Interface energetics and engineering of organic heterostructures in organic photovoltaic cells

The reliable information about interface energetics of organic materials, especially the energy level alignment at organic het- erostructures is of pronounced importance for unraveling the photon harvesting and charge separation process in organic pho- tovoltaic （OPV） cells. This article provides an overview of interface energetics at typical planar and mixed donor-acceptor het- erostructures, perovskite/organic hybrid interfaces, and their contact interfaces with charge collection layers. The substrate ef- fect on energy level offsets at organic heterostructures and the processes that control and limit the OPV operation are presented Recent efforts on interface engineering with electrical doping are also discussed.