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We developed highly efficient quantum dot light-emitting devices (QD-LEDs) by improving the charge balance with triple hole injection and transport layers consisted of MoO3/poly[N,N′-bis(4-butylphe...

We report a highly efficient quantum dot light emitting diode (QLEDs) with a radio frequency (RF) sputtered ZnO thin film as an electron transport layer (ETL) instead of the conventional ZnO nanoparticles (NPs) by solution process. ZnO NPs have been used as a key material to improve the performance of QLEDs, but the charge imbalance in ZnO NPs resulting from fast electron injection, and their limited uniformity are significant disadvantages. In this study, ZnO layers were deposited by RF sputtering with various O2 partial pressures. All of the ZnO films showed preferential growth along the (002) direction, smooth morphology, and good optical transmittance. To test their feasibility for QLEDs, we fabricated devices with RF sputtered ZnO layers as an ETL, which has the inverted structure of ITO/RF sputtered ZnO/QDs/CBP/MoO3/Al. The optical/electrical characteristics of two devices, comprised of RF sputtered ZnO and ZnO NPs, were compared with each other. QLEDs with the sputtered ZnO ETL achieved a current efficiency of 11.32 cd/A, which was higher than the 8.23 cd/A of the QLEDs with ZnO NPs ETL. Next, to find the optimum ZnO thin film for highly efficient QLEDs, deposition conditions with various O2 partial pressures were tested, and device performance was investigated. The maximum current efficiency was 13.33 cd/A when the ratio of Ar/O2 was 4:3. Additional oxygen gas reduced the O vacancies in the ZnO thin film, which resulted in a decrease in electrical conductivity, thereby improving charge balance in the emission layer of the QLEDs. As a result, we provide a way to control the ZnO ETL properties and to improve device performance by controlling O2 partial pressure.

Perovskite solar cells have become a hot topic in the solar energy device area due to high efficiency and low cost photovoltaic technology. However, their function is limited by expensive hole transport material (HTM) and high temperature process electron transport material (ETM) layer is common device structure. Numerical simulation is a crucial technique in deeply understanding the operational mechanisms of solar cells and structure optimization for different devices. In this paper, device modelling for different perovskite solar cell has been performed for different ETM layer, namely: TiO2, ZnO, SnO2, PCBM (phenyl-C61-butyric acid methyl ester), CdZnS, C60, IGZO (indium gallium zinc oxide), WS2 and CdS and effect of band gap upon the power conversion efficiency of device as well as effect of absorber thickness have been examined. The SCAPS 1D (Solar Cell Capacitance Simulator) has been a tool used for numerical simulation of these devices.

We report highly efficient and robust quantum dot light-emitting diodes (QLEDs) with Li-doped TiO2 nanoparticles (NPs) as an electron transport layer (ETL). As core materials, ZnO-based inorganic NPs can enhance the performance of QLEDs due to their suitable energy level and solution processability. However, their fast electron mobility and instability in organic solvents are two main obstacles to practical display applications. The colloidal stability of TiO2 NPs in ethanol was confirmed after three day-storage, while ZnO NPs showed severe agglomeration. Inverted structure QLEDs using 3% Li-doped TiO2 NP were successfully fabricated and their optical/electrical properties were investigated. With 3% Li-doped TiO2 NPs, the charge balance in the emitting layer of the QLEDs was improved, which resulted in a maximum luminance of 159,840 cd/m2 and external quantum efficiency (EQE) of 9.12%. These results were comparable to the performance of QLEDs with commonly used ZnO NPs. Moreover, the QLEDs with the Li-doped TiO2 NPs showed more stable characteristics than those with ZnO NPs after 7 days in ambient conditions. The EQE of the QLEDs with Li-doped TiO2 NPs was reduced by only 4.9%. These results indicate that Li-doped TiO2 NPs show great promise for use as a solution based inorganic ETL for QLEDs.

