Application of transferred top electrode in perovskite solar cells

Recent years, perovskite solar cells have been developing rapidly because of the high efficiency, ease of preparation and low cost. To the preparation and optimization of multilayer structures for perovskite devices, researchers always pay most attention on the perovskite light absorber and charge-transporting layers. While in the case of the top electrode, evaporated Au electrodes can work well as a standard method at the current laboratory stage. Therefore, the top electrode issue is easily overlooked by researchers. However, the high cost of equipments and raw materials for evaporated precious metal electrodes will not be ignored in the large-area devices manufacturing and large-scale applications of perovskite solar cells. Several non-evaporation processes such as conductive film transferring or conductive paste coating have been developed to solve these problems. Herein, we addresses the current progress of transfer methods top electrodes from the perspective of process techniques. A variety of material systems including metals, polymers and carbon are compared to summarize some general principles. Also, the shortcomings of the transfer method, and bottlenecks of materials and potential solutions for ideal transfer electrodes are discussed.