Emerging Trends in Electron Transport Layer Development for Stable and Efficient Perovskite Solar Cells.

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 TiO2, ZnO, SnO2, 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.

Process Accumulated 8% Efficient Cu2 ZnSnS4 -BiVO4 Tandem Cell for Solar Hydrogen Evolution with the Dynamic Balance of Solar Energy Storage and Conversion.

A process accumulated record solar to hydrogen (STH) conversion efficiency of 8% is achieved on the Cu2 ZnSnS4 -BiVO4 tandem cell by the synergistic coupling effect of solar thermal and photoelectrochemical (PEC) water splitting with the dynamic balance of solar energy storage and conversion of the greenhouse system. This is the first report of a Cu2 ZnSnS4 -BiVO4 tandem cell with a high unbiased STH efficiency of over 8% for solar water splitting due to the greenhouse device system. The greenhouse acts as a solar thermal energy storage cell, which absorbs infrared solar light and storage as thermal energy with the solar light illumination time, while thermoelectric device (TD) converts thermal energy into electric power, electric power is also recycled and added onto Cu2 ZnSnS4 -BiVO4 tandem cell for enhanced overall water splitting. Finally, the solar water splitting properties of the TD-Cu2 ZnSnS4 -BiVO4 integrated tandem cell in pure natural seawater are demonstrated, and a champion STH efficiency of 2.46% is presented, while a large area (25 cm2 ) TD-Cu2 ZnSnS4 -BiVO4 integrated tandem device with superior long-term stability is investigated for 1 week, which provides new insight into photoelectrochemical solar water splitting devices.

Effects of working pressure on the material and defect properties of Sb2S3 thin-film solar cells achieved by the VTD method.

Antimony sulfide (Sb2S3), an emerging material for photovoltaic devices, has drawn growing research interest due to its inexpensive and high-throughput device production. In this study, the material and defect properties of Sb2S3 thin films prepared by the vapor transport deposition (VTD) method at different working pressures were studied. Solar cells based on a structure of glass/ITO/CdS/Sb2S3/Au were fabricated. The working pressure showed a significant effect on the device's performance. The current density versus voltage measurement and scanning electron microscopy analysis outcome were utilized to investigate the photovoltaic and microstructural properties in the samples. The compositional analysis by energy dispersive X-ray spectroscopy measurement confirmed the Sb/S ratio as 2:2.8 for the thin films. The identification and characterization of the defects present in Sb2S3 thin films were performed via admittance measurements. Compared to the defect density, the defect energy level was found to inherit a more important role in the device's performance. The best solar cell performance with better crystal quality, lower defect density, and longer capture lifetime was achieved under the substrate working pressure of 2 Pa. The highest efficiency was found to be 0.86% with Voc=0.55V, Jsc=5.07mA/cm2.

Effects of Copper Dopants on the Magnetic Property of Lightly Cu-Doped ZnO Nanocrystals.

To explore the origin of magnetism, the effect of light Cu-doping on ferromagnetic and photoluminescence properties of ZnO nanocrystals was investigated. These Cu-doped ZnO nanocrystals were prepared using a facile solution method. The Cu2+ and Cu+ ions were incorporated into Zn sites, as revealed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). At the Cu concentration of 0.25 at.%, the saturated magnetization reached the maximum and then decreased with increasing Cu concentration. With increasing Cu concentration, the photoluminescence (PL) spectroscopy indicated the distribution of VO+ and VO++ vacancies nearly unchanged. These results indicate that Cu ions can enhance the long-range ferromagnetic ordering at an ultralow concentration, but antiferromagnetic "Cu+-Vo-Cu2+" couples may also be generated, even at a very low Cu-doping concentration.

Effects of working pressure and power on photovoltaic and defect properties of magnetron sputtered Sb2Se3 thin-film solar cells.

Antimony selenide (${\text{Sb}_2}{\text{Se}_3}$Sb2Se3) is an emerging material with potential applications in photovoltaics, while magnetron sputtering is an important method in material growth. In this study, ${\text{Sb}_2}{\text{Se}_3}$Sb2Se3 thin films, prepared by the magnetron sputtering technique with varied working pressures and sputtering powers, were fabricated into solar cells with a structure of $\text{glass}/\text{ITO}/\text{CdS}/{\text{Sb}_2}{\text{Se}_3}/\text{Au}$glass/ITO/CdS/Sb2Se3/Au. The current density versus voltage measurements and x-ray diffraction were introduced to compare the photovoltaic and structural properties of the cell samples. Characterization and identification of the defects in ${\text{Sb}_2}{\text{Se}_3}$Sb2Se3 thin films were investigated by admittance measurements. The ${\text{Sb}_2}{\text{Se}_3}$Sb2Se3 cell samples prepared with appropriate sputtering power (about 60 W) or working pressure (about 0.4 Pa) were found to own better crystal qualities and lower defect densities, which may be the reason for better efficiency.

Effects of substrate temperature on material and photovoltaic properties of magnetron-sputtered Sb2Se3 thin films.

We studied the material and photovoltaic properties of Sb2Se3 thin films fabricated by a magnetron-sputtering method at different substrate temperatures. The films had good crystallinity at substrate temperatures over 300°C. The band-gap energies between 1.1 and 1.5 eV of the films, which were obtained by transmittance measurements, initially decreased and then increased slowly with increasing temperature. Solar cells based on the films with structures of ITO/CdS/Sb2Se3/Au were fabricated, and the substrate temperature had significant effects on the device performance. Low crystal quality at low temperature resulted in a low short-circuit current (Jsc), while high temperature caused Se deficiency due to evaporation, which decreased the open-circuit voltage (Voc). The best solar cell performance achieved an efficiency of 0.84% with a Voc of 0.27 V and Jsc of 9.47 mA/cm2 when the substrate temperature was 325°C.

Efficient and Hole-Transporting-Layer-Free CsPbI2 Br Planar Heterojunction Perovskite Solar Cells through Rubidium Passivation.

Recently, inorganic perovskite CsPbI2 Br has gained much attention for photovoltaic applications owing to its excellent thermal stability. However, low device performance and high open-voltage loss, which are the result of its intrinsic trap states, are hindering its progress. Herein, planar CsPbI2 Br solar cells with enhanced performance and stability were demonstrated by incorporating rubidium (Rb) cations. The Rb-doped CsPbI2 Br film exhibited excellent crystallinity, pinhole-free surface morphology, and enhanced optical absorbance. By using low-cost carbon electrodes to replace the organic hole-transportation layer and metal electrode, an excellent efficiency of 12 % was achieved with a stabilized efficiency of over 11 % owing to the suppressed trap states and recombination in the CsPbI2 Br film. Additionally, the annealing temperature for the Rb-doped CsPbI2 Br film could be as low as 150 °C with a comparable high efficiency over 11 %, which is one of the best efficiencies reported for hole-transporting-layer-free all-inorganic perovskite solar cells. These results could provide new opportunities for high-performance and stable inorganic CsPbI2 Br solar cells by employing A-site cation substitution.

A sputtered CdS buffer layer for co-electrodeposited Cu2ZnSnS4 solar cells with 6.6% efficiency.

Cu2ZnSnS4 thin films with thicknesses ranging from 0.35 to 1.85 µm and micron-sized grains (0.5-1.5 µm) were synthesized using co-electrodeposited Cu-Zn-Sn-S precursors with different deposition times. Here we have introduced a sputtered CdS buffer layer for the development of CZTS solar cells for the first time, which enables breakthrough efficiencies up to 6.6%.