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Tin dioxide (SnO2) has recently been recognized as an excellent electron transport layer (ETL) for perovskite solar cells (PSCs) due to its advantageous properties, such as its high electron mobility, suitable energy band alignment, simple low-temperature process, and good chemical stability. In this work, nitrogen-doped graphene quantum dots (N-GQDs) were prepared using a hydrothermal method and then used to fabricate N-GQD:SnO2 nanocomposite ultrathin films. N-GQD:SnO2 nanocomposite ultrathin films were investigated and applied as electron transport layers in planar PSCs. The presence of N-GQDs with an average size of 6.2 nm in the nanocomposite improved its morphology and reduced surface defects. The excitation–emission contour map indicated that the N-GQDs exhibited a remarkably enhanced light-harvesting capability due to the possibility of absorbing UV light and producing emissions in the visible range. The quenching of photoluminescence spectra showed that the N-GQDs in nanocomposite ultrathin films improved electron extraction and reduced charge recombination. As a result, the power conversion efficiency (PCE) of our planar PSCs fabricated with the optimized N-GQD:SnO2 nanocomposite electron transport layer was improved by 20.4% over pristine SnO2-based devices.

Compositional engineering is considered one of the recent interesting techniques used in the field of perovskite solar cells (PSCs). In this method, more than one material was used in a specific cation in the perovskite structure. This work aims to simulate the cesium-containing triple-cation perovskite (TCP) via the SCAPS-1D simulation program with a device structure of ITO/SnO2/TCP/Spiro-OMeTAD/Au. First, we studied the effect of interface defects on the PCSs with respect to experimental results and found that when no interface defects occur, the power conversion efficiency (PCE) reaches a value of 22.16% which is higher than the reported PCE, implying that the fabricated cell suffers from the interface defects as a main effect on cell degradation. Incorporating interface defects into the simulation results in a very good match between the experimental and simulated data with a PCE of 17.92%. Further, to provide possible routes to enhance the performance of the solar cell under investigation, impacts of absorber layer thickness, conduction band offset (CBO), surface recombination velocity, and light intensity were explored. In addition, hole transport layer (HTL)-free design was investigated to alleviate the instability issues associated to the organic HTL, leading to a PCE of 18.28%, for a surface velocity of 104 cm/s, which is interestingly higher than the initial cell. The provided study reveals the critical role of interface defects and other key design factors and suggests potential solutions to alleviate the subsequent degradation mechanisms, thereby enhancing the overall cell performance.

The electron transport layer (ETL) has been extensively investigated as one of the important components to construct high-performance perovskite solar cells (PSCs). Among them, inorganic semiconducting metal oxides such as titanium dioxide (TiO2), and tin oxide (SnO2) present great advantages in both fabrication and efficiency. However, the surface defects and uniformity are still concerns for high performance devices. Here, we demonstrated a bilayer ETL architecture PSC in which the ETL is composed of a chemical-bath-deposition-based TiO2 thin layer and a spin-coating-based SnO2 thin layer. Such a bilayer-structure ETL can not only produce a larger grain size of PSCs, but also provide a higher current density and a reduced hysteresis. Compared to the mono-ETL PCSs with a low efficiency of 16.16%, the bilayer ETL device features a higher efficiency of 17.64%, accomplished with an open-circuit voltage of 1.041 V, short-circuit current density of 22.58 mA/cm2, and a filling factor of 75.0%, respectively. These results highlight the unique potential of TiO2/SnO2 combined bilayer ETL architecture, paving a new way to fabricate high-performance and low-hysteresis PSCs.

Ternary complex oxides with cubic pyrochlore structure BixFeyWOq (BFWO) were obtained by hydrothermal synthesis at different pH values of hydrothermal fluid and were first used as electron transport layers in perovskite solar cells (PSCs). The analysis of photovoltaic parameters measured for BFWO-based PSCs demonstrated that BFWO materials obtained at pH 2 allow to improve the PSC performance by ~4% (rel.) in comparison with state-of-the-art PSCs. In addition, BFWO-based PSCs exhibited higher tolerance to the degradation under continuous illumination., В данной работе в качестве электронно-транспортных слоев в перовскитных солнечных элементах (ПСЭ) впервые были использованы тонкие пленки тройных сложных оксидов со структурой пирохлора вида BixFeyWOq (BFWO). Анализ фотоэлектрических параметров сконструированных ПСЭ показал, что эффективность образца с BFWO слоем на 4% выше, чем ПСЭ на основе стандартно используемого TiO2 слоя. Кроме того, ПСЭ с BFWO материалом демонстрировали повышенную устойчивость к непрерывному освещению.

