Improved efficiency of polymer solar cells via utilizing Alcohol-Soluble Small Molecules N-(2-Carboxyethyl)iminodi acetic acid as cathode interfacial layer

The cathode modification is vital for improving device performance of polymer solar cells (PSCs). Here, N-(2-Carboxyethyl)iminodiacetic acid (C7H11NO6) layers with different concentrations were deposited on the photoactive layer PTB7-Th:PC71BM film, and used as the cathode interface modification material for the conventional device structure of PSCs. By varying the concentration of C7H11NO6, the effect on the performance of PSCs was investigated. It was found that the efficiency of the photovoltaic device was reached as high as 8.86% at a C7H11NO6 concentration of 1 mg mL−1, which was about 56% higher than the performance of the reference device. Among them, the C7H11NO6 film acts as an effective cathode interface layers, forming an interfacial dipole on the surface of the PTB7-Th:PC71BM film to increase the built-in potential and promote photogenerated electron extraction and transport.