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

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

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

[Display omitted] • Organic solar cells (OSCs) are great for internet of things because these work with versatility and can be used both indoors and outdoors. • Inverted configuration makes OSCs more stable and efficient than the conventional one. • Successful exploration of ZnO and Ga-doped ZnO based electron transport layer (ETL) for improved light harvesting by inverted OSC. • Fine-tuned doping concentration in ZnO yield 10.96 % and 4.95 % power conversion efficiency under 1-sun and 1000 lx halogen. • Ga-doping in ZnO improves the photostability of OSC by decreasing oxygen vacancies and retarding its formation under sustained light exposure. Organic solar cells (OSCs) are gaining attention for powering Internet of Things devices due to their impressive power conversion efficiency, flexibility, and slim designs suitable for both indoor and outdoor. The focus on inverted-structured OSCs is increasing due to their superior stability compared to conventional OSCs. This study investigates the use of inverted OSCs with electron transport layers (ETL) made from ZnO and Ga-doped ZnO for light harvesting. OSCs were fabricated using PM6:ITIC-4F as the active layer, and the impact of ZnO doping (Ga) concentration was examined under 1-sun and 1000 lx halogen. Optimizing the doping concentration significantly improved device performance, with PCE values of 10.96 % and 4.95 % for optimally doped ZnO under 1-sun conditions and halogen lamps, respectively. A comparison of photostability under 1-sun and 1000 lx halogen, with varying light soaking durations (0–240 min), showed that Ga-doping in the ZnO ETL improved photostability by reducing oxygen vacancies and slowing down their formation during continuous light exposure. This decrease in oxygen vacancies and enhancement of grain boundaries positively affected charge transport, leading to higher PCE. In summary, Ga-doped ZnO ETL in inverted OSCs demonstrates improved performance and photostability, making them promising for various light harvesting applications. [ABSTRACT FROM AUTHOR]

Interest in perovskite solar cell (PSC) research is increasing because PSC has a remarkable power conversion efficiency (PCE), which has notably risen to 28.3 %. However, commercialization of PSCs faces a significant obstacle due to their stability issues. This review article primarily focuses on several key aspects of PSCs, including different types of solar cells, their construction and operational mechanisms, efficiency, and overall stability. It explains the structure and functioning of PSCs, covering materials and components used for absorber layer, electron-transport layer, hole-transport layer, and electrodes. This review emphasized stability challenges associated with PSCs and discussed various factors and issues contributing to the degradation of these solar cells over time. It then provided a concise overview of different strategies and ongoing efforts taken to enhance the stability of PSCs. It also summarized various approaches used to improve their durability. In summary, this article offers a comprehensive exploration of PSCs, encompassing their construction, operation, improvement in efficiency, and obstacles related to their long-term stability. Furthermore, it addresses factors influencing PSC stability and outlines future challenges, focusing on prolonging their lifespan and enhancing stability for broader applications. Finally, this article has tackled various possible solutions to address the challenges encountered by the PSCs. [ABSTRACT FROM AUTHOR]

In the present article, an FTO/n-ZnO/SnS/Sb 2 S 3 /Au heterojunction photovoltaic cell structure was modeled and the cell performance in terms of output parameters viz. open circuit voltage (V oc), short-circuit current density (J sc), efficiency (η) and fill factor (FF) by varying carrier concentration, and thickness of different layers involved, was studied at ambient conditions. The overall theoretical performance of the designed photovoltaic cell was examined using SCAPS 1-D simulation programme. The simulation programme operates by resolving semiconductor equations such as the Poisson equation, drift-diffusion equation, and continuity equation for both electrons and holes. The equations are generally solved in one-dimension (1D) in a steady state condition. The role of Sb 2 S 3 HTL on the performance study of tin sulfide chalcogenide-based heterojunction photovoltaic cell (HPVC) was also analyzed. Moreover, the impact of functioning temperature between 273 K and 350 K on the performance of photovoltaic cell was observed, and an increase in temperature resulted in poor performance. The impact of different metal back contact work functions and some more electrical parameters viz. series-shunt resistances, defect concentration of layers and interfaces, and radiative recombination coefficients were also observed on HPVC. The simulation results revealed that the HTL Sb 2 S 3 forms proper band alignment with the SnS chalcogenide absorber layer and enhanced the efficiency, η of HPVC by lessening the carrier recombination at the rear contact side. The dislocation and interface defect reduced significantly which leads to the smooth conduction of hole carriers, therefore, preventing of minority carriers to recombine within the absorber. A significant increase in the efficiency ∼33.24 % together with performance cell parameters J sc ∼34.38 mA/cm2, V oc ∼1.09 V, and FF ∼88.49 % was observed. [Display omitted] [ABSTRACT FROM AUTHOR]

For inverted organic solar cells (IOSC), the interface contacts between the ZnO electron transport layer and the organic active layer play an important role in device performance and stability. The light absorption effect is one of the major disadvantages of IOSC when metal oxides are used as the electron transport layer (ETL). Oxide ETL primarily causes the above effect due to the energy barrier, deep level defects and excess carrier tunneling. In this work, we studied the effects of annealing ZnO films under various environmental conditions. ZnO films were synthesized by the sol-gel method, and the films were annealed at a temperature of 450 °C in air, an inert nitrogen gas (N 2), oxygen (О 2) and vacuum. SEM images and EDX spectra of the surface of thin ZnO films showed a change in thickness and the quantitative content of Zn/O elements. It was found that the annealing environment has a great influence on the morphology and thickness of ZnO films. Numerical calculations of the extinction, absorption, and scattering spectra of ZnO nanoparticles of different sizes are in good agreement with the results of measurements. Volt-ampere and electrical impedance measurements showed that ZnO films not only change the overall electrical resistance of devices to the contribution of the ZnO film resistance, but also change the electrical properties of the P3HT-PC61BM heterojunction. [ABSTRACT FROM AUTHOR]

