Fabrication and characterization of mixed lead halide thin films for perovskite solar cells

Abstract

Recently, a new class of perovskite was introduced as a light harvesting material that shows strong absorption in a broad region of the visible spectrum, good electron and hole conductivity, and delivers high open circuit voltages in photovoltaic devices. Perovskite solar cells consist of CH3NH3PbX3 loaded on a mesoporous TiO2 layer in conjunction with the hole transporting material between the two electrodes. Optimizing the efficiency of perovskite solar cells is important for light harvesting devices. One approach to improving the efficiency is to increase the charge collection; the electron diffusion length and recombination lifetime influence the performance of perovskite solar cells. In this study, the influence of PbCl2 content in a PbI2 solution of N, N-dimethylformamide (DMF) on the absorption, crystal phase, and morphology of lead halide thin films was systematically investigated and the photovoltaic performance of the corresponding planar perovskite solar cells was evaluated. The planar perovskite solar cell based on the 300-nm-thick methyl ammonium iodide (CH3NH3I):PbI2:PbCl2 (4 M:1.25 M:0.75 M) thin film exhibited the optimum photoelectric conversion efficiency of 6.3% along with an open-circuit voltage of 0.66 V, a short-circuit photocurrent density of 19.60 mA cm(-2), and a fill factor of 58.3%.