The investigation of the cathode buffer layer based on perylene diimide for the inverted organic solar cells

Small molecules based on PDI with amino N-oxide (PDIN-O), dimethyldipropylenetriamino, (PDIN-N) and ethyl tosylate (PDIN-OTs) as the cathode buffer layer (CBL) in inverted type OSCs are prepared in this study. The application of PDIN-O as CBL inverted-type devices becomes challenging due to PDIN-O being unstable under heat treatment and tending to degrade. To enhance the thermal stability in the inverted type of devices we introduce the side group dimethyldipropylenetriamino and tosylate. The PCE of the device based on PDIN-O, and PDIN-OTs were 12.5, 13.3, and 14.2%, respectively. This paper provides the ability to modulate CBL in non-fullerene organic solar cells by introducing a side group to tune the work function at the cathode interface. The PDIN-OTs is a promising material for the CBL in the inverted type of device and become the vanguard for the next exploration by changing the counterion or side group side.