The band bending effect of LiI/NaI treated TiO2 photoanodes on the performance of dye-sensitized solar cells.

A new method has been developed for surface treatment of TiO2 photoanodes with LiI/NaI to enhance the photocurrent and, subsequently, the performance efficiency of the fabricated dye-sensitized solar cells (DSSCs). Three different concentrations (0.1, 0.25, and 0.5 mmol%) of LiI and NaI solutions were used to investigate the effect of this surface treatment on the device performance of DSSCs. A positive shift in the energy level of TiO2 has been experienced by surface treated devices, which is predominantly supported by the decrease in VOC. Furthermore, the introduction of LiI/NaI onto the TiO2 surface resulted in a reduction in the crystallite size, indicating an increase in the surface area which helps in more dye adsorption leading to higher JSC values of the devices. Besides, modification of the conduction band energy level, it also allows a fast electron injection process by shifting the density of states. Thus, this approach offers a simple but efficient route to enhance the photocurrent and efficiency of DSSCs.

LARP-assisted synthesis of CsBi3I10 perovskite for efficient lead-free solar cells.

Bismuth-based perovskites are an important class of materials in the fabrication of lead-free perovskite solar cells. Bi-based Cs3Bi2I9 and CsBi3I10 perovskites are getting much attention due to their appropriate bandgap values of 2.05 eV and 1.77 eV, respectively. However, the device optimisation process plays a key role in controlling the film quality and the performance of perovskite solar cells. Hence, a new strategy to improve crystallization as well as the thin film quality is equally important to develop efficient perovskite solar cells. Herein, an attempt was made to prepare the Bi-based Cs3Bi2I9 and CsBi3I10 perovskites via the ligand-assisted re-precipitation approach (LARP). The physical, structural, and optical properties were investigated on perovskite films deposited by the solution process for solar cell applications. Cs3Bi2I9 and CsBi3I10-based perovskite-based solar cells were fabricated using the device architecture of ITO/NiO x /perovskite layer/PC61BM/BCP/Ag. The device fabricated with CsBi3I10 showed the best power conversion efficiency (PCE) of 2.3% with an improved fill factor (FF) of 69%, V OC of 0.79 V, and J SC of 4.2 mA cm-2 compared to the Cs3Bi2I9-based device which showed a PCE of 0.7% with a FF of 47%, V OC of 0.62 V and J SC of 2.4 mA cm-2.