Passivation of defects in perovskite solar cell: From a chemistry point of view

A certified 25.2% efficiency of metal halide perovskite solar cells (PSCs) has been rapidly reached in 2019 within just a decade which is unprecedented in the field of photovoltaics. Excellent optoelectronic properties such as high absorption coefficient, tunable direct bandgap, long diffusion length, and high carrier mobility promise a further improvement of device performance. However, as a result of the solution precursor compositions and rapid processing conditions, tremendous amounts of defects with various types are formed within perovskite absorbers or on the surfaces, which serve as the nonradiative recombination centers to impede the rapid development of PSCs. Therefore, learned from the field of mature Silicon-based solar cell, passivation of such defects in the bulk and/or at the surface, as well as influence the interface tuning of structure and energetics has to be urgently conducted by choosing appropriate chemical molecules, which have the potential of tailoring crystallization and growth of perovskite absorbers. Here, recent advances in passivation engineering for perovskite film formation or interface optimization are summarized and discussed according to the following typical categories: Lewis acid (e.g., metal cations, organic cations, zwitterion, fullerene derivatives), Lewis base based on the donor type (e.g., anions, S-donor, N-donor, O-donor, graphene derivatives, and n-π conjugated materials), passivators with multifunctional groups. Finally, a perspective is predicted on future research trends concerning passivation engineering in advancing the development of PSCs, especially in efficiency, stability, and commercialization.