Unfused Electronic Acceptor-Based Polymers as Interfacial Materials for Efficient Inverted Perovskite Solar Cells.

The interfacial issue resulting from surface trap states has become the crucial factor that limits the development of inverted perovskite solar cells (PSCs). Here, three unfused electronic acceptor-based polymers (PC-1-PC-3) with tailored alkyl groups were designed as interfacial materials to modify the interface contact between the perovskite active layer and electron transporting layer (ETL). Among them, PC-2 was found to extract interfacial charge faster and passivate trap states more efficiently. This leads to a remarkable increase in the short-circuit current density (22.49 mA cm-2) and fill factor (0.821), as well as a maximum power conversion efficiency of 20.50% with a negligible hysteresis, which is superior to the PC-1/PC-3 based devices and reference device with only the ETL. This study provides an insight for future molecular design of efficient interfacial materials for inverted PSCs.