Performance and Stability Improvement of P3HT:PCBM-Based Solar Cells by Thermally Evaporated Chromium Oxide (CrO_x) Interfacial Layer

We report on thermally evaporated chromium oxide (CrO x ) as cathode interfacial layer to improve the efficiency and stability in air for the bulk heterojunction solar cells of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C 61 butyric acid methyl ester (PCBM). Devices with CrO x interfacial layers show higher power conversion efficiency (PCE) and stability than those without interfacial layer. Devices with CrO x show improved stability more than 100 times that of devices without interfacial layer or with LiF interfacial layer. We tentatively attributed the CrO x interfacial layer as an electronic tunneling layer for electron collection and a protective layer of Al assumably by minimizing the organic−Al interfacial areas caused by the evaporation of Al and blocking diffusion of oxygen and water.