The adequate control of dark current is the key to achieving high detectivity in organic photodetectors (OPDs). In this study, we incorporated hafnium (Hf), a rare earth mineral, into tin oxide (SnO2) to form hafnium doped SnO2 (Hf-SnO2) as an electron transport layer (ETL) in OPDs. It was observed that the performance of OPDs with a Hf-SnO2 electron transport layer in OPDs is superior to that of conventional SnO2 as it significantly reduces the leakage current recording a high specific detectivity of 8.70 × 1011 Jones and a bandwidth of 229.63 kHz at −1 V and 525 nm. Furthermore, Hf-SnO2 can be processed at a low temperature, thereby broadening the fields of applications such as flexible devices and large area cells.

Achieving long‐term device stability is one of the most challenging issues that impede the commercialization of perovskite solar cells (PSCs). Recent studies have emphasized the significant role of the cathode interfacial layer (CIL) in determining the stability of inverted p‐i‐n PSCs. However, experimental investigations focusing on the influence of the CIL on PSC degradation have not been systematically carried out to date. In this study, a comparative analysis was performed on the PSC device stability by using four different CILs including practical oxides like ZnO and TiOx. A new implemented co‐doping approach was found to results in high device performance and enhanced device stability. The PSC with a thick film configuration of chemically modified TiOx CIL preserves over 77 % of its initial efficiencies of 17.24 % for 300 h under operational conditions without any encapsulation. The PSCs developed are among the most stable reported for methylammonium lead iodide (MAPbI3) perovskite compositions., In for the CIL: Highly stable inverted perovskite solar cells (PSCs) are assembled by using chemically modified titanium suboxide (TiOx) as the cathode interfacial layer (CIL). Codoping enhances the electrical properties of the TiOx CIL, providing better inner encapsulation with thick film configuration. The PSCs exhibit significantly improved operational stability, maintaining >77 % of their initial efficiencies for up to 300 h without encapsulation.

Carbon-based perovskite solar cells are competitive candidate for photovoltaic applications in future due to their high-performance, low-cost and good stability. However, the hole transport materials are limited and their properties are not satisfying in carbon-based perovskite solar cells. Here, we report a typical p-type P3HT as hole transport layer for all low-temperature processed carbon-based perovskite solar cells with ZnO electron transport layer. Because P3HT has energy level matching with perovskite film and can facilitate the hole collection process, the power conversion efficiency of device can reach 16.05% that far higher than devices without P3HT hole transport layer. More importantly, due to good hydrophobicity and encapsulation function of P3HT, the stability of devices can also be significantly improved. The power conversion efficiency of device is able to retain over 90% of their initial value over 1200 h upon ambient air exposure without encapsulation. This present study provides a simple strategy for fabricating low-cost, highly efficient and stable perovskite solar cells.

The electron transport layer (ETL) plays an important role as a buffer layer in the efficient n-i-p planar heterojunction perovskite solar cells (PSCs). Recently, a new ETL, (CH3)2Sn(COOH)2 (CSCO),...

Despite demonstrating remarkable power conversion efficiencies (PCEs), perovskite solar cells (PSCs) have not yet achieved their full potential. In particular, the interfaces between the perovskite and charge transport layers account for the vast majority of the recombination losses. Interfacial contact and band alignment between the low-temperature-processed TiO2 electron transport layer (ETL) and the perovskite are essential to minimize nonradiative recombination losses. In this study, a CeOx interlayer is employed to modify the perovskite/TiO2 interface, and the charge transport properties of the devices are investigated. The bilayer-structured TiO2/CeOx ETL leads to the modification of the interface energetics, resulting in improved electron extraction and reduced nonradiative recombination in the PSCs. Devices based on TiO2/CeOx ETL exhibit a high open-circuit voltage (Voc) of 1.13 V and an enhanced PCE of more than 20% as compared with Voc of 1.08 V and a PCE of approximately 18% for TiO2-based devices. Moreover, PSCs based on TiO2/CeOx ETL maintain over 88% of their initial PCEs after light illumination for 300 min, whereas PSCs based on TiO2 ETL almost failed. This study provides an efficient strategy to enhance the PCE and stability of PSCs based on a low-temperature-processed TiO2 ETL.

SnO2 has been the most commonly used electron transport layer (ETL) in perovskite solar cells (PSCs) due to its excellent electron mobility and stability. To meet the applications of SnO2 ETL in la...