Recently, the simulation of perovskite solar cells (PSCs) via SCAPS-1D has been widely reported. In this study, we adopted SCAPS-1D as a simulation tool for the numerical simulation of lead-free (Pb-free) PSCs. We used methyl ammonium germanium iodide (MAGeI3) as a light absorber, zinc oxysulphide (ZnOS) as an electron transport layer (ETL), and spiro-OMeTAD as a hole transport layer. Further, the thickness of the ZnOS, MAGeI3, and spiro-OMeTAD layers was optimized. The optimal thicknesses of the ZnOS, MAGeI3, and spiro-OMeTAD layers were found to be 100 nm, 550 nm, and 100 nm, respectively. The optimized MAGeI3-based PSCs exhibited excellent power conversion efficiency (PCE) of 21.62%, fill factor (FF) of 84.05%, and Jsc of 14.51 mA/cm2. A fantastic open circuit voltage of 1.77 V was also obtained using SCAPS-1D. We believe that these theoretically optimized parameters and conditions may help improve the experimental efficiency of MAGeI3-based PSCs in the future.

Perovskite (Pvk) solar cells and Pvk/silicon (Si) tandem solar cells are emerging photovoltaics (PV) technologies. In the last decade, their power conversion efficiency have reached 25.7 % and 31.3% respectively [1,2]. However, these PV technologies still show a large size difference between high efficiency cells, which have an area below the order of the cm2, and industry-viable cells. Hence, the ability to fabricate large area Pvk and Pvk/Si tandem cells showing high efficiency is crucial for industrial development of such technologies. This goal requires deposition process adaptation for every constitutive material layer in these solar cells. Particularly, the electron selective layer deposition is mostly performed by spin-coating, which is a non-adapted process for tens of nanometres-thick films on top of large area and possibly textured substrates. Atomic Layer Deposition (ALD) on the contrary appears to be very attractive for such thin film growth, especially in the tandem cells case, for which the Si bottom cell surface is usually textured.The work realized during this experimental thesis focuses on the study of the influence of integrating an ALD-grown tin dioxide (SnO2) electron selective layer in Pvk-based solar cells.First, ALD-grown SnO2 thin films properties are investigated and compared to the properties of reference spin-coated SnO2 layers. Some differences, notably in their optical and electrical properties, have been identified. The formation of a Pvk film on top of an ALD-grown SnO2 layer is then also analysed and compared to the one of a reference Pvk film, without arising significant differences.With the knowledge of the previous comparisons results in mind, a second part of the work is dedicated to studying the performance of ALD-grown SnO2 electron selective layer by analysing Pvk-based solar cells behaviour. Strong limitations are highlighted, which points out the SnO2/Pvk interface as the probable main limiting region.In a third part, the SnO2/Pvk interface is more precisely investigated thanks to chemical and energetics characterisation techniques. Notably, a work function difference and an ionization energy difference are observed between the ALD-grown SnO2 and the spin-coated SnO2 as well as a difference in the net effective contact area at the SnO2/Pvk interface depending on the SnO2 nature. These results make possible to draw several hypothesis concerning the causes of performance limitations in devices.Finally, the influence of the ALD process modification over SnO2 thin films properties and Pvk-based solar cells behaviour is examined. This study shows that diverse SnO2 thin films annealing as well as a change in ALD growth temperature can affect SnO2 thin films properties with sometimes inducing a modification of solar cells behaviour.The performed studies and their respective results improve the overall understanding of the mechanisms that hinder electron selective layers efficiency in Pvk-based solar cells. This allows the assumption of news ways to integrate successfully an ALD-grown SnO2 electron selective layer in such solar cells, which will participate in the development of Pvk and Pvk/Si tandem solar cells.[1] Green M et al. Solar cell efficiency tables, Progress in Photovoltaics Res. Appl. 2022; 30(7)[2] NREL, Best Research-Cell Efficiency Chart, www.nrel.gov/pv/cell-efficiency.html; Les cellules photovoltaïques (PV) à base de pérovskite (Pvk) et les cellules PV tandem silicium(Si)/Pvk sont des technologies émergentes qui ont vu en quelques années leur rendement de conversion atteindre 25,7 % et 31,3% respectivement [1,2]. Cependant ces technologies PV montrent encore un écart important entre la taille des cellules de haut rendement, inférieure à l’ordre du cm2 et celle des cellules pouvant avoir une application commerciale. Or la possibilité de fabriquer des cellules Pvk et tandem Pvk/Pvk de haut rendement de grande surface est crucial pour leur développement à l’échelle industrielle. Cela requiert l’adaptation des procédés mis en œuvre pour le dépôt de chaque couche de matériau constitutive des cellules. En particulier le dépôt de la couche sélective d’électrons est majoritairement effectué par spin-coating, une méthode non-adaptée pour déposer une couche mince de quelques dizaines de nanomètres d’épaisseur sur une grande surface possiblement texturée. La croissance de couche mince par Atomic Layer Deposition (ALD) se révèle quant à elle très intéressante face à cette problématique, notamment dans le cas des cellules tandem, où la sous-cellule Si présente idéalement une texturation de surface de l’ordre du µm.Les travaux réalisés au cours de cette thèse expérimentale concernent l’étude de l’influence d’une intégration par ALD d’une couche sélective d’électrons en dioxyde d’étain (SnO2) dans les cellules PV à base de pérovskite sur le comportement de ces dernières.Dans un premier axe, les propriétés de couches minces de SnO2 déposées par ALD sont évaluées. La comparaison celles de couches de SnO2 de référence déposées par spin-coating montre des différences de propriétés électriques et optiques notamment. La formation d’un film de Pvk sur une couche de SnO2 déposée par ALD est à son tour analysée et comparée à celle d’un film de référence sans souligner de différences majeures.Un second axe se consacre à l’étude des performances de couches sélectives d’électrons en SnO2 déposées par ALD en examinant le comportement de cellules PV à base de Pvk. De profondes limitations des performances des cellules employant une couche sélective d’électrons en SnO2 déposée par ALD sont relevées. L’analyse de ces limitations pointe l’interface SnO2/Pvk comme étant probablement leur région d’origine majeure.Un troisième axe de travail tente d’étudier plus précisément cette interface au moyen de caractérisations chimiques et physiques. En particulier, une différence du travail de sortie et d’énergie d’ionisation entre les deux types de SnO2 ainsi qu’une différence de surface effective de contact à l’interface SnO2/Pvk entre le cas de référence et celui du SnO2 déposé par ALD sont identifiées, permettant d’établir des hypothèses sur les causes des limitations en dispositif.Enfin, un dernier axe étudie l’impact d’une modification du procédé ALD sur les propriétés des couches de SnO2 et le comportement de cellules PV à base de Pvk. Il est ainsi vu que des recuits et le changement de la température de croissance ALD entraînent des transformations des propriétés des couches de SnO2 qui ne se traduisent pas toutes en une modification du comportement des cellules PV.Les différents travaux réalisés et les résultats qui en découlent permettent d’améliorer la compréhension des mécanismes limitant l’efficacité des couches sélectives d’électrons dans les cellules PV à base de Pvk. Ceci permet ainsi d’imaginer de nouvelles pistes pour intégrer par ALD une couche sélective d’électrons en SnO2 avec succès dans ce type de cellules, ce qui participera au développement de cellules Pvk et tandem Pvk/Si à l’échelle industrielle.[1] Green M et al. Solar cell efficiency tables, Prog. in Phot. Res. Appl. 2022; 30(7)[2] NREL, Best Research-Cell Efficiency Chart, www.nrel.gov/pv/cell-efficiency.html