Zinc oxide nanorod arrays (ZnO NRAs) have been previously introduced as electron transport layer (ETL) of perovskite solar cells (PSCs) due to their high electron mobility and unique textured morphology. However, the presence of hydroxyl and oxygen vacancies on the surface of bare intrinsic ZnO NRAs may act as defect centers leading to carrier nonradiative recombination and the device photovoltaic performance degradation. Here, we propose a mutilayer SnO 2 /Al-doped ZnO nanorod arrays/SnO 2 (SnO 2 /AZO NRAs/SnO 2) composite to be utilized as ETL of all-inorganic CsPbBr 3 PSCs. The influence of AZO NRAs with various Al ion (Al3+) doping content on the performance of CsPbBr 3 PSCs was explored. The hole-free carbon-based CsPbBr 3 PSCs with an architecture of FTO/SnO 2 /AZO NRAs/SnO 2 /CsPbBr 3 /carbon based on 1 at% AZO NRAs exhibited the best photovoltaic performance with a champion power conversion efficiency (PCE) of 7.11 %, open-circuit voltage (V oc) of 1.46 V, short-circuit current density (J sc) of 6.88 mA/cm2, and fill factor (FF) of 71.1 %, compared with the bare intrinsic ZnO-based counterpart with a PCE of 3.45 %, V oc of 0.80 V, J sc of 8.46 mA/cm2, and FF of 51 %, respectively. The photovoltaic performance enhancement can be atrributed to enhanced light collection and electron extraction capability, with lower open-circuit voltage loss and more suitable interface band alighment. It is notable that the AZO NRAs were prepared by a facile electrodeposition approach to obtain large-area textured ETLs. This strategy may also be applicable to the photovoltaic performance improvemet of all types of PSCs. [ABSTRACT FROM AUTHOR]

In this study, green SnO 2 @TiO 2 nanocomposites were initially synthesized using an extract from the Calotropis plant as an electron transfer material for fabricating perovskite solar cells (PSCs). Further, plasmon impregnation (Ag-NPs) into the SnO 2 @TiO 2 nanocomposites yielded nanocomposite (TiO 2 @SnO 2 /Ag) films. The effect of doping silver into the SnO 2 @TiO 2 nanocomposites was investigated in detail to gain insights into how it influences the photovoltaic performance of the PSC. It resulted in enhanced quenching of photoluminescence compared to TiO 2 and TiO 2 @SnO 2 electron transport layers (ETLs), indicating faster charge extraction. PSCs utilizing the TiO 2 @SnO 2 /Ag ETL showed significantly improved performance with a power conversion efficiency of 22.2 %, a higher fill factor, and reduced hysteresis compared to cells with TiO 2 and TiO 2 @SnO 2 ETLs. The characterization of the nanocomposites revealed that the TiO 2 @SnO 2 /Ag ETL led to perovskite films with improved crystallinity, morphology, charge separation, and transfer properties. Electrochemical impedance spectroscopy confirmed the TiO 2 @SnO 2 /Ag ETL facilitated faster charge transfer and lower recombination at interfaces. Finally, the TiO 2 @SnO 2 /Ag ETL-based devices exhibited superior long-term stability in air, maintaining over 87 % of their initial efficiency. This work demonstrates that the incorporation of TiO 2 @SnO 2 /Ag nanocomposites is effective for developing high-performance and stable PSCs. • Green SnO 2 @TiO 2 nanocomposites were initially synthesized using an extract from the Calotropis plant. • Ag NPs were doped into the SnO 2 @TiO 2 nanocomposites. • PSCs were fabricated with TiO2@SnO2/Ag as electron transport layer. • The optimized cell showed an efficiency of 22.2 %. [ABSTRACT FROM AUTHOR]

Abstract A multi-dimensional conductive heterojunction structure, composited by TiO2, SnO2, and Ti3C2T X MXene, is facilely designed and applied as electron transport layer in efficient and stable planar perovskite solar cells. Based on an oxygen vacancy scramble effect, the zero-dimensional anatase TiO2 quantum dots, surrounding on two-dimensional conductive Ti3C2T X sheets, are in situ rooted on three-dimensional SnO2 nanoparticles, constructing nanoscale TiO2/SnO2 heterojunctions. The fabrication is implemented in a controlled low-temperature anneal method in air and then in N2 atmospheres. With the optimal MXene content, the optical property, the crystallinity of perovskite layer, and internal interfaces are all facilitated, contributing more amount of carrier with effective and rapid transferring in device. The champion power conversion efficiency of resultant perovskite solar cells achieves 19.14%, yet that of counterpart is just 16.83%. In addition, it can also maintain almost 85% of its initial performance for more than 45 days in 30–40% humidity air; comparatively, the counterpart declines to just below 75% of its initial performance.

Perovskite solar cells have the advantages of low material cost, simple production process and high photoelectric conversion efficiency, and their development prospects are bright. Carbon materials are used in various components of perovskite solar cells due to their low cost, high electrical conductivity, hydrophobicity and chemical stability to improve battery performance and reduce costs. Based on the dimensionality of the carbon materials used in perovskite solar cells, the zero-dimensional C60, carbon quantum dots and graphene quantum dots, one-dimensional carbon nanotubes, two-dimensional graphene and the application of derivatives, graphyne, and three-dimensional graphite in perovskite solar cells were described in this paper, and it is of great importance for the realization of low-cost commercialization and large-scale manufacturing of perovskite solar cells in the future.

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.

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%.

Perovskite solar cells (PSCs) made their mark in the photovoltaic research community due to their accelerating efficiencies, bandgap tunability, ease of fabrication, choice of substrates, etc. The electron transport layer (ETL) plays a decisive role in determining the performance and scalability of PSCs. SnO2 is a potential candidate for ETL in PSCs due to its high transmittance, low sintering temperatures, and suitable deep conduction and valence band positions that allows efficient electron extraction at the interfaces. In this work, we developed a simple, solution-processable low-temperature deposition of SnO2 on fluorine-doped tin oxide (FTO) glass substrates employing dip-coating technique for the first time. The number of dipping cycles are optimized to attain uniform coverage of the SnO2 layer on FTO. Formamidinium lead tri-iodide (FAPbI3) perovskite is deposited onto the dip-coated SnO2 electrode by vapor assisted solution process. XRD reveals the successful SnO2 phase formation by a low-temperature dip-coating method and FAPbI3 perovskite film formation by vapor assisted solution process with an unremarkable presence of the photo inactive δ phase. The surface morphology of the FAPbI3 films is smooth with an average grain size of 220 nm. A preliminary study on the planar device's photovoltaic performance using CuSCN as hole transport material (HTM) and Au as back contact exhibited a power conversion efficiency of 3.2% using four deposition cycles of SnO2 by dip-coating as the electron transport layer. This study demonstrates the utilization of dip-coating as a cost-effective method to deposit ETL that paves the way for PSCs' scale-up.