Abstract As a promising photovoltaic technology, perovskite solar cells (pero-SCs) have developed rapidly over the past few years and the highest power conversion efficiency is beyond 25%. Nowadays, the planar structure is universally popular in pero-SCs due to the simple processing technology and low-temperature preparation. Electron transport layer (ETL) is verified to play a vital role in the device performance of planar pero-SCs. Particularly, the metal oxide (MO) ETL with low-cost, superb versatility, and excellent optoelectronic properties has been widely studied. This review mainly focuses on recent developments in the use of low-temperature-processed MO ETLs for planar pero-SCs. The optical and electronic properties of widely used MO materials of TiO2, ZnO, and SnO2, as well as the optimizations of these MO ETLs are briefly introduced. The commonly used methods for depositing MO ETLs are also discussed. Then, the applications of different MO ETLs on pero-SCs are reviewed. Finally, the challenge and future research of MO-based ETLs toward practical application of efficient planar pero-SCs are proposed. Graphical abstract

Highlights This review summarizes applications and developments of MXenes in solar cells by far. The issues needing to be addressed for performance improvement of the related solar cells are discussed.Suggestions are given for pushing exploration of MXenes’ application in solar cells., Application of two-dimensional MXene materials in photovoltaics has attracted increasing attention since the first report in 2018 due to their metallic electrical conductivity, high carrier mobility, excellent transparency, tunable work function and superior mechanical property. In this review, all developments and applications of the Ti3C2Tx MXene (here, it is noteworthy that there are still no reports on other MXenes’ application in photovoltaics by far) as additive, electrode and hole/electron transport layer in solar cells are detailedly summarized, and meanwhile, the problems existing in the related studies are also discussed. In view of these problems, some suggestions are given for pushing exploration of the MXenes’ application in solar cells. It is believed that this review can provide a comprehensive and deep understanding into the research status and, moreover, helps widen a new situation for the study of MXenes in photovoltaics.

We report high-efficiency quantum dot light-emitting diodes (QLEDs) with Li-doped TiO2 nanoparticles (NPs) as an alternative electron transport layer (ETL). Colloidally stable TiO2 NPs are applied as ETLs of inverted structured QLEDs and the effect of the addition of lithium (Li) to TiO2 NPs on device characteristics is studied in detail. Compared to pristine TiO2 NPs, Li-doped ones are found to be beneficial for the charge balance in the emitting layer of QLEDs mainly by means of their upshifted conduction band minimum, which in turn limits electron injection. A green QLED with 5% Li-doped TiO2 NPs produces a maximum luminance of 169 790 cd m−2, an EQE of 10.27%, and a current efficiency of 40.97 cd A−1, which indicate the best device performances to date among QLEDs with non-ZnO inorganic ETLs. These results indicate that Li-doped TiO2 NPs show great promise for use as a solution-based inorganic ETL for future QLEDs.

The development of perovskite solar cells (PSCs) as an efficient and cost-effective alternative to traditional approaches to solar energy transduction has received much recent attention, and there has been considerable progress made with reported power conversion efficiencies now surpassing 25%. This development is encouraging and is a result of intensive research on device design, factors affecting long-term stability of PSCs, and systematic material development in which electron transport layer (ETL) materials play a crucial role to afford high-performance PSC devices. ETL materials, including (6-(1,10-phenanthrolin-3-yl)naphthalen-2-yl)diphenylphosphine oxide (Phen-NaDPO), and n-type materials based on the naphthalene diimide (NDI) structure, appear to be amongst the most promising materials to date. This article provides an up-to-date review on organic n-type ETL materials, both polymeric and small molecules, based on NDI format, detailing reports of structures with key relevant parameters, such as the efficiency and stability of PSCs. The review is written from a perspective of organic chemistry and we believe this will provide fundamental advice on the future design of new ETL materials based on NDIs that will afford more efficient and stable PSCs.

