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The article studies the band bending, which happen at the interface between a disordered organic semiconductor and a metal electrode using ultraviolet photoemission spectroscopy measurement. Results suggest that band-bending effects due to disorder are expected to reduce the open-circuit voltage in organic photovoltaic devices.

We investigate charge transport in a high-electron mobility polymer, poly(N,N-bis 2-octyldodecyl-naphthalene-1,4,5,8-bis dicarboximide-2,6-diyl-alt-5,5-2,2-bithiophene) [P(NDI2OD-T2), Polyera ActivInk™ N2200]. Time-of-flight measurements reveal electron mobilities approaching those measured in field-effect transistors, the highest ever recorded in a conjugated polymer using this technique. The modest temperature dependence and weak dispersion of the transients indicate low energetic disorder in this material. Steady-state electron-only current measurements reveal a barrier to injection of about 300 meV. We propose that this barrier is located within the P(NDI2OD-T2) film and arises from molecular orientation effects. [ABSTRACT FROM AUTHOR]