The film quality of the electron transport layer (ETL) plays an important role in improving the performance of perovskite solar cells (PSCs). In order to reduce the effect of rough fluorine-doped SnO₂ (FTO)substrate on the film quality of the TiO₂ ETL, multiple cycles of spin-coating were employed to realize optimized TiO₂ film and improve the performance of PSCs with rough FTO. The results show that TiO₂ ETL was optimized most effectively using two spin-coating cycles, obtaining the best performance of PSCs with rough FTO. The carbon electrode-based PSCs were then demonstrated. Our work discusses the feasibility of low-quality rough FTO for the fabrication of PSCs and photodetectors to reduce costs.

In recent years, flexible perovskite solar cells have drawn tremendous attention in the field of wearable devices, and optimization of perovskite composition plays an important role in improving film quality and photophysical properties. At present, some researchers have only studied A-site organic cations mixing or X-site halide anions mixing in the ABX₃ structure of perovskite, but there are few reports on co-mixing of A-site and X-site ions in flexible perovskite solar cells. In this paper, we mainly try to study the effects of different concentrations of mixed formamidine methylamine halide (FA_xMA_1-xBr_xCl_yI_1-x-y) precursor solutions on the quality and photophysical properties of perovskite films under low temperature process. We conclude that the film quality and photophysical properties reached the best results when the optimized precursor solution concentration was 60:6:6. The investigation on composition optimization in this experiment laid the foundation for the improvement of the performance of flexible perovskite solar cells. We also use the results of this experiment to prepare flexible perovskite solar cells based on carbon electrodes, which are expected to be applied in other flexible optoelectronic or electro-optical devices.

Flexible perovskite solar cells (PSCs) have received increasing attention in wearable and portable devices over the past ten years. The low-temperature process of electron transport layer plays a key role in fabricating flexible PSCs. In this paper, we improve the performance of flexible PSCs by controlling the thermodynamic procedure in the low-temperature annealing process of solution-processed TiO₂ layers and modulating the precursor concentration of (6,6)-phenyl c₆₁ butyric acid methyl ester (PC₆₁BM) deposited on fluorine-doped tin oxide (FTO)/TiO₂ substrate. The results show that slowing down evaporation rate of residual solvent and adopting PC₆₁BM of appropriate precursor concentration are confirmed to be effective methods to improve the performance of flexible PSCs. We also demonstrate carbon electrode-based flexible PSCs. Our work expands the feasibility of low temperature process for the development of flexible perovskite photodetectors and light-emitting diodes, as well as flexible PSCs.

The investigation of crystal growth is crucial for us to improve the film quality and photophysical properties of CH₃NH₃PbI₃ (MAPbI₃). In the two-step spin-coating process, the crystal structure could be modulated by controlling the growth conditions of PbI₂ and CH₃NH₃I (MAI) layers. In this paper, the PbI₂ layer was treated with annealing under different times. A liquid–liquid diffusion (LLD) mechanism is proposed to modify the deposition of MAI precursor solution and enhance the flatness of organic–inorganic hybrid perovskite film. Furthermore, the perovskite films are prepared using different concentrations of MAI. The evolution process of perovskite structure is observed by modulating the concentration of MAI. The spin-coating of moderate MAI tends to form high quality MAPbI₃ films with enhanced absorption and carrier extraction capabilities. The high concentration of MAI would cause the perovskite phase transition, which provides a novel perspective to modulate the structure of organic–inorganic hybrid perovskite in the two-step spin-coating process, although it deteriorates the device performance.

With the development of the semiconductor industry, research on photoelectronic devices has been emphasized. In this paper, a molecular semiconductor material with a narrow bandgap of hexane-1,6-diammonium pentaiodobismuth (HDA-BiI₅) was utilized to prepare photodetectors without electron transport layers. Using a single light source, the effects of different wavelengths and different powers on the photoresponsivity, switching ratio, specific detectivity, and external quantum efficiency of the device were investigated. It is demonstrated that this device has excellent responsivity, specific detectivity, stability, and repeatability, and this work will help expand the application of molecular semiconductor materials for photodetection.

Photoelectric devices can be so widely used in various detection industries that people began to focus on its research. The research of photoelectric sensors with high performance has become an industry goal. In this paper, we prepared photodetectors using organic–inorganic hybrid semiconductor materials with narrow bandgap hexane-1,6-diammonium pentaiodobismuth (HDA-BiI₅) and investigated the detector photoresponse and time-response characteristics under a single light source. The device exhibits high photoresponsivity and fast response time. The photoresponsivity can reach 1.45 × 10⁻³ A/W and 8.5 × 10⁻⁴ A/W under laser irradiation at 375 nm and 532 nm wavelengths, and the rise and decay times are 63 ms and 62 ms, 62 ms and 64 ms, respectively. The device has excellent performance and this work can extend the application of organic–inorganic hybrid semiconductor materials in photovoltaic and photodetectors.