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A pristine electron transport layer (ETL) usually delivers relatively low device performance due to high defect density and/or poor contact. Interface modification has been demonstrated to be one o...

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.

The mesoscopic electron transport layer (m-ETL) has been demonstrated to help perovskite solar cells (PSCs) construct a tough interface against stress and a good contact for efficient extraction of...

In recent years, the perovskite solar cells have gained much attention because of their ever-increasing power conversion efficiency (PCE), simple solution fabrication process, flyable, light-weight wearable and deployable for ultra-lightweight space and low-cost materials constituents etc. Over the last few years, the efficiency of perovskite solar cells has surpassed 25% due to high-quality perovskite-film accomplished through low-temperature synthesis techniques along with developing suitable interface and electrode-materials. Besides, the stability of perovskite solar cells has attracted much well-deserved attention. In this article we have focused on recent progress of the perovskite solar cells regarding their crystallinity, morphology and synthesis techniques. Also, demonstrated different layers such as electron transport-layers (ETLs), hole transport-layers (HTLs) and buffer-layers utilized in perovskite solar-cells, considering their band gap, carrier mobility, transmittance etc. Outlook of various tin (Sn), carbon and polymer-based perovskite solar cells and their potential of commercialization feasibility has also been discussed.

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.

In this study, we report the self-nanostructured growth of 4,6-bis(3,5-di(pyridin-3-yl)phenyl)-2-methylpyrimidine (B3PyMPM), which is widely used as an electron transport layer for organic light-emitting diodes (OLEDs). B3PyMPM nanostructures were formed on the surface of a substrate using vacuum thermal evaporation, and parameters such as substrate rotation speed and evaporation angle were altered to study their effect on the growth of nanostructures. Moreover, it was proven that the growth of nanostructures was dependent on the underneath materials. This self-nanostructured growth of B3PyMPM would affect the outcoupling and the efficiency improvement of OLEDs.

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.

Suitable electron transport materials bearing good interfacial contact, improved electron transport ability, and matched energy levels are indispensable for developing efficient perovskite solar cells (PSCs). Herein, regular (n‐i‐p) planar Cs0.05FA0.83MA0.12PbI2.55Br0.45 (CsFAMA) PSC devices were fabricated using a pyridine‐functionalized fullerene derivative (C60‐3‐BPy) as an independent electron transport layer (ETL), delivering a decent power conversion efficiency (PCE) of 18.22%, which is dramatically higher than that of the control device based on [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) ETL (15.70%). The energy level offset between C60‐3‐BPy and the perovskite is smaller than that based on PCBM ETL, which is beneficial for efficient ohmic contact in ETL/perovskite interface and improved open‐circuit voltage (Voc). Moreover, C60‐3‐BPy affords strong coordination interactions with perovskite, leading to an improved film quality of the perovskite layer with enlarged grain size and decreased trap state density, which contribute to facilitated electron extraction as reflected by the increases of both the fill factor (FF) and the short‐circuit current (Jsc). C60‐3‐BPy‐facilitated electron extraction further results in hysteresis‐free devices.

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.

As an effective electron transport layer, tin oxide (SnO2) has attracted much attention owing to its charge mobility and chemical stability, but it still suffers from high trap at the SnO2/perovski...

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.

The past few years have witnessed the rapid development of all-inorganic perovskite solar cells (PSCs). The interface of the electron transport layer (ETL)/perovskite is the vital charge separation...

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

Perovskite solar cells (PSCs) are a promising area of research among different new generations of photovoltaic technologies. Their manufacturing costs make them appealing in the PV industry compared to their alternatives. Although PSCs offer high efficiency in thin layers, they are still in the development phase. Hence, optimizing the thickness of each of their layers is a challenging research area. In this paper, we investigate the effect of the thickness of each layer on the photoelectric parameters of n-ZnO/p-CH3NH3PbI3/p-NiOx solar cell through various simulations. Using the Sol–Gel method, PSC structure can be formed in different thicknesses. Our aim is to identify a functional connection between those thicknesses and the optimum open-circuit voltage and short-circuit current. Simulation results show that the maximum efficiency is obtained using a perovskite layer thickness of 200 nm, an electronic transport layer (ETL) thickness of 60 nm, and a hole transport layer (HTL) thickness of 20 nm. Furthermore, the output power, fill factor, open-circuit voltage, and short-circuit current of this structure are 18.9 mW/cm2, 76.94%, 1.188 V, and 20.677 mA/cm2, respectively. The maximum open-circuit voltage achieved by a solar cell with perovskite, ETL and HTL layer thicknesses of (200 nm, 60 nm, and 60 nm) is 1.2 V. On the other hand, solar cells with the following thicknesses, 800 nm, 80 nm, and 40 nm, and 600 nm, 80 nm, and 80 nm, achieved a maximum short-circuit current density of 21.46 mA/cm2 and a fill factor of 83.35%. As a result, the maximum value of each of the photoelectric parameters is found in structures of different thicknesses. These encouraging results are another step further in the design and manufacturing journey of PSCs as a promising alternative to silicon PV.

Interests in minimalist device structure design of perovskite solar cells (PSCs) have accelerated the rapid advances of electron transport layer-free PSCs by composition and solvent engineering. Fo...

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.

Fully inorganic black orthorhombic (B-γ) CsSnI3 has become a promising candidate for perovskite solar cell (PSC) thanks to its low toxicity and decently high theoretical power conversion efficiency (PCE). However, so far, the reported PCE of the B-γ CsSnI3 PSC is still not comparable with its lead-based or organotin-based counterparts. Herein, a mixed electron transport layer (ETL) composed of ZnO nanoparticles (NPs) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) is incorporated into inverted B-γ CsSnI3 PSCs. The mixed ETL exhibits the merits of both ZnO and PCBM. The highest PCE of 6.08% was recorded for the PSC with mixed ZnO-PCBM ETL, which is 34.2% higher than that of the device with plain PCBM ETL (PCE of 4.53%) and 28.8% superior to that of plain ZnO ETL-based device (PCE of 4.72%). Meanwhile, the mixed ZnO-PCBM ETL-based PSC retained 71% of its initial PCE under inert conditions at room temperature after 60 days of storage and maintained 67% PCE after 20 days of storage under ambient air at 30% relative humidity and room temperature.

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/...

Interface engineering is a powerful tool to improve the performance of polymer solar cells (PSCs), and zinc oxide (ZnO) is a significant interfacial material for PSCs. However, ZnO is easy to agglo...

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.

Vertically aligned ZnO nanorods were grown using the chemical deposition method. The presence of various ZnO seed layers in the growth process was examined. Perovskite cells, with these films, were...

We characterized the prominent electron transport layer 2,2′,2"-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) via single crystal X-ray diffraction, grazing incidence X-ray diffractio...

Among deposition methods, ultrasonic spray-coating has particularly strong potential for large-scale production due to its low cost and capability to produce thin films with large-scale areas for i...