Solar cells based on lead-free perovskite have demonstrated great potential for next-generation renewable energy. The SCAPS-1D simulation software was used in this study to perform novel device modelling of a lead-free perovskite solar cell of the architecture ITO/WS2/CH3NH3SnI3/P3HT/Au. For the performance evaluation, an optimization process of the different parameters such as thickness, bandgap, doping concentration, etc., was conducted. Extensive optimization of the thickness and doping density of the absorber and electron transport layer resulted in a maximum power-conversion efficiency of 33.46% for our designed solar cell. Because of the short diffusion length and higher defect density in thicker perovskite, an absorber thickness of 1.2 µm is recommended for optimal solar cell performance. Therefore, we expect that our findings will pave the way for the development of lead-free and highly effective perovskite solar cells.

Interface modification plays an important role in enhancing the photoelectric conversion efficiency and stability of organic solar cells. In this work, alkali metal lithium chloride (LiCl) was introduced between indium tin oxide and polyethyleneimine ethoxylate (PEIE) to prepare a double-layer electron transport layer. Results show that the introduction of LiCl has dual functions. The first function is that LiCl can enhance conductivity, thereby facilitating charge collection. The second function is that the double-layer electron transport layer based on LiCl can induce the crystallization of active layer, thereby enhancing charge transport. Devices with LiCl/PEIE double layer achieve a high power conversion efficiency (PCE) of 3.84%, which is 21.5% higher than that of pristine devices (the PCE of pristine devices with pure PEIE interface layer is 3.16%).