Abstract Low‐temperature solution‐processed TiO2 nanocrystals (LT‐TiO2) have been extensively applied as electron transport layer (ETL) of perovskite solar cells (PSCs). However, the low electron mobility, high density of electronic trap states, and considerable photocatalytic activity of TiO2 result in undesirable charge recombination at the ETL/perovskite interface and notorious instability of PSCs under ultraviolet (UV) light. Herein, LT‐TiO2 nanocrystals are in situ fluorinated via a simple nonhydrolytic method, affording formation of Ti─F bonds, and consequently increase electron mobility, decrease density of electronic trap states, and inhibit photocatalytic activity. Upon applying fluorinated TiO2 nanocrystals (F‐TiO2) as ETL, regular‐structure planar heterojunction PSC (PHJ‐PSC) achieves a champion power conversion efficiency (PCE) of 22.68%, which is among the highest PCEs for PHJ‐PSCs based on LT‐TiO2 ETLs. Flexible PHJ‐PSC devices based on F‐TiO2 ETL exhibit the best PCE of 18.26%, which is the highest value for TiO2‐based flexible devices. The bonded F atoms on the surface of TiO2 promote the formation of Pb─F bonds and hydrogen bonds between F− and FA/MA organic cations, reinforcing interface binding of perovskite layer with TiO2 ETL. This contributes to effective passivation of the surface trap states of perovskite film, resulting in enhancements of device efficiency and stability especially under UV light.

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

The heterostructure of graphene and ZnO nanorods is attractive as a tin oxide-free electron transport layer for a broad variety of excitonic photovoltaic technologies. This work focuses on the effect of electrodeposition variables on morphology and performance of vertically aligned zinc oxide nanorods (ZVNRs) on graphene. This in situ growth technique has potential for fabrication of a wide variety of graphene heterostructures under mild synthesis conditions to prevent graphene damage. Large area graphene was grown by chemical vapor deposition, stacked up to four atomic layers, and transferred to glass. ZVNRs were electrodeposited on the graphene-coated glass and the topography was controlled by changing the electrodeposition parameters of the time, temperature, stirring, and seeding layers. The mechanisms controlling the cathodic electrodeposition of nanocrystals on graphene were studied by scanning electron microscopy of the ZVNRs topography. The effect of the topography of the ZVNRs on the electron generation and transport was studied for photoanode application in reference dye-sensitized solar cells. The charge transfer resistance and kinetics of the materials as photoanodes were measured with the techniques of linear sweep voltammetry, open circuit voltage decay, and electrochemical impedance spectroscopy. The optimization of ZnO growth resulted in an increase of the surface-to-volume ratio of the electrode from 10 to 250 mm−1, 60-fold increase of electron lifetime and ten-fold increase in power output. The results of this study provide fundamental understanding for designing electrodeposition processes of the hybrid ZVNR/graphene material. [ABSTRACT FROM AUTHOR]

Summary: Lead halide perovskite has been found to be a promising contender for photovoltaic (PV) applications. Solution‐processed perovskite solar cells (PSCs) have attracted excessive consideration owing to their high performance and low manufacture cost. However, complicated deposition of expensive metal electrodes is incompatible with large‐scale and low‐cost fabrication of perovskite PV devices and thus hinders their commercialization. Various combinations of the materials have been used as hole transport layer (HTL) and electron transport layer (ETL) to enhance the conversion efficiency and stability of PSCs. In this regard, layered two‐dimensional materials like graphene and transition metal dichalcogenides (TMDCs) have revealed fascinating properties that make them a promising material for PV applications. The review focuses on the applications of 2D materials thereby using them as HTL and ETL in PSCs. We have discussed the effect of Gr and graphene quantum dots (GQDs) as HTL in composition with frequently used ZnO and TiO2. Furthermore, the role of TMDCs like MoS2, WS2 as ETL, and HTL have been studied. Besides, the effect of the synthesis approach on PV performance is also discussed. The ultrasonic spray pyrolysis method for the synthesis of MoS2 has made an effective impact on PV performance of the cell. A detailed study of TMDCs with organic HTLs like P3HT and so on is also provided. Therefore, the utilization of layered 2D materials as HTL and ETL in PSCs enhances the overall power conversion efficiency (PCE) of the device, facilitating the fast charge transport and provides high thermal and mechanical stability. Thus, the combination of strong light absorber with highly conductive layered materials can be exploited as a promising contender for efficient, stable, and cost‐effective solar cells for future energy harvesting technological applications. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Solar electricity is an unlimited source of sustainable fuels, yet the efficiency of solar cells is limited. The efficiency of perovskite solar cells improved from 3.9% to reach 25.5% in just a few years. Perovskite solar cells are actually viewed as promising by comparison with dye-sensitized solar cells, organic solar cells, and the traditional solar cells made of silicon, GaAs, copper indium gallium selenide (CIGS), and CdTe. Here, we review bare and doped metal oxide electron transport layers in the perovskite solar cells. Charge transfer layers have been found essential to control the performance of perovskite solar cells by tuning carrier extraction, transportation, and recombination. Both electron and hole transport layers should be used for charge separation and transport. TiO2 and 2,2′,7,7′-Tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9′-spirobifluorene are considered as the best electron and hole transport layers. Metal oxide materials, either bare or doped with different metals, are stable, cheap, and effective. [ABSTRACT FROM AUTHOR]

Perovskites are the materials or compounds having a structure similar to calcium titanium oxide (CaTiO3). These materials possess the basic structure of ABX3, in which A & B are the cations with +1 and +2 electron vacancy and X is an anion which may be either halogen or oxygen. Perovskites are chiefly being used in solar cells in the photo absorbing layer for solar to electrical energy conversion with relatively high efficiencies, besides their use in LEDs, photodetectors, X-ray detectors, lasers etc. The power conversion efficiency (PCE) of Perovskite solar cell (PSC) has increased from 10% in the year 2012 to 29.1% in 2020 and are promising to cross the theoretical maximum (Shockley-Queisser) limit of 33% for conventional silicon solar cells, besides having great thermal and mechanical stability values. Toxicity due to the presence of lead and associated instability of PSCs have led to the intensive research in lead-free perovskite solar cells (LF-PSCs). In this review article we have tried to explore the current status of synthesis, properties and applications of perovskites in PSCs, particularly lead-free perovskites, and will suggest future prospects in this widely attracted field of non-conventional energy generation. [ABSTRACT FROM AUTHOR]

