Spectroscopic Perception of Trap States on the Performance of Methylammonium and Formamidinium Lead Iodide Perovskite Solar Cells

To enhance the efficiency and stability of the organic-inorganic hybrid perovskite (OIHP) solar cells, doping has been demonstrated as a straightforward method. Nevertheless, the perception of trap states regulated by doping and their effects on the performance of solar cells is not in-depth. Herein, typical OIHPs (CH₃ NH₃ PbI₃ and Cs_0.05 FA_0.85 MA_0.10 Pb(I_0.97 Br_0.03 )₃ ) doped with RbI are employed to expound the doping mechanism in affecting the efficiency of devices. Systematic spectroscopic characterizations indicate that doping significantly influences the photocarrier dynamics via directly regulating the trap states. The results indicate that doping would reduce the trap density by passivating defects and induce extra trapping centers. This directly manipulates the transient transport of the photocarriers and finally influences the output of devices. The optimization of solar cell performance requires the tradeoff of competitive relation between the passivation and introduction of trapping centers. The results provide the spectroscopic perception on how doping concentration affects trap density, carrier dynamics, transport behavior, and ultimately the parameters of devices. It provides a straightforward guidance to the design and optimization of OIHP-based solar cells.