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.

SnO2 nanorods were grown on two kinds of seed layers formed from SnCl2·2H2O and SnO2 nanoparticles precursors, respectively, and used as one-dimensional electron transport materials to fabricate perovskite solar cell (PSCs). Effects of the seed layers on morphology, structure, optical properties of SnO2 nanorods and perovskite films, charge transfer at SnO2/perovskite interfaces as well as device performance were investigated by utilizing field emission scanning electron microscopy (SEM), X-ray diffraction (XRD), ultraviolet-visible-near infrared spectroscopy(UV-vis), steady-state photoluminescence spectroscopy (PL) and volt-ampere characteristic curves (J-V). The results show that more dense seed layers can be formed from SnO2 nanoparticles and SnO2 nanorods films formed from SnO2 nanoparticles are more smooth and uniform relative to those grown from SnCl2·2H2O. The perovskite films deposited on the former show better crystallization quality and higher light absorption. The maximum efficiency of the device based on the SnO2 nanorods is 12.93%. This work demonstrates that SnO2 nanoparticles are a kind of excellent seed layer material for growing SnO2 nanorods films, and lays foundation for the preparation of high-performance perovskite solar cells based on one-dimensional electron transport materials.

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.

Tungsten oxide (WOx) thin films were synthesized through the RF magnetron sputtering method by varying the sputtering power from 30 W to 80 W. Different investigations have been conducted to evaluate the variation in different morphological, optical, and dielectric properties with the sputtering power and prove the possibility of using WOx in optoelectronic applications. An Energy Dispersive X-ray (EDX), stylus profilometer, and atomic force microscope (AFM) have been used to investigate the dependency of morphological properties on sputtering power. Transmittance, absorbance, and reflectance of the films, investigated by Ultraviolet-Visible (UV-Vis) spectroscopy, have allowed for further determination of some necessary parameters, such as absorption coefficient, penetration depth, optical band energy gap, refractive index, extinction coefficient, dielectric parameters, a few types of loss parameters, etc. Variations in these parameters with the incident light spectrum have been closely analyzed. Some important parameters such as transmittance (above 80%), optical band energy gap (~3.7 eV), and refractive index (~2) ensure that as-grown WOx films can be used in some optoelectronic applications, mainly in photovoltaic research. Furthermore, strong dependencies of all evaluated parameters on the sputtering power were found, which are to be of great use for developing the films with the required properties.

Recently, the design and fabrication of lead (Pb)-free perovskite or perovskite-like materials have received great interest for the development of perovskite solar cells (PSCs). Manganese (Mn) is a less toxic element, which may be an alternative to Pb. In this work, we explored the role of NH3(CH2)2NH3MnCl4 perovskite as a light absorber layer via SCAPS-1D. A Pb-free PSC device (FTO/TiO2/NH3(CH2)2NH3MnCl4/spiro-OMeTAD/Au) was simulated via SCAPS-1D software. The simulated Pb-free PSCs (FTO/TiO2/NH3(CH2)2NH3MnCl4/spiro-OMeTAD/Au) showed decent power conversion efficiency (PCE) of 20.19%. Further, the impact of the thickness of absorber (NH3(CH2)2NH3MnCl4), electron transport (TiO2), and hole-transport (spiro-OMeTAD) layers were also investigated. Subsequently, various electron transport layers (ETLs) were also introduced to investigate the role of ETL. In further studies, an NH3(CH2)2NH3MnCl4-based PSC device (FTO/TiO2/NH3(CH2)2NH3MnCl4/spiro-OMeTAD/Au) was also developed (humidity = ~30–40%). The fabricated PSCs displayed an open circuit voltage (Voc) of 510 mV with a PCE of 0.12%.