UV induced decomposition of perovskite material is one of the main factors to severely destroy perovskite solar cells for instability. Here we report a UV stable perovskite solar cell with an Fe2O3 electron transport layer (ETL) made by spin-coating water dispersed Fe3O4 nanoparticles. Devices with Fe2O3 ETLs prepared from 10 nm Fe3O4 nanoparticles show nearly no decrease of photoelectric conversion efficiency (PCE) upon continuous exposure to very high UV light irradiation (300 W Xe lamp) for 10 hours in contrast to the TiO2 ETL based samples with more than 30% reduction of PCE, and their PCE (14.33) is also much superior to those of devices with Fe2O3 ETLs made conventionally from FeCl3 solution (7.7%). Through the study of Fe2O3 thin film prepared perovskite solar cells, it is found that compact, high transmittance, low leakage and low transmission impedance devices can be obtained by using an appropriate size of Fe3O4 nanoparticles. Our major findings are expected to provide a guide to design UV-protected compact electron transport layers for UV-stable perovskite solar cells.

The experimental search for high-efficiency perovskite solar cells (PSCs) is an extremely challenging task due to the vast search space comprising the materials, device structures, and preparation methods. Herein, using a two-step machine learning approach and 2006 PSC experimental data points extracted from 880 articles published between 2013 to 2020, we develop some heuristics for high-efficiency PSC and power conversion efficiency (PCE) improvement induced by doping of the electron transport layer (ETL). We show that the utilizations of SnO2 and TiO2 ETLs, mixed-cation perovskites, dimethyl sulfoxide and dimethylformamide perovskite precursor solvents and anti-solvent treatment are the most significant factors that lead to the high PCEs of PSCs. The PCE can be further improved by ETL doping for tuning the conduction band minimum, Fermi level, and conductivity of the ETL. Moreover, we predict that a FA–MA based PSC with a Cs-doped TiO2 ETL and a Cs–FA–MA based PSC with S-doped SnO2 ETL exhibit PCEs of as high as 30.47% and 28.54%, respectively. This study provides insightful guidance for the development of high-efficiency PSCs.

Solution processed metal oxides with the characteristics of low cost, high mobility and good transparency are promising materials for the carrier transport layer of optoelectronic devices. So far, solar cells with tin oxide (SnO2) transport layers have been demonstrated to achieve high efficiency and long-term stability. However, it is still a challenge to achieve highly efficient and long-term stable quantum dot light-emitting devices (QLEDs) with SnO2. Here, we prepared QLEDs with a low-temperature SnO2 electron transport layer (ETL), and found that the residual hydroxyl group (–OH) seriously degenerates the operating lifetime of the QLEDs. UV-Ozone treatment (UVO) is then proposed to decompose the residual tin hydroxide into stoichiometric SnO2. Compared with the control QLEDs with SnO2 without UVO, the QLEDs with UVO SnO2 possess the same efficiency, but show a nearly two times higher operating lifetime. With an initial luminance of 500 cd m−2, the QLEDs with UVO SnO2 show a half-luminance operating time of 2168 h, while that of the control device is only 1015 h.

The industrialization of perovskite solar cells (PSCs) is based on the development of efficiency and stability. Here, a composite film of a polyethylenimine ethoxylated (PEIE) and tellurophene-based two-dimensional metal–organic framework (2D MOF) was introduced to realize the nondestructive passivation of TiO2. This interfacial layer can not only realize the effective passivation of TiO2, but can also further improve the morphology of the perovskite film. After the modification of the PEIE-2D MOF composite film, the morphology and crystallinity of the perovskite film are greatly optimized, the trap states in the TiO2 layer are reduced, and the electron transport in the device is enhanced, thus finally achieving highly efficient and stable FA0.25MA0.75PbI3 PSCs with a maximum efficiency of 22.22%. It was demonstrated that the reduced trap states and the smooth surface of the TiO2 electron transport layer are the reasons for the high performance of modified PSCs. This method provides a new way for improving the interface state to achieve highly efficient and stable PSCs.

Improved device performance of perovskite light-emitting diodes (LEDs) is demonstrated through the synergistic effect of the optimized CsPbI3 nanocrystals (NCs) as the emissive layer (EML) and ZnO/...

The study focuses on optoelectronic model of perovskite solar cell using finite element method to optimize the thickness of electron transport and absorber layers implemented using COMSOL multi-physics modeling. The analyzed perovskite solar cell shows a power conversion efficiency of 17.95% for an optimum film thickness of TiO2 (90 nm)/CH3NH3PbI3 (100 nm)/Spiro-OMeTAD (300 nm). The obtained simulated results were examined to improve the efficiency of the device and also to understand the impact of factors affecting the performance of the solar cell. Furthermore, the working potential of perovskite solar cell was explored to demonstrate the impending scope of stepwise progress in the novel technology.