Graphitic carbon nitride is in situ synthesized and introduced into TiO 2 -based perovskite solar cell via a facile glass-assisted annealing route, leading to a highest PCE of 20.46%, which is ca. 20% enhancement in contrast with pristine cell (17.18%). [Display omitted] • 1. Graphitic carbon nitride is in situ synthesized via a glass-assisted annealing route. • 2. ETLs with g-C 3 N 4 can improve the optoelectronic properties and long-term stability. • 3. PSC fabricated on g-C 3 N 4 modified ETL achieves a maximum PCE of 20.46%. TiO 2 -based electron transport layers (ETLs) show tremendous advantages in constructing efficient perovskite solar cells (PSCs), but the power conversion efficiency (PCE) needs further improvements. Thus, in this study, graphitic carbon nitride (g-C 3 N 4), a typical two-dimensional material, was synthesized in-situ and introduced into TiO 2 -based ETLs as an additive via a facile glass-assisted annealing route. The results demonstrated that the addition of g-C 3 N 4 positively influenced the crystalline quality of the perovskite layers, as well as the conductivity and photovoltaic properties of the devices. Furthermore, favorable energy level alignment facilitated rapid migration of electrons and suppressed charge recombination at the interfaces. Consequently, the champion device fabricated using the g-C 3 N 4 -modified ETL achieved a maximum PCE of 20.46% owing to the remarkable improvement in the V oc , J sc , and fill factor. The PCE is approximately 20% higher than that obtained for the pristine device, i.e., 17.18%. [ABSTRACT FROM AUTHOR]

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

Low‐temperature solution‐processed TiO2 nanocrystals (LT‐TiO2) have been extensively applied as electron transport layer (ETL) of perovskite solar cells (PSCs). However, the low electron mobility, high density of electronic trap states, and considerable photocatalytic activity of TiO2 result in undesirable charge recombination at the ETL/perovskite interface and notorious instability of PSCs under ultraviolet (UV) light. Herein, LT‐TiO2 nanocrystals are in situ fluorinated via a simple nonhydrolytic method, affording formation of Ti─F bonds, and consequently increase electron mobility, decrease density of electronic trap states, and inhibit photocatalytic activity. Upon applying fluorinated TiO2 nanocrystals (F‐TiO2) as ETL, regular‐structure planar heterojunction PSC (PHJ‐PSC) achieves a champion power conversion efficiency (PCE) of 22.68%, which is among the highest PCEs for PHJ‐PSCs based on LT‐TiO2 ETLs. Flexible PHJ‐PSC devices based on F‐TiO2 ETL exhibit the best PCE of 18.26%, which is the highest value for TiO2‐based flexible devices. The bonded F atoms on the surface of TiO2 promote the formation of Pb─F bonds and hydrogen bonds between F− and FA/MA organic cations, reinforcing interface binding of perovskite layer with TiO2 ETL. This contributes to effective passivation of the surface trap states of perovskite film, resulting in enhancements of device efficiency and stability especially under UV light. [ABSTRACT FROM AUTHOR]

ZnO quantum dots (QDs) with average particle size of 4.4 nm were prepared using a low temperature processing solvothermal route. ZnO QD based thin films were then prepared from the ZnO QD based solution using spin coating technique and annealed at 250, 350 and 450 °C. The average grain size and energy band gap of ZnO were respectively increased and decreased from 5.5 to 22.9 nm and 3.37 to 3.27 eV upon increasing the annealing temperature up to 450 °C. The photoluminescence analysis showed that the as-coated ZnO film and ZnO film annealed at 250 °C have high density of oxygen vacancies; these defects were reduced upon increasing the temperature to 350 and 450 °C. The photoelectric properties of the films were strongly affected by the grain size and the defects present in the films. The photo-to-dark current ratio (PDCR) was decreased from 3723 to 371%, whereas the responsivity was increased from 1.25 to 218 mA/W with the increase of temperature to 450 °C. As-coated and 250 °C-annealed films exhibited better photoresponse than others in terms of PDCR, rise time and fall time due to their larger surface-to-volume ratio, making them promising candidate as electron transport layer in perovskite solar cells. [ABSTRACT FROM AUTHOR]

The highest photoelectric conversion efficiency of organic-inorganic hybrid perovskite solar cells (referred to as perovskite solar cells) has reached 25.5%, and it is one of the most promising solar cells to replace silicon-based solar cells and achieve a wide range of applications. As the basic component of the perovskite solar cell, the electron transport layer plays a vital role in the performance of the cell. This article briefly describes the effects of type(organic polymer materials and metal oxides such as TiO2, ZnO and SnO2) of electron transport layers in perovskite solar cells, size (the length and diameter of the nanowires, the thickness of the thin films) and interface modification on the performance of the devices. This can provide a reference for the works of continuing to improve the performance of perovskite solar cells. [ABSTRACT FROM AUTHOR]

The lead-free double perovskites have recently emerged as promising alternative material for solar cell application. It exhibits encouraging optoelectronic properties, high environmental stability and low toxicity. The double perovskite having two different cations are non-toxic alternatives. The double perovskite Cs2AgBiBr6 has good optical and electronic features. Therefore, it has been used for high-efficiency optoelectronic devices. In this manuscript, we report optimization of active layer thickness of double perovskite Cs2AgBiBr6 for photovoltaic application. For the study, a device FTO/TiO2/Cs2AgBiBr6/Spiro-OMeTAD/Cu was designed. The Solar Cell Capacitance Simulator (SCAPS-1D) was used for one dimensional simulation and analysis. The active layer of 0.1 to 1 μm was used for the study and PCE, Voc, Jsc and FF were obtained using simulation. The optimum active layer thickness was found to be between 0.20 μm to 0.4 μm. The maximum PCE of 3.78 % was found. The solar cell performance can be improvised further by optimizing the defect density of the active layer. Also, the effects of ETL and HTL layer thickness can be further observed for enhancement of PCE. Overall, the encouraging simulation results achieved in this study will provide insightful guidance in replacing commonly used cancerous Pb-based perovskite with eco-friendly, highly efficient inorganic perovskite solar cell. [ABSTRACT FROM AUTHOR]

