Abstract: In order to increase the power conversion efficiency of organic solar cells, a novel cathode interfacial layer is proposed. Graphene quantum dots (GQDs) are prepared by electrochemical method, and nitrogen-modified graphene quantum dots (N-GQDs) are obtained by modifying GQDs with branched polyethylenimine (BPEI). N-GQDs have good water solubility and dispersion, it is easy to be deposited films by spin-coating technique. Besides, it has small size, large specific surface area, and good electrical conductivity. It is applied as the cathode interfacial layer in inverted organic solar cells to prepare devices with configuration of ITO/N-GQDs/PCE-10:PC₇₁BM/MoO₃/Al, N-GQDs improve electron mobility and reduce the work function of ITO. The results show that, compared with ITO and ITO/ZnO, ITO/N-GQDs have higher light transmission and electronic conductivity, and the power conversion efficiency of organic solar cells with ITO/N-GQDs is improved to 8.64%.