A novel perylene diimide-based zwitterion as the cathode interlayer for high-performance perovskite solar cells

Perovskite solar cells (PSCs) have attracted widespread and intense interest because of their excellent device performance. However, the existence of poor interface contacts and energy losses in the device are key challenges for the development of PSCs in the future. In this work, we developed a novel perylene diimide-based zwitterion (QAPDI) as a cathode interlayer to improve the device performance of inverted PSCs. QAPDI exhibits excellent solubility, appropriate energy levels, and high electron mobility, suggesting that it is a suitable interlayer engineering material in inverted PSCs. The use of QAPDI as a cathode interlayer between the PCBM layer and metal electrode could improve the interface contact and reduce the energy level barrier, thus facilitating efficient electron injection and transport. Moreover, the application of QAPDI could obstruct the permeation of moisture into the perovskite film to reform the device stability. As a consequence, the optimal QAPDI-based device efficiency reached 20.55% together with enhanced device stability compared with that of the control device (18.6%). This work provides an excellent alternative cathode interlayer material for high-performance inverted PSCs.