Small-molecule organic solar cells with improved stability

A stable small-molecule organic photovoltaic device with structure of ITO⧹donor⧹acceptor⧹buffer⧹cathode is presented. A thin layer (∼60 Å) of tris-8-hydroxy-quinolinato aluminum (Alq3) instead of bathocuproine (BCP) is adopted as the buffer of the device, resulting in 150 times longer lifetime. The power conversion efficiency of the device is 2.11% under 75 mW/cm2 AM1.5G simulated illumination, and no perceptible efficiency degradation is observed for long-term storage of the device in vacuum or nitrogen-filled glove box. More effective blocking of Alq3 than BCP against diffusion of cathode atoms and permeation of oxygen and/or water molecules is considered as the main reason for the improved performance of the new device.