Donor-acceptor interfacial interactions dominate device performance in hybrid P3HT-ZnO nanowire-array solar cells

The adsorption of self-assembled monolayers (SAMs) on metal oxide surfaces is a promising route to control electronic characteristics and surface wettability. Here, arylphosphonic acid derivatives are used to modulate the surface properties of vertically oriented ZnO nanowire arrays. Arylphosphonate-functionalized ZnO nanowires are incorporated into hybrid organic-inorganic solar cells in which infiltrated poly(3-hexylthiophene) (P3HT) serves as the polymer donor. Strong correlations between device short-circuit current density (J _sc) and power conversion efficiencies (PCEs) with ZnO surface functionalization species are observed and a weak correlation in the open-circuit voltage (V _oc) is observed. Inverted solar cells fabricated with these treated interfaces exhibit PCEs as high as 2.1%, primarily due to improvements in J _sc. Analogous devices using untreated ZnO arrays having efficiencies of 1.6%. The enhancement in J _sc is attributed to surface passivation of ZnO by SAMs and enhanced wettability from P3HT, which improve charge transfer and reduce carrier recombination at the organic-inorganic interface in the solar cells. The adsorption of interfacial molecular layers provides a way to improve device performance. Arylphosphonate-modified ZnO nanowire array-poly(3-hexylthiophene) (P3HT) hybrid photovoltaics are fabricated, and inverted solar cells made with these treated interfaces exhibit power conversion efficiencies as high as 2.1%. This is due to improvements in the short-circuit current density, which can be attributed to surface passivation of ZnO and enhanced wettability from P3HT.