Improving perovskite solar cell performance by compositional engineering via triple-mixed cations

Compositional engineering with the addition of organic and inorganic cations is regarded as an effective way to improve the performance of perovskite solar cells (PSCs). However, exploration of triple-mixed cations in PSCs is still in its initial stage. In this study, triple cations of MA⁺, FA⁺, and Gua⁺ are mixed into perovskite and moulded into a 3D structure by the two-step deposition method, thus proving the feasibility of the triple-cation-based perovskite layer. Through the results of X-ray diffraction (XRD), scanning electron microscope (SEM), and Photoluminescence (PL) tests, Gua_y(FAMA)_1-yPbI_xCl_3-x perovskite crystallisation was observed. The triple-mixed, cation-based perovskite film exhibits improved crystal quality, larger grain size, and fewer trap densities, all of which are positive for final power conversion efficiency (PCE) and stability. Based on the optimised MA⁺ and FA⁺ component ratio, the PSC showed the best performance with a GuaI doping concentration of 10%. The introduction of GuaI further improves the performance of devices by the passivation of defects and suppression of nonradiative recombination. The final PSCs displayed the best PCE (21.3%), as well as enhanced stability.