Efficient and stable flexible perovskite solar cells based on graphene-AgNWs substrate and carbon electrode without hole transport materials

Carbon electrode-based hole transport layer-free perovskite solar cells (C–PSCs) are widely recognized as a competitive candidate towards practical applications, due to their advantages of low-cost, easy-fabrication, and long-term stability. However, fully low-temperature preparation of this type of solar cells on flexible substrates remains a huge challenge. Here, the all carbon electrode-based flexible C–PSCs with the structure of polyethylene terephthalate (PET)/graphene-silver nanowires (graphene–AgNWs)/SnO2/CH3NH3PbI3/Carbon are successfully prepared by low-temperature solution process. By optimizing the fabrication condition, an optimal efficiency of 9.73% is obtained, which is the highest value reported so far for flexible C–PSCs. Meanwhile, these flexible devices demonstrate superior mechanical robustness in comparison with their counterparts fabricated on flexible indium tin oxide (ITO)/PET substrates as well as excellent long-term durability. The present study can provide a simple way to fabricate low cost, highly efficient and highly stable perovskite solar cells for various applications.