Semiconductor colloidal quantum rods (QRs) are evolving as potential candidates for future lighting and display applications due to numerous advantages. QRs offer various aids over quantum dots (QDs) in terms of polarized emission, large global Stokes shift, and double the outcoupling efficiency. In this paper, we synthesized CdSe/CdS/ZnS (core/shell/shell) green QRs with an emission wavelength at 520 nm and employed them in QR based light‐emitting diodes (QRLEDs). The QRLED device performance was further optimized by inserting a thin poly (methyl methacrylate) (PMMA) layer in‐between emissive layer and electron transport layer (ETL) (ZnO NP). The PMMA layer is acting as a barrier between the emissive layers to the ETL interface, and thus limit the excess electron injection into the QRs and helps to maintain the balanced charge injection. The fabricated green QRLEDs exhibit excellent optoelectronic performance, such as high brightness of 11890 cd/m2 and an impressive peak external quantum efficiency (EQE) of 5.6 %. Through further tuning the device with a PMMA, we elevated the peak‐EQE up to 6.8%. To the best of our knowledge, these are the best‐reported numbers for the QR based green light‐emitting diodes. [ABSTRACT FROM AUTHOR]

In this work, the effect of some parameters on tin-based perovskite (CH3NH3SnI3) solar cell were studied through device simulation with respect to adjusting the doping concentration of the perovskite absorption layer, its thickness and the electron affinities of the electron transport medium and hole transport medium, as well as the defect density of the perovskite absorption layer and hole mobility of hole transport material (HTM). A device simulator; the one-dimensional Solar Cells Capacitance Simulator (SCAPS‑1D) program was used for simulating the tin-based perovskite solar cells. The current-voltage (J-V) characteristic curve obtained by simulating the device without optimization shows output cell parameters which include; open circuit voltage (Voc) = 0.64V, short circuit current density (Isc) = 28.50mA/, fill factor (FF) = 61.10%, and power conversion efficiency (PCE) = 11.30% under AM1.5 simulated sunlight of 100mW/cm2 at 300K. After optimization, values of the doping concentration, defect density, electron affinity of electron transport material and hole transport material were determined to be: 1.0x1016cm-3, 1.0x1015cm-3, 3.7 eV and 2.3 eV respectively. Appreciable values of solar cell parameters were obtained with Jsc of 31.38 mA/cm2, Voc of 0.84 V, FF of 76.94% and PCE of 20.35%. when compared with the initial device without optimization, it shows improvement of ~1.10 times in Jsc, ~1.80 times in PCE, ~1.31 times in Voc and ~1.26 time in FF. The results show that the lead-free CH3NH3SnI3 perovskite solar cell which is environmentally friendly is a potential solar cell with high theoretical efficiency of 20.35%.

Flexible and printed perovskite solar cells (PSCs) fabricated on lightweight plastic substrates have many excellent potential applications in emerging new technologies including wearable and portable electronics, the internet of things, smart buildings, etc. To fabricate flexible and printed PSCs, all of the functional layers of devices should be processed at low temperatures. Tin oxide is one of the best metal oxide materials to employ as the electron transport layer (ETL) in PSCs. Herein, the synthesis and application of SnO2 quantum dots (QDs) to prepare the ETL of flexible and printed PSCs are demonstrated. SnO2 QDs are synthesized via a solvothermal method and processed to obtain aqueous and printable ETL ink solutions with different QD concentrations. PSCs are fabricated using a slot-die coating method on flexible plastic substrates. The solar cell performance and spectral response of the obtained devices are characterized using a solar simulator and an external quantum efficiency measurement system. The ETLs prepared using 2 wt% SnO2 QD inks are found to produce devices with a high average power conversion efficiency (PCE) along with a 10% PCE for a champion device. The results obtained in this work provide the research community with a method to prepare fully solution-processed SnO2 QD-based inks that are suitable for the deposition of SnO2 ETLs for flexible and printed PSCs.

This work presents the implementation of ultrathin TiO2 films, deposited at room temperature by radio-frequency magnetron sputtering, as electron-selective contacts in silicon heterojunction solar cells. The effect of the working pressure on the properties of the TiO2 layers and its subsequent impact on the main parameters of the device are studied. The material characterization revealed an amorphous structure regardless of the working pressure; a rougher surface; and a blue shift in bandgap in the TiO2 layer deposited at the highest-pressure value of 0.89 Pa. When incorporated as part of the passivated full-area electron contact in silicon heterojunction solar cell, the chemical passivation provided by the intrinsic a-Si:H rapidly deteriorates upon the sputtering of the ultra-thin TiO2 films, although a short anneal is shown to restore much of the passivation lost. The deposition pressure and film thicknesses proved to be critical for the efficiency of the devices. The film thicknesses below 2 nm are necessary to reach open-circuit values above 660 mV, regardless of the deposition pressure. More so, the fill-factor showed a strong dependence on deposition pressure, with the best values obtained for the highest deposition pressure, which we correlated to the porosity of the films. Overall, these results show the potential to fabricate silicon solar cells with a simple implementation of electron-selective TiO2 contact deposited by magnetron sputtering. These results show the potential to fabricate silicon solar cells with a simple implementation of electron-selective TiO2 contact.

The widely used ZnO quantum dots (QDs) as an electron transport layer (ETL) in quantum dot light-emitting diodes (QLEDs) have one drawback. That the balancing of electrons and holes has not been effectively exploited due to the low hole blocking potential difference between the valence band (VB) (6.38 eV) of ZnO ETL and (6.3 eV) of CdSe/ZnS QDs. In this study, ZnO QDs chemically reacted with capping ligands of oleic acid (OA) to decrease the work function of 3.15 eV for ZnO QDs to 2.72~3.08 eV for the ZnO-OA QDs due to the charge transfer from ZnO to OA ligands and improve the efficiency for hole blocking as the VB was increased up to 7.22~7.23 eV. Compared to the QLEDs with a single ZnO QDs ETL, the ZnO-OA/ZnO QDs double ETLs optimize the energy level alignment between ZnO QDs and CdSe/ZnS QDs but also make the surface roughness of ZnO QDs smoother. The optimized glass/ITO/PEDOT:PSS/PVK//CdSe/ZnS//ZnO-OA/ZnO/Ag QLEDs enhances the maximum luminance by 5~9% and current efficiency by 16~35% over the QLEDs with a single ZnO QDs ETL, which can be explained in terms of trap-charge limited current (TCLC) and the Fowler-Nordheim (F-N) tunneling conduction mechanism.

