Dual-functional light-emitting perovskite solar cells enabled by soft-covered annealing process

Solution-processable perovskite semiconductors have demonstrated excellent performance in both perovskite solar cells (PeSCs)and perovskite light emitting diodes (PeLEDs). Their low exciton binding energy and excellent charge transport properties allow the conversion of photons into free electrons and holes and vice versa with minimal energy loss. In addition, planar PeSCs and PeLEDs have similar device architecture. These aspects inspired us to fabricate a dual-functional device with both SC and LED functions, here termed a light-emitting perovskite solar cells (LEPeSCs). However, the absence of an effective fabrication method to control grain size, uniformity, grain boundaries, and coverage of perovskite film inevitably limits device performance of dual-functional LEPeSCs. Here, we have demonstrated an efficient dual-functional LEPeSCs with planar device configuration of ITO/PEDOT:PSS/CH₃NH₃PbBrI₂/PC₆₁BM/Ca/Al, which is able to reversibly convert luminous energy to electric energy or electric energy to luminous energy in a single device. By developing a new soft-covered annealing method, we obtained optimized grain morphology with large grain size, high uniformity, and decreased grain boundaries, which is difficult to achieve with conventional fabrication methods. The LEPeSCs exhibits high performance in both PeSCs and PeLEDs modes, with power conversion efficiency of 14.02% in SC mode and bright red-light emission of 1710 cd/cm² at 4 V in LED mode.