Band alignment effects at the metal electrode interface of poly(3-hexylthiophene):zinc oxide hybrid photovoltaics

Photoelectron spectroscopy is used to investigate the role of titanium oxide as an interfacial layer between a hybrid regioregular poly(3-hexylthiophene):zinc oxide photoactive layer and the Al back contact. The inspection of chemical bonds through X-ray photoemission spectroscopy core peaks indicates that the inner structure of the rr-P3HT:ZnO photo-active layer is preserved, subsequent to the deposition of the TiOx layer. Furthermore, the band alignment of rr-P3HT:ZnO/TiOx and TiOx/Al interfaces gives rise to the enhancement in device efficiency from 1.08% to 1.22% upon incorporating the TiOx layer, which is associated with the additional open circuit voltage obtained in the interface of P3HT:ZnO/TiOx. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4794402]