Low‐Bandgap Organic Bulk‐Heterojunction Enabled Efficient and Flexible Perovskite Solar Cells

Lead halide perovskite and organic solar cells (PSCs and OSCs) are considered as the prime candidates currently for clean energy applications due to their solution and low‐temperature processibility. Nevertheless, the substantial photon loss in near‐infrared (NIR) region and relatively large photovoltage deficit need to be improved to enable their uses in high‐performance solar cells. To mitigate these disadvantages, low‐bandgap organic bulk‐heterojunction (BHJ) layer into inverted PSCs to construct facile hybrid solar cells (HSCs) is integrated. By optimizing the BHJ components, an excellent power conversion efficiency (PCE) of 23.80%, with a decent open‐circuit voltage (Voc) of 1.146 V and extended photoresponse over 950 nm for rigid HSCs is achieved. The resultant devices also exhibit superior long‐term (over 1000 h) ambient‐ and photostability compared to those from single‐component PSCs and OSCs. More importantly, a champion PCE of 21.73% and excellent mechanical durability can also be achieved in flexible HSCs, which is the highest efficiency reported for flexible solar cells to date. Taking advantage of these impressive device performances, flexible HSCs into a power source for wearable sensors to demonstrate real‐time temperature monitoring are successfully integrated. A flexible hybrid solar cell with extended photoresponse, high power conversion efficiency of 21.73%, and excellent mechanical durability is realized by incorporating a low‐bandgap organic bulk heterojunction layer into perovskite solar cells. Taking advantage of these impressive device performance, the flexible solar cell–sensor integrated system is demonstrated for real‐time temperature monitoring via on‐body evaluation.