optical bandgap is reduced with increasing TTIP molarity, proving the involvement of particle factors influencing photocatalytic activities. Moreover, electrical analysis proved that all the correlation features resulted in remarkably low sheet resistance and conductivity of 0.4 MΩ/sq and 0.1194 mS/cm, respectively. It can be conjectured from this study that the synthesis of crystallized TiO2 at low-temperature conditions with a certain TTIP molarity is successful and has resulted in an enhancement of the electron conduction mechanism, particularly for flexible emerging solar cell applications. Highlights: The TiO2 layer has been successfully synthesized by the sol-gel technique without the need for a subsequent conventional high-temperature annealing process, which enables the realization of fabrication for flexible emerging solar cells. A broad range of different titanium tetrapropoxide (TTIP) molarities have been optimized, resulting in sheet resistance comparable to conventional TiO2 layers subjected to a high annealing process. Furthermore, detailed studies from various aspects have also been critically analysed in terms of microstructure, optical and electrical properties to analyse the efficient charge carrier conduction mechanism. Last and foremost, sol-gel synthesized TiO2 with 0.5 M TTIP has shown remarkable features, paving the way for the fabrication of flexible PSC in the future. [ABSTRACT FROM AUTHOR]

This study uses computational analysis to comprehensively investigate lead‐free organic–inorganic CH3NH3SnI3 (MASnI3)‐based perovskite solar cells (PSCs). The optoelectronic properties of MASnI3 are investigated using density functional theory with first‐principles calculations, highlighting its potential for photovoltaic applications. Key findings include the determination of a crucial bandgap (0.97 eV), identification of the onset of photon absorption at energies exceeding 2 eV, and characterization of material properties, such as the absorption and extinction coefficients, reflectivity, and refractive index. Device optimization through simulations explores parameters such as layer thickness, defect density, and different charge transport layers, resulting in a remarkable enhancement in the power conversion efficiency to 16.72%. Additionally, this study focuses on the influence of the working temperature, series resistance (Rs), and shunt resistance (Rsh) on the photovoltaic device performance. Hence, a high photovoltaic efficiency in MASnI3‐based PSCs can be achieved by carefully optimizing the device performance parameters and effectively managing the defect densities. [ABSTRACT FROM AUTHOR]

The presence of TiO2 used as an efficient electron transport layer is crucial to achieving high-performance solar cells, especially for a hole transport material (HTM)-free carbon-based perovskite solar cell (PSC). The hydrolysis of TiCl4 is one of the most widely used routes for forming TiO2 layer in solar cells, which includes the stock solution preparation from TiCl4 initial precursor and the thermal hydrolysis of the stock solution. The second thermal hydrolysis step has been extensively studied, while the initial hydrolysis reaction in the first step is not receiving sufficient attention, especially for its influence on the photovoltaic performance of HTM-free carbon-based devices. In this study, the role of TiCl4 stock solution in the growth process of TiO2 layer is examined. Based on the analysis of the Ti(IV) intermediate states for different TiCl4 concentrations from Raman spectra, 2 M TiCl4 precursor exhibits moderate nucleation and growth kinetics without generating too many intermediates which occurs in 3 M TiCl4 precursor, yielding ∼300 nm size spherical TiO2 agglomerates with a rutile phase. In the aspect of devices, the HTM-free carbon-based PSCs fabricated using 2 M TiCl4 precursor deliver a conversion efficiency beyond 17%, which may be attributed to the reduced defect in compact TiO2 layer. [ABSTRACT FROM AUTHOR]

Perovskite solar cells show great potential application prospects in the field of solar cells due to their promising properties. However, most perovskite solar cells that exhibit excellent photovoltaic performance typically require a carrier transport layer that necessitates a high-temperature annealing process. This greatly restricts the scalability and compatibility of perovskite solar cells in flexible electronics. In this paper, SnO2 nanoparticles with high crystallinity, good dispersibility and uniform particle size distribution are first prepared using a solvothermal method and dispersed in n-butanol solution. SnO2 electron transport layers are then prepared by a low-temperature spin coating method, and the photovoltaic characteristics of perovskite solar cells prepared with different SnO2 nanoparticles/n-butanol concentrations are studied. Results indicate that the rigid perovskite solar cell achieves the highest power conversion efficiency of 15.61% when the concentration of SnO2 nanoparticles/n-butanol is 15 mg mL-1. Finally, our strategy is successfully applying on flexible perovskite solar cells with a highest PCE of 14.75%. Our paper offers a new possibility for large-scale preparation and application of perovskite solar cells in flexible electronics in the future. [ABSTRACT FROM AUTHOR]

