Flexible and Biocompatibility Power Source for Electronics: A Cellulose Paper Based Hole‐Transport‐Materials‐Free Perovskite Solar Cell

Flexible, biocompatible, and light‐weight power sources are urgently required due to their promising application in wearable electronics. Organic‐inorganic hybrid lead halide perovskite solar cells (PSCs) with their impressive efficiency and scalable processing capability have emerged as promising candidates for efficient and reliable power sources for wearable electronics. However, the progress in developing low‐cost and efficient flexible PSCs has been confined to Poly(ethylene terephthalate) or metal foil substrates and difficulty to design PSCs on other easily accessible low‐cost substrates such as cellulose paper. Herein, the authors report the hole transport material (HTM)‐free flexible PSCs fabricated on abundant, low‐cost, and biocompatible cellulose paper substrate for the first time. The highest PCE of 9.05% for the paper based flexible HTM‐free PSC is achieved and the device could maintain over 75% of its initial PCE after 1000 bending cycles, demonstrating good stability against bending deformation. Our findings provide an avenue to fabricate reliable power source for wearable electronics.