Dual Role of Rapid Transport and Efficient Passivation in Inverted Methylammonium-Free Perovskite Solar Cells Utilizing a Self-Assembled Porous Insulating Layer

In recent years, the surface modification of perovskite by wide band-gap insulating materials has been one of the main strategies to achieve efficient and stable perovskite solar cells (PSCs). Unfortunately, a significant hurdle in this approach is the dilemma surrounding the quality of passivation and the transport of charges. Here, this trade-off is overcome by introducing self-assembled diphenylphosphinic acid (DPPA) porous layer. Applying highly concentrated DPPA solution on the perovskite surface not only provides excellent passivation of entire surface, but also the excess DPPA will form a self-assembled porous insulating layer (PIL), which forms random submicron-sized openings at the interface of the insulating layer for accelerated charge transport. In addition, the energy level of the perovskite surface can be modulated by this insulating material to facilitate carrier transport. As a result, an impressive power conversion efficiency (PCE) over 24% has been achieved in methylammonium-free p-i-n devices with an ultrahigh fill factor (FF) of 84.7%. The unencapsulated devices exhibit excellent thermal and operational stability. This work paves a way for establishment of an effective passivation and facilitated transport simultaneously. A porous insulating layer (PIL) made of self-assembled diphenylphosphinic acid (DPPA) is fabricated atop a perovskite film to address the challenge of balancing defect passivation and charge transport. Entire surface of perovskite film is well-passivated and energy level is modulated with DPPA treatment, and surplus DPPA forms PIL with submicrometer-scale openings, providing efficient charge transport pathways. The methylammonium-free perovskite devices with PIL structures exhibit enhanced efficiency and operational stability.image