Tin(IV) oxide (SnO2) nanostructures, which possess larger surface areas for transporting electron carriers, have been used as an electron transport layer (ETL) in perovskite solar cells (PSCs). However, the reported power conversion efficiencies (PCEs) of this type of PSCs show a large variation. One of the possible reasons for this phenomenon is the low reproducibility of SnO2 nanostructures if they are prepared by different research groups using various growth methods. This work focuses on the morphological study of SnO2 nanostructures grown by a solvothermal method. The growth parameters including growth pressure, substrate orientation, DI water-to-ethanol ratios, types of seed layer, amount of acetic acid, and growth time have been systematically varied. The SnO2 nanomorphology exhibits a different degree of sensitivity and trends towards each growth factor. A surface treatment is also required for solvothermally grown SnO2 nanomaterials for improving photovoltaic performance of PSCs. The obtained results in this work provide the research community with an insight into the general trend of morphological changes in SnO2 nanostructures influenced by different solvothermal growth parameters. This information can guide the researchers to prepare more reproducible solvothermally grown SnO2 nanomaterials for future application in devices.

Renewable energy methodologies are the key to a sustainable future. PV technology has been raised as one of the most promisor alternatives for energy conversion, due to the use of an inexhaustible source. The third generation of solar devices, present in composition a semiconductor oxide, that work as electron transport material (ETL), receiving and transporting the electron from a photosensitive molecule. TiO 2 performs with efficiency the role of ETL in solar devices, nevertheless, since of the higher cost, other oxides have been studied, as Nb 2 O 5. This work aims to synthetized Nb 2 O 5 by Pechini methodology and applied it as ETL in a solar device. The techniques performed in particle characterization were Scanning Electronic Microscopy (SEM) and X-ray diffraction (XRD). To verify the capability of transport electrons, the electrochemical measurements were applied to V oc /J sc decay, j-V curves, Electrochemical Impedance Spectroscopy (EIS), and Intensity Modulate Photovoltage Spectroscopy (IMVS). The results showed Nb 2 O 5 synthesized in orthorhombic phase able to produce a photosensitive dye-solar device with j = 4.18 mA cm−2, V = 825 mV, FF = 0.4, PCE = 1.38% with slow recombination rate when compare to TiO 2 dye-solar cell. The IMVS and EIS technique present the same accuracy to electron lifetime determination which is confirmed by the t -test performed. [ABSTRACT FROM AUTHOR]

Organic polymer semiconductor‐based polymer solar cells (PSCs) are drawing tremendous research interest for their superior electrical, structural, optical, mechanical, and chemical properties. During the last two decades, immense efforts have been made toward the development of PSCs. Generally, poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is used as hole transport layer (HTL) of PSCs to improve hole extraction efficiency, but highly acidic PEDOT:PSS reduces device lifetime by destroying indium tin oxide (ITO) electrodes and active layers. To avoid this, some have attempted to develop inverted structured PSCs with different electron transport layers (ETLs); however, the power conversion efficiency (PCE) of these devices is limited owing to low electron mobility of their ETLs. Therefore, an attempt is made to improve the PCE of an inverted‐structured PSC by using indium gallium zinc oxide (IGZO) with optimized amount of indium (In), gallium (Ga), and zinc (Zn). Inverted PSCs with ZnO or IGZO (having various molar ratios of In, Ga, and Zn) as ETL with the structure ITO/ETL/PTB7:PC71BM/MoO3/Al are constructed. The PCE of the inverted PSC can be increased from 6.22% to 8.72% by using IGZO with an optimized weight ratio of In, Ga, and Zn as an ETL. [ABSTRACT FROM AUTHOR]

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.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. [ABSTRACT FROM AUTHOR]

This study delves into enhancing the efficiency and stability of perovskite solar cells (PSCs) by optimizing the surface morphologies and optoelectronic properties of the electron transport layer (ETL) using tungsten (W) doping in zinc oxide (ZnO). Through a unique green synthesis process and spin-coating technique, W-doped ZnO films were prepared, exhibiting improved electrical conductivity and reduced interface defects between the ETL and perovskite layers, thus facilitating efficient electron transfer at the interface. High-quality PSCs with superior ETL demonstrated a substantial 30% increase in power conversion efficiency (PCE) compared to those employing pristine ZnO ETL. These solar cells retained over 70% of their initial PCE after 4000 h of moisture exposure, surpassing reference PSCs by 50% PCE over this period. Advanced numerical multiphysics solvers, employing finite-difference time-domain (FDTD) and finite element method (FEM) techniques, were utilized to elucidate the underlying optoelectrical characteristics of the PSCs, with simulated results corroborating experimental findings. The study concludes with a thorough discussion on charge transport and recombination mechanisms, providing insights into the enhanced performance and stability achieved through W-doped ZnO ETL optimization.

This paper reports five novel PDI dimer type electron transport materials (ETMs) employing o-indoloquinoxaline (o-Iq), m-indoloquinoxaline (m-Iq), and cibalackrot (Ci) groups as the core building blocks and presents the twisted structures of PDI dimers coded as PDI-NHR-o-Iq, PDI-o-Iq, PDI-NHR-m-Iq, PDI-m-Iq and PDI-NHR-Ci dyes (see Scheme 1 and 2). We have systematically compared their photophysical, electrochemical, and optoelectronic properties with respect to the reference dye (2PDI-NHR), which is directly connected of two PDI planes. Their calculated HOMO-LUMO energy levels are sufficient for charge transfer to the perovskite material so that structure-photovoltaic performance relationship of synthesized ETM dyes can be evaluated. When the binding position of indoloquinoxaline group between PDI rings are changed from o- to m- positions, most of the photophysical and electrochemical properties of PDI dimer are dramatically changed, finally improving the photovoltaic performances., (© 2024 Wiley-VCH GmbH.)

Perovskite solar cells (PSCs), which are constructed using organic-inorganic combination resources, represent an upcoming technology that offers a competitor to silicon-based solar cells. Electron transport materials (ETMs), which are essential to PSCs, are attracting a lot of interest. In this section, we begin by discussing the development of the PSC framework, which would form the foundation for the requirements of the ETM. Because of their exceptional electronic characteristics and low manufacturing costs, perovskite solar cells (PSCs) have emerged as a promising proposal for future generations of thin-film solar energy. However, PSCs with a compact layer (CL) exhibit subpar long-term reliability and efficacy. The quality of the substrate beneath a layer of perovskite has a major impact on how quickly it grows. Therefore, there has been interest in substrate modification using electron transfer layers to create very stable and efficient PSCs. This paper examines the systemic alteration of electron transport layers (ETLs) based on electron transfer layers that are employed in PSCs. Also covered are the functions of ETLs in the creation of reliable and efficient PSCs. Achieving larger-sized particles, greater crystallization, and a more homogenous morphology within perovskite films, all of which are correlated with a more stable PSC performance, will be guided by this review when they are developed further. To increase PSCs' sustainability and enable them to produce clean energy at levels previously unheard of, the difficulties and potential paths for future research with compact ETLs are also discussed.