In this article, the numerical investigations on a novel (ITO/CeO2/SnS/NiO/Mo) heterostructure of the SnS-based solar cell have been presented using SCAPS-1D simulation software. The main objective of the study was the exploration of the effect of NiO hole transport layer (HTL) on the performance of the proposed SnS-based heterojunction solar cell. The open circuit voltage of the proposed cell has been enhanced up to 345 mV after using NiO HTL which indicates a significant reduction of surface recombination velocity at SnS/electrode interface. Around 12.78% efficiency enhancement was observed after using NiO HTL in the SnS-based heterojunction solar cell, and an efficiency of 25.1% could be obtained from the proposed heterojunction solar cell. It was found that the cell performance depended on the carrier concentration and thickness of the CeO2 electron transport layer (ETL), SnS absorber layer, and NiO HTL, respectively. The effects of deep level defect density of the SnS absorber layer and interface defect density of NiO/SnS and CeO2/SnS on the cell performance ware also studied. These findings reveal that the NiO could be a promising HTL for the fabrication of low cost, high-efficiency SnS-based heterojunction solar cell.

Electron transport layer (ETL) plays an important role in improving the performance and stability of perovskite solar cells (PSCs). SnO2 is a good semiconductor material with high electromigration and wide band gap. TiO2 has the advantages of superior position of conducting band (CB), long electronic life and low preparation cost, so SnO2 and TiO2 are often used in ETL of PSCs. In this paper, the preparation progress of SnO2, TiO2 and SnO2/TiO2 composite ETL is reviewed.

Recently, organic–inorganic hybrid metal halide perovskite (O-IHMHP) has been diffusely used in solar cells due to its remarkable photoelectric property and inexpensive film-forming process. Since organic–inorganic hybrid metal halide perovskite solar cells (O-IHMHPSCs) were introduced in 2009, their photoelectric conversion efficiency has been increased to 25.2%, and their lifespan has been extended to tens of thousands of hours. However, due to processing factors, defects consist in the interfaces of O-IHMHP with the electron transport layer and the hole transport layer. To improve the stability and property of O-IHMHPSCs, these defects must be addressed; to do so, passivation is commonly applied at the interface. This work reviews research on the interface passivation of O-IHMHPSCs. Here, the passivation mechanisms of different additives on the interface defects of O-IHMHP films are analyzed, their impacts on the stability and property of O-IHMHPSCs are compared, and their roles in O-IHMHPSCs are summarized. Finally, the research and development trends of the defect passivation of O-IHMHPSCs are discussed.

In the past few years, the power conversion efficiencies (PCEs) of perovskite solar cells (PSCs) have increased from 3.81 to 25.2%, surpassing those of all almost all thin films solar cells. For hi...

In recent years, perovskite material has been extensively studied due to its unique physical properties and promising application in the third generation of solar cells. In particular, Sn-based perovskite has been considered to replace Pb-based perovskite because of the toxic effects and it can lead to other serious problems related to the environment. Cs2SnI6 perovskite has been known to be synthesized in a simple chemical process and it can be produced on a large scale. Moreover, this material is also oxygen and moisture stable due to the high oxidation state of tin. In this study, we synthesize air-stable Cs2SnI6 perovskite by the use of the wet chemical process at room temperature. Next, we attempt to fabricate the inverted bulk heterojunction solar cells incorporated Cs2SnI6 as electron transport layer in the configuration of ITO/ZnO/Cs2SnI6/P3HT:PCBM/PEDOT:PSS/Ag to improve device performance. The Cs2SnI6 perovskite shows an Fm-3m space group with a cubic lattice parameter of 11.62Å confirmed by X-Ray Diffraction (XRD) measurement, while UV-Vis measurement indicates this type of perovskite has direct band gap ~3.1 eV. The fabricated solar cell device reveals the enhancement in current density at short circuit condition (Jsc) from 64.69 mA/cm2 to 77.02 mA/cm2 with the addition of 2.25 mg/ml Cs2SnI6 along with the enhancement of power conversion efficiency (PCE) from 7.05% to 9.75% as characterized by J-V measurement. In our case, the voltage at open circuit condition (Voc) of the device does not perform significant improvement. Besides, it is found that the solar cell devices are quite stable even after exposure in the air for six weeks after fabrication, as indicated by PCE performance.