In organic solar cells, the interfaces between the photoactive layer and the transport layers are critical in determining not only the efficiency but also their stability. When solution‐processed metal oxides are employed as the electron transport layer, the presence of surface defects can downgrade the charge extraction, lowering the photovoltaic parameters. Thus, understanding the origin of these defects is essential to prevent their detrimental effects. Herein, it is shown that a widely reported and commercially available colloidal SnO2 dispersion leads to suboptimal interfaces with the organic layer, as evidenced by the s‐shaped J–V curves and poor stability. By investigating the SnO2 surface chemistry, the presence of potassium ions as stabilizing ligands is identified. By removing them with a simple washing with deionized water, the s‐shape is removed and the short‐circuit current is improved. It is tested for two prototypical blends, TPD‐3F:IT‐4F and PM6:L8:BO, and for both the power conversion efficiency is improved up to 12.82% and 16.26%, from 11.06% and 15.17% obtained with the pristine SnO2, respectively. More strikingly, the stability is strongly correlated with the surface ions concentration, and these improved devices maintain ≈87% and ≈85% of their initial efficiency after 100 h of illumination for TPD‐3F:IT‐4F and PM6:L8:BO, respectively. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) have garnered significant attention in the photovoltaic field owing to their exceptional photoelectric properties, including high light absorption, extensive carrier diffusion distance, and an adjustable band gap. Temperature is a crucial factor influencing both the preparation and performance of perovskite solar cells. The annealing temperature exerts a pronounced impact on the device structure, while the operational temperature influences carrier transport, perovskite band gap, and interface properties. This paper provides a comprehensive review of the influence of varied annealing temperatures on the hole transport layer, electron transport layer, and perovskite layer. Additionally, we present an overview of innovative annealing methods applied to perovskite materials. The effects of diverse working temperatures on the overall performance of perovskite cells are thoroughly examined and discussed in this review. In the end, different temperature conditions under ISOS testing conditions are summarized. [ABSTRACT FROM AUTHOR]

Tin oxide (SnO2) and aluminum-doped zinc oxide (AZO) have been recognized as promising materials for the electron transport layer (ETL) in perovskite solar cells (PSCs) due to their favorable optoelectronic properties and low-temperature deposition processes. However, high surface trap density at the ETL/perovskite interface limits the further improvement of the power conversion efficiency (PCE) of planar PSCs. Herein, we have demonstrated a simple surface treatment of low-temperature deposited SnO2/AZO–ETL through mono-ethanolamine (MEA) to passivate the defects at the AZO/perovskite interface and reduce carrier recombination. Meanwhile, after MEA modification, the defect states at the AZO/perovskite interface were reduced, and the carrier transport capability was improved. PSC based on MEA modification showed an enhanced PCE of 15.73%, compared to 12.66% without MEA treatment, and a fill factor (FF) of 68.30% on a 0.25 cm2 active area. Furthermore, the MEA-passivated device exhibits excellent stability and retains ~ 77% of its initial PCE after 1000 h under ambient storage without encapsulation. Thus, interface engineering based on the mono-ethanolamine passivation provides a feasible and novel strategy to improve the quality of ETL to fabricate high-efficiency planar PSCs. [ABSTRACT FROM AUTHOR]

This paper presents a detailed study of double perovskite (FA)2BiCuI6 based perovskite solar cells(PSC) using different kesterites as hole transport layers (HTL) and titanium-based electron transport layers (ETL). The designed double perovskite PSC utilized TiO2 as an ETL, different kesterite materials (CZTSe, CFTS, CBTS, CMTS, CNTS and CZTS) as the HTL, double perovskite material (FA)2BiCuI6 as the perovskite absorption layer (PAL), Indium tin oxide (ITO) as top electrode and Au as an anode. The different parameters of architecture (ITO/TiO2/(FA)2BiCuI6/HTL/Au) is improved via the SCAPS-1D simulator by first optimizing thickness and then the defect density of PAL. Energy band matching of the different layers with (FA)2BiCuI6 is thoroughly investigated in order to understand its operation. AM 1.5G illumination is used as input light source. To obtain optimum performance of (FA)2BiCuI6 based PSC the effects of optical thickness, defect density, temperature, series resistance, and shunt resistance are monitored. Among all the kesterites, CNTS based PSC performed extraordinarily well with PCE of 26.09 %. JSC 22.64 mA/cm2, VOC 1.38 V, FF 83.33 %, and the variables influencing solar cell performance are clarified by simulations. The findings presented in this work will aid researchers in the production of ecofriendly solar cells with great efficiency.

