Control of Nanocrystal Surface Defects for Efficient Charge Extraction in Polymer-Zno Photovoltaic Systems

Factors determining the photovoltaic device performance of blends of regioregular poly(3-hexylthiophene) (rr-P3HT) and ZnO nanostructures are reported. A decrease in the crystallinity of rr-P3HT upon the formation of ZnO (through hydrolysis) is observed through optical absorption spectroscopy. Increasing the humidity level for the ZnO formation leads to a decrease in the photoluminescence of the rr-P3HT:ZnO blend together with improved photovoltaic device performance. This is attributed to more efficient charge extraction due to a decrease in the radiative trap sites on the ZnO surface as a result of decreasing ZnO surface area with increasing humidity level.