Nickel oxide (NiOx) film is employed to replace PEDOT:PSS as the hole transport layer for the inverted perovskite solar cells (PSCs) with Zinc Oxide as electron transport layer, and we focus on the...

The realization of highly efficient devices depends on efficient charge carrier injection, employment of materials, and proper fabrication methodologies. However, it is difficult to manufacture hig...

The mismatch of the energy level between electron transport layer (ETL) and perovskite film (PS) is one of the origins of current-voltage (J-V) hysteresis in perovskite solar cells (PSCs). Drift-di...

Zinc oxide (ZnO) nanoparticles (NPs) are widely used as electron-transport layers in quantum dots (QDs) light-emitting diodes (QLEDs). In this work, we show that the size of the NPs can be tuned wi...

Organic-inorganic lead halide perovskites are promising materials for realization of low-cost and high-efficiency solar cells. Because of the toxicity of lead, Sn-based perovskite materials have been developed as alternatives to enable fabrication of Pb-free perovskite solar cells. However, the solar cell performance of Sn-based perovskite solar cells (Sn-PSCs) remains poor because of their large open-circuit voltage (

The use of LiF as a thin interlayer between the electron transport layer and cathode has played a pivotal role in remarkable advances in perovskite LEDs (PeLEDs); however, the mechanism behind the effect of LiF remains to be fully understood. Here, we report a combined experimental and computational study, from which we ascribe the benefits of a LiF interlayer to the migration of dissociated Li into the cathode and dissociated F into the anode. Electronic device simulations reveal that the former improves electron injection by lowering the Schottky barrier height, while the latter reduces the barrier width. These reduce turn-on voltage and improve current density and charge balance in LEDs. We fabricate PeLEDs with and without the LiF interlayer and link these materials and electronic phenomena to the device light-current-voltage characteristics. X-ray photoelectron spectroscopy obtained in sputter profiling of PeLEDs corroborates the dissociation of LiF.

Perovskite solar cells (PSCs) are among the most promising emerging photovoltaic technologies, demonstrating power conversion efficiencies (PCEs) close to 24%. The major challenge hampering commercialization of this technology is the low stability toward inevitable stress factors of PV modules such as temperature variations. Temperature variations are reported to induce a decline in photocurrent of up to 80%, depending on the device architecture, the charge transport layers, and the perovskite absorber material. The effect is particularly pronounced in methylammonium lead iodide-based PSCs, with TiO2 as the electron transport layer (ETL) and spiro-MeOTAD as the hole transport layer (HTL). This article reports on three different strategies to overcome the temperature-variation-induced degradation by altering the interfaces. The charge selective transport layers, the perovskite absorber layer composition, and the perovskite deposition technique are varied. We find that the interface between the ETL and the perovskite layer is the key to temperature-variation-induced degradation. We demonstrate stable PSCs with regard to temperature variations with PCEs as high as 19.5%. Finally, the relevance of the temperature-variation-induced degradation for outdoor applications is shown by stressing PSCs with real outdoor temperature profiles (between 21 and 75 °C).

Because of the wide emission spectrum tunability that ranges from the visible region to the near-infrared, InP-based colloidal quantum dots (QDs) show great promise for use in the next-generation f...

SnO2 has been proven to be an effective electron transport layer (ETL) material for perovskite solar cells (PSCs) owing to its excellent electrical and optical properties. Here, we introduce a viable spray coating method for the preparation of SnO2 films. Then, we employ a SnO2 film prepared using the spray coating method as an ETL for PSCs. The PSC based on the spray-coated SnO2 ETL achieves a power conversion efficiency of 17.78%, which is comparable to that of PSCs based on conventional spin-coated SnO2 films. The large-area SnO2 films prepared by spray coating exhibit good repeatability for device performance. This study shows that SnO2 films prepared by spray coating can be applied as ETLs for stable and high-efficiency PSCs. Because the proposed method involves low material consumption, it enables the low-cost and large-scale production of PSCs.