Perovskite solar cells (PSCs) have garnered significant attention in the photovoltaic field owing to their exceptional photoelectric properties, including high light absorption, extensive carrier diffusion distance, and an adjustable band gap. Temperature is a crucial factor influencing both the preparation and performance of perovskite solar cells. The annealing temperature exerts a pronounced impact on the device structure, while the operational temperature influences carrier transport, perovskite band gap, and interface properties. This paper provides a comprehensive review of the influence of varied annealing temperatures on the hole transport layer, electron transport layer, and perovskite layer. Additionally, we present an overview of innovative annealing methods applied to perovskite materials. The effects of diverse working temperatures on the overall performance of perovskite cells are thoroughly examined and discussed in this review. In the end, different temperature conditions under ISOS testing conditions are summarized.

Perovskite Solar Cells (PSCs) have managed to significantly capture attention by achieving efficiency values of 25.6% in a remarkably short period of around ten years. Each layer within the device plays a crucial role in the overall device efficiency when it comes to PSC production. PC61BM, a derivative of fullerene, is one of the most commonly used electron-transport layers (ETLs) in inverted-type PSCs. In this study, the improvement of the ETL was aimed by incorporating C60 into PC61BM, and the effects of the doped ETL on MAPbI3-based inverted-type PSCs were investigated. For inverted type PSCs which are fabricated under high humidity (40-60%) and room conditions (~25 °C), the power conversion efficiencies (PCEs) have boosted from 11.54% (for undoped PC61BM) to 13.40% (for C60-doped PC61BM). To comprehend the sources of improvement in the fabricated devices, a series of characterizations were carried out, including Current Density-Voltage (J-V), Hysteresis Factor (HF), Scanning Electron Microscope (SEM), and Atomic Force Microscope (AFM) measurements.

We developed inverted red quantum dot light-emitting diodes (QLEDs) with ZnO nanoparticles synthesized in open and closed systems. Wurtzite-structured ZnO nanoparticles were synthesized using potassium hydroxide and zinc acetate dihydrate at various temperatures in the open and closed systems. The particle size increases with increasing synthesis temperature. The ZnO nanoparticles synthesized at 50, 60, and 70 °C in the closed system have an average particle size of 3.2, 4.0, and 5.4 nm, respectively. The particle size is larger in the open system compared to the closed system as the methanol solvent evaporates during the synthesis process. The surface defect-induced emission in ZnO nanoparticles shifts to a longer wavelength and the emission intensity decreases as the synthesis temperature increases. The inverted red QLEDs were fabricated with a synthesized ZnO nanoparticle electron transport layer. The driving voltage of the inverted QLEDs decreases as the synthesis temperature increases. The current efficiency is higher in the inverted red QLEDs with the ZnO nanoparticles synthesized in the closed system compared to the devices with the nanoparticles synthesized in the open system. The device with the ZnO nanoparticles synthesized at 60 °C in the closed system exhibits the maximum current efficiency of 5.8 cd/A.

This work includes the numerical modeling (NM) of solar cells consisting of the active layer of CH3NH3SnI3 and electron transport layer of CdS, by employing a software SCAPS-1D. Organic-inorganic lead-based perovskites are superior in terms of power conversion efficiency. However, there are some serious drawbacks associated with them including poor stability, shorter life time and toxicity. Therefore, it is the demand of the hour to explore alternative materials to overcome these shortcomings. In this regard, tin is a competitive alternative to lead because it has similar electronic and chemical properties. Moreover, it is nontoxic, making it environmentally friendly. However, Sn based perovskite devices are reported with inferior power conversion efficacy, to date. In the present work, we have worked on a novel architecture of solar cells containing CH3NH3SnI3 as a light absorber layer and CdS as electron fetching layer. Optimization of the device was performed numerically by varying physical parameters related to the active layer such as thickness, defect density and shallow acceptor concentration. The proposed architecture of solar cells was proved as an efficient system with Jsc of 33.40 mA/cm2, Voc of 0.878 V, FF of 85.25 %, and PCE of 25.02 %. The temperature analysis has revealed that, temperature higher than 300 K increases the reverse saturation current, seriously degrading the structure of the device, hence limiting the power conversion performance of the solar cell. Furthermore, a rear electrode made of the high work function materials like Pt forms an ohmic junction at the HTL/anode interface, enhancing the performance of the device. Results of this study have paved the way for experimentalists to explore opportunities, to rationalize this architecture for real time applications such as inhouse lighting and laptop/smartphone charging.