The efficiency and stability of perovskite solar cells (PSCs) depend not only on the perovskite film quality, but they are also influenced by the charge carriers of both the electron and hole transport layers (ETL and HTL). Doping of the carrier transport layers is considered one of effective technique applied to enhance the efficiency and performance of the PSCs. FK209 cobalt TFSI and lithium TFSI salt were investigated as dopants for mesoporous TiO2 (M-TiO2) in the ETL. Herein, FK209 cobalt doping offers improved conductivity, reproducibility and stability compared to other doping or undoped M-TiO2 control device. It has been found that an optimum concentration of 2.5 mg FK209 cobalt in the M-TiO2 has resulted in an efficiency of 15.6% on 0.36 cm2 active device area, whereas, the undoped M-TiO2 yielded an average efficiency of 10.8%. The enhanced efficiency is due to the improved conductivity of the ETL while maintaining high transparency and low surface roughness with FK209 doping. The M-TiO2 doped with FK209 has a transparency of the 90% over the visible range and its measured energy gap was 3.59 eV. Perovskite films deposited on the M-TiO2 doped with FK209 has also a lower PL intensity indicating faster charge extraction. The measured lifetime of the perovskite films deposited on the optimised M-TiO2 film was 115.8 ns.

All-polymer solar cells (all-PSCs) are organic solar cells in which both the electron donor and the acceptor are polymers and are considered more promising in large-scale production. Thanks to the polymerizing small molecule acceptor strategy, the power conversion efficiency of all-PSCs has ushered in a leap in recent years. However, due to the electrical properties of polymerized small-molecule acceptors (PSMAs), the FF of the devices is generally not high. The typical electron transport material widely used in these devices is PNDIT-F3N, and it is a common strategy to improve the device fill factor (FF) through interface engineering. This work improves the efficiency of all-polymer solar cells through interfacial layer engineering. Using PDINN as the electron transport layer, we boost the FF of the devices from 69.21% to 72.05% and the power conversion efficiency (PCE) from 15.47% to 16.41%. This is the highest efficiency for a PY-IT-based binary all-polymer solar cell. This improvement is demonstrated in different all-polymer material systems.

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.

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.

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.

Highlights The (SnO2-cPCN) ETL shows superior electron mobility of 3.3 × 10−3 cm2 V−1 s−1, which is about three times higher than that of pristine SnO2.The less wettable SnO2-cPCN leads to perovskite layers with reduced grain boundaries and enhanced qualities due to suppressed heterogeneous nucleation of perovskite.The PSCs based on SnO2-cPCN showed negligible J–V hysteresis and two champion PCE of 23.17% and 20.3% on devices with 0.1 and 1 cm2 active area, respectively. Supplementary Information The online version contains supplementary material available at 10.1007/s40820-021-00636-0., Efficient electron transport layers (ETLs) not only play a crucial role in promoting carrier separation and electron extraction in perovskite solar cells (PSCs) but also significantly affect the process of nucleation and growth of the perovskite layer. Herein, crystalline polymeric carbon nitrides (cPCN) are introduced to regulate the electronic properties of SnO2 nanocrystals, resulting in cPCN-composited SnO2 (SnO2-cPCN) ETLs with enhanced charge transport and perovskite layers with decreased grain boundaries. Firstly, SnO2-cPCN ETLs show three times higher electron mobility than pristine SnO2 while offering better energy level alignment with the perovskite layer. The SnO2-cPCN ETLs with decreased wettability endow the perovskite films with higher crystallinity by retarding the crystallization rate. In the end, the power conversion efficiency (PCE) of planar PSCs can be boosted to 23.17% with negligible hysteresis and a steady-state efficiency output of 21.98%, which is one of the highest PCEs for PSCs with modified SnO2 ETLs. SnO2-cPCN based devices also showed higher stability than pristine SnO2, maintaining 88% of the initial PCE after 2000 h of storage in the ambient environment (with controlled RH of 30% ± 5%) without encapsulation. Supplementary Information The online version contains supplementary material available at 10.1007/s40820-021-00636-0.

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

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.

The performance of the electron transport layer (ETL) plays a critical role in extending the operational lifespan of organic photovoltaic devices. ZnO is an excellent electron transport layer used in the printable organic photovoltaic cells. A comparison of Ca and ZnO as the ETL in encapsulated bulk heterojunction OPV devices has been undertaken with the device stability dependence on light soaking, temperature, irradiance, and thermal cycling recorded. It was observed that the OPV devices using Ca ETL decayed faster than the ZnO ETL devices under the same light illumination. The degradation in a Ca ETL device is ascribed to the formation of an insulating calcium oxide layer at the ETL interfaces. Photoluminescence (PL) spectroscopy revealed a higher PL signal for the degraded Ca ETL devices compared to the ZnO ETL devices. Power conversion efficiency (PCE) of the ZnO ETL devices was found to be much more stable than the Ca devices. The PCE for ZnO ETL devices still retained 40% of their initial value while the Ca ETL devices failed completely over the period of 18 days in the study, leading to a clear outcome of the study.