The spontaneous orientation polarization (SOP) of a permanent dipole moment of the molecule induces a giant surface potential (GSP) in an organic semiconductor film, and GSP is expected to be a crucial parameter for understanding the operational mechanism of organic light-emitting diodes (OLEDs). This study demonstrates that the voltage-dependent migration of a carrier recombination zone induced by a polar electron transporting layer (ETL) having a positive SOP causes a decline in the overall performance of the OLED in triplet-triplet upconversion (TTU) based on OLEDs. Specifically, the TTU efficiency in an OLED with 2,2',2″-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) as the ETL decreased by 20% due to the reduction of electrically generated triplet exciton density. This decrease resulted in a lower external electroluminescence (EL) quantum efficiency (EQE) of 5.4% at 1 mA cm -2 , while the OLED with a nonpolar ETL resulted in an EQE of around 8.1% at 1 mA cm -2 . We confirmed a shift in the recombination zone from the current density dependence of the EL spectra in the OLEDs. Our results indicate that the fixed carrier recombination zone near a hole transport layer and an emitting layer (HTL/EML) strongly enhanced the TTU process, while the polar EML/ETL interface induced the migration of the recombination zone depending on voltage, resulting in the decrease of triplet exciton density.

Perovskite solar cells (PSCs) stand at the forefront of photovoltaic research, with current efficiencies surpassing 26.1%. This review critically examines the role of electron transport materials (ETMs) in enhancing the performance and longevity of PSCs. It presents an integrated overview of recent advancements in ETMs, like TiO 2 , ZnO, SnO 2 , fullerenes, non-fullerene polymers, and small molecules. Critical challenges are regulated grain structure, defect passivation techniques, energy level alignment, and interfacial engineering. Furthermore, the review highlights innovative materials that promise to redefine charge transport in PSCs. A detailed comparison of state-of-the-art ETMs elucidates their effectiveness in different perovskite systems. This review endeavors to inform the strategic enhancement and development of n-type electron transport layers (ETLs), delineating a pathway toward the realization of PSCs with superior efficiency and stability for potential commercial deployment., (© 2024 Wiley‐VCH GmbH.)

Near-infrared (NIR) organic photodetectors (OPDs) are pivotal in numerous technological applications due to their excellent responsivity within the NIR region. Polyethylenimine ethoxylated (PEIE) has conventionally been employed as an electron transport layer (hole-blocking layer) to suppress dark current ( J D ) and enhance charge transport. However, the limitations of PEIE in chemical stability, processing conditions, environmental impact, and absorption range have spurred the development of alternative materials. In this study, we introduced a novel solution: a hybrid of sol-gel zinc oxide (ZnO) and N , N '-bis( N -dimethylpropan-1-amine oxide)perylene-3,4,9,10-tetracarboxylic diimide (PDINO) as the electron transport layer for NIR-OPDs. Our fabricated OPD exhibited significantly improved responsivity, reduced internal traps, and enhanced charge transfer efficiency. The detectivity, spanning from 400 to 1100 nm, surpassed ∼5 × 10 N -dimethylpropan-1-amine oxide)perylene-3,4,9,10-tetracarboxylic diimide (PDINO) as the electron transport layer for NIR-OPDs. Our fabricated OPD exhibited significantly improved responsivity, reduced internal traps, and enhanced charge transfer efficiency. The detectivity, spanning from 400 to 1100 nm, surpassed ∼5 × 10 12 Jones, reaching ∼1.1 × 10 12 Jones at 1000 nm, accompanied by an increased responsivity of 0.47 A/W. Also, the unpackaged OPD remarkedly demonstrated stable J D and external quantum efficiency (EQE) over 1000 h under dark storage conditions. This innovative approach not only addresses the drawbacks of conventional PEIE-based OPDs but also offers promising avenues for the development of high-performance OPDs in the future.

Perovskite solar cells (PSCs) have gained much attention in recent years because of their improved energy conversion efficiency, simple fabrication process, low processing temperature, flexibility, light weight, and low cost of constituent materials when compared with their counterpart silicon based solar cells. Besides, stability and toxicity of PSCs and low power conversion efficiency have been an obstacle towards commercialization of PSCs which has attracted intense research attention. In this research paper, a Glass/Cu 2 O/CH 3 NH 3 SnI 3 /ZnO/Al inverted device structure which is made of cheap inorganic materials, n-type transparent conducting oxide (TCO)-free, stable, photoexcited toxic-free perovskite have been carefully designed, simulated and optimized using a one-dimensional solar cell capacitance simulator (SCAPS-1D) software. The effects of layers' thickness, perovskite's doping concentration and back contact electrodes have been investigated, and the optimized structure produced an open circuit voltage (V oc ) of 1.0867 V, short circuit current density (J SC ) of 33.4942 mA/cm 2 , fill factor (FF) of 82.88% and power conversion efficiency (PCE) of 30.17%. This paper presents a model that is first of its kind where the highest PCE performance and eco-friendly n-type TCO-free inverted CH 3 NH 3 SnI 3 based perovskite solar cell is achieved using all-inorganic transport materials., (© 2024. The Author(s).)

Infrared (IR) solar cells, capable of converting low-energy IR photons to electron-hole pairs, are promising optoelectronic devices by broadening the utilization range of the solar spectrum to the short-wavelength IR region. The emerging PbS colloidal quantum dot (QD) IR solar cells attract much attention due to their tunable band gaps in the IR region, potential multiple exciton generation, and facile solution processing. In PbS QD solar cells, ZnO is commonly utilized as an electron transport layer (ETL) to establish a depleted heterostructure with a QD photoactive layer. However, band gap shrinkage of large PbS QDs makes it necessary to tailor the behaviors of the ZnO ETL for efficient carrier extraction in the devices. Herein, the characteristics of ZnO ETL are efficiently and flexibly tailored to match the QD layer by handily adjusting the postannealing process of ZnO ETL. With a suitable temperature, the well-matched energy level alignment and suppressed trap states are simultaneously achieved in the ZnO ETL, effectively reducing the nonradiative recombination and accelerating the electron injection from the QD layer to ETL. As a consequence, a high-performance PbS QD photovoltaic device with power conversion efficiencies (PCEs) of 10.09% and 1.37% is obtained under AM 1.5 and 1100 nm filtered solar illumination, demonstrating a simple and effective approach for achieving high-performance IR photoelectric devices.