A small molecular phenanthroline derivative Phen‐NaDPO (3‐[6‐(diphenylphosphinyl)‐2‐naphthalenyl]‐1,10‐Phenanthroline) to modify tin oxide (SnO2) electron‐transport layer (ETL) in organic solar cells is employed. Quantum chemistry calculations and experimental results show that Phen‐NaDPO can interact with SnO2, thereby effectively passivating the surface defects, reducing the work function and improving the electrical conductivity of SnO2, leading to more efficient electron extraction and transport in the organic solar cells (OSCs). Moreover, upon the Phen‐NaDPO modification, the decreased surface energy of SnO2 ETL accounts for enhanced exciton dissociation and charge transport, due to the more ordered molecular organizations of the active layers. Consequently, the inverted OSCs involving Phen‐NaDPO/SnO2 ETLs exhibit an enhanced power conversion efficiency of 17.06% (PM6:Y6) and 18.31% (PM6:L8‐BO), which is the highest efficiency for SnO2 ETL‐based binary solar cells to date. Furthermore, the devices based on Phen‐NaDPO/SnO2 ETL show better device stability (storage stability, photostability and humid stability), with T80 exceeding 200 h encapsulated under light irradiation and 400 h without encapsulation in high‐humidity ambient condition. These results demonstrate that the modification of SnO2 using wide‐band highly stable conjugated small molecules is very promising for simultaneously improve the efficiencies and device stability of OSCs. [ABSTRACT FROM AUTHOR]

Infrared (IR) solar cells are potential optoelectronic devices for boosting the power conversion efficiency (PCE) of conventional photovoltaics (such as pervoskite and silicon solar cells) by broadening the utilization range of the sunlight spectrum to short‐wavelength infrared region. PbSe colloidal quantum dots (QDs) are one of the optimal candidates for IR solar cells because of their tunable bandgap in the IR region and flexible solution processibility. At present, the best PbSe QD IR photovoltaics generally adopt ZnO as an electron transport layer (ETL). However, the intrinsic drawbacks and surface defects of ZnO can potentially deteriorate the PCE of devices. Herein, Ti3C2Tx, a representative 2D transition carbide, is combined with sol‐gel ZnO to develop a new hybrid ETL for fabricating high‐performance IR solar cells. This combination effectively suppresses the defects within ZnO by forming new bondings and simultaneously enhances the crystalline of ZnO film. Meanwhile, the introduction of Ti3C2Tx into ZnO film accelerates the transport and collection of photo‐generated carriers by constructing a new electron transport pathway. Consequently, compared to the bare devices, the infrared PCE of PbSe QD solar cells increases by 19.5% to 1.04%. These results demonstrate that this hybrid ETL can offer a bright approach for developing high‐performance optoelectronic devices. [ABSTRACT FROM AUTHOR]

At present, most high-efficiency organic-inorganic halide perovskite (OIHP) solar cells are made of polycrystalline perovskite films, and the surface or grain boundaries of these polycrystalline films often contain a large number of defects. The defects in the OIHP film will lead to non-radiative recombination of photogenerated carriers and induce the decomposition of the OIHP material, resulting in a decrease in the power conversion efficiency (PCE) and stability of the device. In this review, the types of defects in perovskite solar cells and the effects of defects on the performance of perovskite solar cells (PSCs) were analyzed. The progress of passivation of interface defects between electrode and charge transport layer or between charge transport layer and perovskite layer to obtain higher efficiency and stability of perovskite solar cells is introduced in detail. The design ideas of passivation molecules and the challenges facing the commercial application of perovskite photovoltaics are prospected. [ABSTRACT FROM AUTHOR]

The toxicity and stability concerns of lead based perovskite solar cells have limited the commercialization. The lead-free Cesium based double perovskite could be a viable answer to these issues. In this present work a theoretical analysis of Cesium based double perovskite solar cell using Spiro-OMeTAD as hole transport layer and effect of different ETLs such as SnO2, ZnO-NR, TiO2 and CdS has been studied. The optimized active layer thickness of 0.3 μm has been used and a device structure of FTO/ETLs/Cs2AgBiBr6/Spiro-OMeTAD/Cu was simulated. The Solar Cell Capacitance Simulator (SCAPS-1D) was used for one dimensional simulation and analysis. The maximum PCE of 5.62 % was found using SnO2 as ETL. The device performance has been optimized by employing various ETLs and the most suitable ETL for this structure was found to be SnO2. The maximum quantum efficiency of 86.09 % has been found for SnO2 electron transport layer. The simulation results obtained in this study are encouraging and will provide insightful guidance in replacing toxic Pb-based perovskite with eco-friendly inorganic perovskite solar cell. [ABSTRACT FROM AUTHOR]