Polymer strategies for high-efficiency and stable perovskite solar cells

Polymer strategy has been widely adopted for efficient, stable, and hysteresis-reduced perovskite solar cells (PSCs). Herein, a comprehensive review of polymer strategy is provided, by categorizing the polymers as additives in the perovskite active layer and charge transport layer, as an interfacial layer, and as an encapsulation layer. In addition, the various polymers adopted in polymer strategy and the diverse ways to introduce them into PSCs are summarized. Moreover, the functions of polymers in each layer, such as morphology modulation, energy level alignment adjustment, non-radiative recombination suppression, stability and flexibility enhancement, are emphasized, and the related underlying mechanisms are discussed. Furthermore, future research directions to optimize polymer strategy for further improving the efficiency and stability of PSCs is proposed.