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

We report on thermally evaporated chromium oxide (CrOx) 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 CrOx interfacial layers show higher power conversion efficiency (PCE) and stability than those without interfacial layer. Devices with CrOx show improved stability more than 100 times that of devices without interfacial layer or with LiF interfacial layer. We tentatively attributed the CrOx 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.