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NiOx-based inverted perovskite solar cells (PSCs) have presented great potential toward low-cost, highly efficient and stable next-generation photovoltaics. However, the presence of energy-level mismatch and contact-interface defects between hole-selective contacts (HSCs) and perovskite-active layer (PAL) still limits device efficiency improvement. Here, we report a graded configuration based on both interface-cascaded structures and p-type molecule-doped composites with two-/three-dimensional formamidinium-based triple-halide perovskites. We find that the interface defects-induced non-radiative recombination presented at HSCs/PAL interfaces is remarkably suppressed because of efficient hole extraction and transport. Moreover, a strong chemical interaction, halogen bonding and coordination bonding are found in the molecule-doped perovskite composites, which significantly suppress the formation of halide vacancy and parasitic metallic lead. As a result, NiOx-based inverted PSCs present a power-conversion-efficiency over 23% with a high fill factor of 0.84 and open-circuit voltage of 1.162 V, which are comparable to the best reported around 1.56-electron volt bandgap perovskites. Furthermore, devices with encapsulation present high operational stability over 1,200 h during T90 lifetime measurement (the time as a function of PCE decreases to 90% of its initial value) under 1-sun illumination in ambient-air conditions.

The use of transparent conducting oxide (TCO) as a substrate in Cu2ZnSn(S,Se)4 (CZTSSe) thin-film solar cells allows for advanced applications, such as bifacial, semi-transparent, and tandem solar cells with the capability to increase power density generation. However, the efficiency of this kind of solar cell is still below 6% based on the low-cost solution process. In this work, we develop a composition gradient strategy and demonstrate a 6.82% efficient CZTSSe solar cell on F:SnO2 (FTO) substrate under the ambient condition. The composition gradient is realized by simply depositing the precursor inks with different Zn/Sn ratios. To verify that the high performance of the solar cell is attributed to the composition gradient strategy rather than the sole change of the Zn/Sn ratio, devices based on absorbers with varied Zn/Sn ratios are fabricated. Furthermore, the structure and surface morphology of the CZTSSe films with/without composition gradients are examined. The presence of elemental gradient through the depth of the CZTSSe films before and after annealing is confirmed by secondary ion mass spectroscopy analysis. It is found that the composition gradient enhances the crystallinity of the absorber, reduces the surface roughness as well as device parasitic losses, contributing to a higher fill factor, open-circuit voltage and conversion efficiency.

Defects located at the surfaces and grain boundaries of solution-processed perovskite films serve as nonradiative recombination centers and are detrimental for the photovoltaic performance of solar devices. Herein, a natural amino acid molecule methionine (Met) is selected as an effective passivation agent to enhance the optoelectronic properties of methylammonium lead iodide (MAPbI3) films. The incorporation of a small amount of Met significantly reduces the trap-state density, contributing to longer carrier lifetime of the perovskite films. As a result, solar cells made of Met-mediated perovskite films deliver a high photovoltage of 1.145 V, which is up to 100 mV higher than the control device. In addition, the Met-mediated device exhibits enhanced stability due to the reduced trap states and the improved hydrophobic property of the modified perovskite film, which retains ~ 85% of their initial efficiency after 480-h storage. The effective methionine passivation is reported, which significantly reduces the trap-state density and leads to longer carrier lifetime of the perovskite films. Methionine-mediated device produces a champion efficiency of 20.13%, with enhanced moisture stability.

Crystallization of glass/Aluminum (50, 100, 200 nm) /hydrogenated amorphous silicon (a-Si:H) (50, 100, 200 nm) samples by Aluminum-induced crystallization (AIC) is investigated in this article. After annealing and wet etching, we found that the continuity of the polycrystalline silicon (poly-Si) thin films was strongly dependent on the double layer thicknesses. Increasing the a-Si:H/Al layer thickness ratio would improve the film microcosmic continuity. However, too thick Si layer might cause convex or peeling off during annealing. Scanning electron microscopy (SEM) and Energy Dispersive X-ray spectroscopy (EDX) are introduced to analyze the process of the peeling off. When the thickness ratio of a-Si:H/Al layer is around 1 to 1.5 and a-Si:H layer is less than 200 nm, the poly-Si film has a good continuity. Hall measurements are introduced to determine the electrical properties. Raman spectroscopy and X-ray diffraction (XRD) results show that the poly-Si film is completely crystallized and has a preferential (111) orientation.