At present, heavy-metal-free quantum dot light-emitting diodes (QLEDs) have shown great potential as a research hotspot in the field of optoelectronic devices. This article reviews the research on heavy-metal-free quantum dot (QD) materials and light-emitting diode (LED) devices. In the first section, we discussed the hazards of heavy-metal-containing quantum dots (QDs), such as environmental pollution and human health risks. Next, the main representatives of heavy-metal-free QDs were introduced, such as InP, ZnE (E=S, Se and Te), CuInS 2 , Ag 2 S, and so on. In the next section, we discussed the synthesis methods of heavy-metal-free QDs, including the hot injection (HI) method, the heat up (HU) method, the cation exchange (CE) method, the successful ionic layer adsorption and reaction (SILAR) method, and so on. Finally, important progress in the development of heavy-metal-free QLEDs was summarized in three aspects (QD emitter layer, hole transport layer, and electron transport layer).

Low-temperature processed electron transport layer (ETL) of TiO 2 that is widely used in planar perovskite solar cells (PSCs) has inherent low carrier mobility, resulting in insufficient photogenerated electron transport and thus recombination loss at buried interface. Herein, we demonstrate an effective strategy of laser embedding of p-n homojunctions in the TiO 2 ETL to accelerate electron transport in PSCs, through localized build-in electric fields that enables boosted electron mobility by two orders of magnitude. Such embedding is found significantly helpful for not only the enhanced crystallization quality of TiO 2 ETL, but the fabrication of perovskite films with larger-grain and the less-trap-states. The embedded p-n homojunction enables also the modulation of interfacial energy level between perovskite layers and ETLs, favoring for the reduced voltage deficit of PSCs. Benefiting from these merits, the formamidinium lead iodide (FAPbI 3 ) PSCs employing such ETLs deliver a champion efficiency of 25.50%, along with much-improved device stability under harsh conditions, i.e., maintain over 95% of their initial efficiency after operation at maximum power point under continuous heat and illumination for 500 h, as well as mixed-cation PSCs with a champion efficiency of 22.02% and over 3000 h of ambient storage under humidity stability of 40%. Present study offers new possibilities of regulating charge transport layers via p-n homojunction embedding for high performance optoelectronics., (© 2024. The Author(s).)

Context: Density functional theory (DFT) calculations are carried out on pure and doped rutile TiO 2 . The bandgap (E g ) for pristine, S-doped, Fe-doped, and Fe/S co-doped materials is direct, with values of 2.98 eV, 2.18 eV, 1.58 eV, and 1.40 eV. The effective mass of charge carriers (m*) and ratio of effective masses of holes to effective masses of electrons (R) are also investigated, and it is discovered that Fe/S co-doped materials have the lowest charge carrier recombination rate. The Fe/S co-doped material has the highest ε ( ω ) . α ( ω ) of doped materials shifted into the visible range. Due to the high dopant concentration in Fe and Fe/S-doped cases, the E g is lowered to a relatively small value; hence, only pristine and S-doped materials are verified as electron transport layer (ETL). A solar cell device analysis employing pure and S-doped rutile TiO 2 as ETL is completed using DFT-derived parameters in SCAPS-1D modeling software for the first time. For the optimized solar cells, current-voltage (IV) characteristics, quantum efficiency (QE), capacitance-voltage (CV) characteristics, and capacitance-frequency (Cf) characteristics are provided. The aim of the present study is to improve efficiency of perovskite solar cell by doping as well as to improve accuracy of simulation by applying DFT extracted parameters as input. From the analysis, improvement is found in efficiency of doped TiO 2 compared to un-doped TiO 2 . The efficiency of the PSC with S-doped ETL is 1.418% higher than the PSC with un-doped ETL., Method: Quantumwise Automistic Tool Kit (ATK) is used to extract DFT parameters. Using these DFT parameters as input in SCAPS-1D (Solar Cell Capacitance Simulator), solar cells for doped and un-doped material are simulated. The density functional theory (DFT)-based orthogonalized linear combination of atomic orbital (OLCAO) technique is used. Structural optimization is done using the LBFGS (Limited-memory Broyden-Fletcher-Goldfarb-Shanno). PBESol-GGA (Perdew-Burke-Ernzerhof solid-generalized gradient approximation) is applied as exchange correlation for calculating structural parameters, while MGGA-TB09 (meta-generalized gradient approximation-Tran and Blaha) is applied as exchange correlation for calculating optical and electronic properties., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The solution-processed zinc oxide (ZnO) electron transport layer (ETL) always exhibits ubiquitous defects, and its photocatalytic activity is detrimental for the organic solar cell (OSC) to achieve high efficiency and stability. Herein, an organic dye molecule, PDINN-S is introduced, to dope ZnO, constructing a hybrid ZnO:PDINN-S ETL. This hybrid ETL exhibits improved electron mobility and conductivity, particularly post-light exposure. The catalytic activity of ZnO is also effectively suppressed.Consequently, the efficiency and photo-stability of inverted non-fullerene OSCs are synergistically enhanced. The devices based on PM6:Y6/PM6:BTP-eC9 active layer with ZnO:PDINN-S as ETL give impressive power conversion efficiencies (PCEs) of 16.78%/17.59%, significantly higher than those with pure ZnO as ETL (PCEs = 15.31%/16.04%). Moreover, ZnO:PDINN-S-based device shows exceptional long-term stability under continuous AM 1.5G illumination (T 80 = 1130 h) , overwhelming the reference device (T 80 = 455 h). In addition, Incorporating PDINN-S into ZnO alleviate mechanical stress within the inorganic lattice, making ZnO:PDINN-S ETL more suitable for the fabrication of flexible devices. Overall, doping ZnO with organic dye molecules offers an innovative strategy for developing multifunctional and efficient hybrid ETL of the non-fullerene OSCs with excellent efficiency and photo-stability., (© 2023 Wiley‐VCH GmbH.)