Improvement of interfacial contacts for new small-molecule bulk-heterojunction organic photovoltaics.

The influence of protonation reactions between poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and a thiadiazolo[3,4-c]pyridine small-molecule donor are reported; these result in poor solar-cell performance due to a barrier for charge extraction. The use of a NiO(x) contact eliminates such deleterious chemical interactions and results in substantial improvements in open-circuit voltage, fill factor, and an increased power conversion efficiency from 2.3% to 5.1%.