Antimony selenide (Sb2Se3) thin films were deposited by RF magnetron sputtering using a stoichiometric binary target onto the FTO glass substrates with various working pressures ranging from 0.3 to 10 Pa at room temperature and annealed at 300 °C in inert atmosphere. It was observed that the morphologies and microstructure were strongly affected by the working pressure. The Sb2Se3 thin films had [hk0] orientation preference at 0.3 Pa and 2 Pa, while the films were found to be easier to grow inclined to [hk1] direction at 5 Pa, 8 Pa, and 10 Pa in this work. As expected, the samples deposited at higher pressures exhibited better conductivity and the highest photocurrent reached about 580 μA when illuminated by a white LED with a power density of 5 mW cm−2. The Se losses were observed both during the sputtering and annealing processes. The solar cells were fabricated with a superstrate structure and the defects in the sputtered Sb2Se3 absorbers were analyzed.

In this work, n-type amorphous silicon oxide thin films were deposited by RF-PECVD method using a gas mixture of SiH4, CO2, H2, and PH3. The deposition rate, refractive index, band gap, crystalline volume fraction, and conductivity of the silicon oxide thin films were determined and analyzed. The film with refractive index of 1.99, band gap of 2.6eV and conductivity of 10−7 S/cm was obtained, which was suitable for the intermediate reflector layer.

Despite organometal halide perovskite solar cells have recently exhibited a significant leap in efficiency, the Sn-based perovskite solar cells still suffer from low efficiency. Here, a series homogeneous CH3NH3Pb(1−x)SnxI3 (0 ≤ x ≤ 1) perovskite thin films with full coverage were obtained via solvent engineering. In particular, the intermediate complexes of PbI2/(SnI2)∙(DMSO)x were proved to retard the crystallization of CH3NH3SnI3, thus allowing the realization of high quality Sn-introduced perovskite thin films. The external quantum efficiency (EQE) of as-prepared solar cells were demonstrated to extend a broad absorption minimum over 50% in the wavelength range from 350 to 950 nm accompanied by a noteworthy absorption onset up to 1050 nm. The CH3NH3Pb0.75Sn0.25I3 perovskite solar cells with inverted structure were consequently realized with maximum power conversion efficiency (PCE) of 14.12%.

Kesterite Cu2ZnSnS4 (CZTS) semiconductor has been demonstrated to be a promising alternative absorber in thin film solar cell in virtue of its earth-abundant, non-toxic element, suitable optical and electrical properties. Herein, a low-cost and non-toxic method that based on the thermal decomposition and reaction of metal-thiourea-oxygen sol-gel complexes to synthesize CZTS thin film was developed. The low-dimensional ZnO@CdS heterojunction nano-arrays coupling with the as-prepared CZTS thin film were employed to fabricate a novel solar cell with inverted structure. The vertically aligned nanowires (NWs) allow facilitating the charge carrier collection/separation/transfer with large interface areas. By optimizing the parameters including the annealing temperature of CZTS absorber, the thickness of CdS buffer layer and the morphology of ZnO NWs, an open-circuit voltage (VOC) as high as 589 mV was obtained by such solar cell with inverted structure. The all-solution-processed technic allows the realization of CZTS solar cell with extremely low cost.

Microcrystalline silicon with properties relevant to highly efficient solar cells can be suc-cessfully prepared on glass for material characterization if a thin intrinsic ‘seed layer’ coating of the substrate is used. This is demonstrated by a detailed structure analysis on the base of Raman spectroscopy and photothermal deflection spectroscopy. The coating turns out to be crucial (1) for achieving a crystalline content as high as that of solar cell absorber material, (2) for creating a homogeneous structure in growth direction, and (3) for extending the range of deposition pa-rameters which lead to films with high crystallinity towards the regime of amorphous growth. Regarding electrical transport, ‘seed layer’ assisted growth results in a structure dependence of the dark conductivity which is very similar to that of material grown on bare glass. Regarding optical absorption spectra, residual interference fringes, which indicate structure non-uniformities, are clearly suppressed by means of ‘seed layers’. It is concluded that appropriate ‘seed layers’ play an important role for a comprehensive characterization and development of microcrystalline silicon layers for thin film devices.