A robust electron transport layer (ETL) is an essential component in planar-heterojunction perovskite solar cells (PSCs). Herein, a sol-gel-driven ZrSnO4 thin film is synthesized and its optoelectronic properties are systematically investigated. The optimized processing conditions for sol-gel synthesis produce a ZrSnO4 thin film that exhibits high optical transmittance in the UV-Vis-NIR range, a suitable conduction band maximum, and good electrical conductivity, revealing its potential for application in the ETL of planar-heterojunction PSCs. Consequently, the ZrSnO4 ETL-based devices deliver promising power conversion efficiency (PCE) up to 19.05% from CH3NH3PbI3-based planar-heterojunction devices. Furthermore, the optimal ZrSnO4 ETL also contributes to decent long-term stability of the non-encapsulated device for 360 h in an ambient atmosphere (T~25 °C, RH~55%,), suggesting great potential of the sol-gel-driven ZrSnO4 thin film for a robust solution-processed ETL material in high-performance PSCs.

An ideal n-i-p perovskite solar cell employing a Pb free CH3NH3SnI3 absorber layer was suggested and modelled. A comparative study for different electron transport materials has been performed for three devices keeping CuO hole transport material (HTL) constant. SCAPS-1D numerical simulator is used to quantify the effects of amphoteric defect based on CH3NH3SnI3 absorber layer and the interface characteristics of both the electron transport layer (ETL) and hole transport layer (HTL). The study demonstrates that amphoteric defects in the absorber layer impact device performance significantly more than interface defects (IDL). The cell performed best at room temperature. Due to a reduction in Voc, PCE decreases with temperature. Defect tolerance limit for IL1 is 1013 cm−3, 1016 cm−3 and 1012 cm−3 for structures 1, 2 and 3 respectively. The defect tolerance limit for IL2 is 1014 cm−3. With the proposed device structure FTO/PCBM/CH3NH3SnI3/CuO shows the maximum efficiency of 25.45% (Voc = 0.97 V, Jsc = 35.19 mA/cm2, FF = 74.38%), for the structure FTO/TiO2/CH3NH3SnI3/CuO the best PCE is obtained 26.92% (Voc = 0.99 V, Jsc = 36.81 mA/cm2, FF = 73.80%) and device structure of FTO/WO3/CH3NH3SnI3/CuO gives the maximum efficiency 24.57% (Voc = 0.90 V, Jsc = 36.73 mA/cm2, FF = 74.93%) under optimum conditions. Compared to others, the FTO/TiO2/CH3NH3SnI3/CuO system provides better performance and better defect tolerance capacity.

Surface passivation, which has been intensively studied recently, is essential for the perovskite solar cells (PSCs), due to the intrinsic defects in perovskite crystal. A series of chemical or physical methods have been published for passivating the defects of perovskites, which effectively suppressed the charge recombination and enhanced the photovoltaic performance. In this study, the n-type semiconductor of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) is dissolved in chlorobenzene (CB) for the surface passivation during the spin-coating process for depositing the two-dimensional (2D) perovskite film. This approach simplifies the fabrication process of 2D PSCs and benefits the film quality. As a result, the defects of perovskite film are effectively passivated by this method. A better perovskite/PCBM heterojunction is generated, exhibiting an increased film coverage and improved film morphology of PCBM. It is found that this technology results in an improved electron transporting performance as well as suppressed charge recombination for electron transport layer. As a result, PSCs based on the one-step formed perovskite/PCBM heterojunctions exhibit the optimized power conversion efficiency of 15.69% which is about 37% higher than that of regular perovskite devices. The device environmental stability is also enhanced due to the quality improved electron transport layer.

Much effort has been directed at understanding organic light-emitting device (OLED) efficiency and the role of bimolecular quenching in efficiency roll-off. Quenching is less widely discussed at low-bias, where populations are reduced. Here, we describe lock-in-based photoluminescence measurements on working phosphorescent OLEDs to demonstrate that this assumption is not generally valid, and that significant exciton-polaron quenching is present even prior to turn-on. Exciton-polaron quenching arises with holes accumulated due to spontaneous orientation polarization in the electron transport layer. This low-bias quenching is found to strongly determine maximum achievable efficiency, suggesting a need to refine materials selection and device design rules.