Stable and Highly Flexible Perovskite Solar Cells with Power Conversion Efficiency Approaching 20% by Elastic Grain Boundary Encapsulation

Here, we show that flexible perovskite solar cells (PSCs) with high operational stability and power conversion efficiency (PCE) approaching 20% were achieved by elastic grain boundary (GB) encapsulation. An introduction of trimethyltrivinylcyclotrisiloxane (V3D3) and solvent annealing (SA) resulted in an in situ cross-linking reaction between GBs and enlarged grain size that enabled oriented charge-transport properties to be achieved synchronously, leading to reduced sheet resistance with a high fill factor (FF) up to 82.93% in flexible PSCs. Meanwhile, the insulating elastic V3D3 for GB encapsulation suppressed the carrier recombination substantially, as well as ion migration, which enhanced both the mechanical and the operational stability dramatically in flexible PSCs. Additionally, more than 73% of its initial PCE was retained even after 10,000 bending cycles, with 83% of its stabilized PCE remaining after 300 h of continuous operation at maximum power point (MPP) condition under one sun illumination without cooling.