Microwave-facilitated crystal growth of defect-passivated triple-cation metal halide perovskites toward efficient solar cells

Structural defects at the surface and within the bulk of perovskite films hinder efficient energy conversion in solar cells due to the loss of charge carriers through non-radiative recombination. Post-passivation approaches have been proposed in an attempt to eliminate surface defects, with bulk defects being rarely studied. Moreover, it is of interest to investigate the difference in the perovskite crystal growth with and without simultaneous defect passivation. Here, we study a new crystal growth strategy to realize high-quality triple-cation perovskite crystals via utilizing microwave irradiation combined with a continuous supply of defect passivators from a reservoir solution of trioctyl-n-phosphine oxide (TOPO). The proposed method facilitates the growth of perovskite crystals with TOPO ligand coordination in the whole film region. Consequently, the processed perovskite film demonstrates distinctive features of significantly suppressed non-radiative recombination, substantial defect reduction and morphological changes compared to the perovskites processed by conventional thermal annealing. The power conversion efficiency is enhanced owing to the improved open-circuit voltage (V_oc) and short-circuit current (J_sc). The results of this study are expected to assist in the development of diverse approaches for the control of perovskite crystal growth with in situ defect passivation toward high efficiency in solar cells.