Improvement in the Photocurrent of Inverted Organic Solar Cells Using MoO _x -Doped TAPC as a P-Type Optical Spacer

In this work, we demonstrate enhancement in the short-circuit current of inverted organic photovoltaic cells (OPVs) using a P-type optical spacer. The P-type optical spacer, which consists of molybdenum oxide (MoO _x -doped 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC), shows improved transmittance at visible light with high electrical conductivity. The electrical field distribution of incident light at the active layer of OPVs can be controlled by tuning the thickness of the optical spacer in the OPVs. Specifically, the incorporation of the 20-nm optical spacer layer in the OPV leads to enhanced spectral response of the device in the wavelength range of 400–600 nm, which is consistent with the combined results of improved optical absorption and better charge transport characteristics. As a result, the OPV with a 20-nm P-type optical spacer shows improvement in the short-circuit current compared with a device with 10 nm of embedded MoO _x .