Exploring Inorganic Hole Collection Materials from Mixed-Metal Dawson-Type Polyoxometalates for Efficient Organic Photovoltaic Devices

Interfacial layer materials play an important role in performance enhancement of organic solar cells (OSCs). Herein, the utilization of mixed-metal Dawson-type polyoxometalates, namely P2Mo3W15O62 (POM-1) and P2Mo9W9O62 (POM-2), as anode interlayer (AIL) materials, for efficiently collecting holes to boost the photovoltaic efficiency of OSCs, is explored. The increase in molybdenum substitution in the mixed-metal POMs can lower the conduction band level and increase the reduction potential. Meanwhile, the high work function of POMs helps to remove the energy barrier in the hole collection, which solves the serious problem of Voc loss in OSCs. As a result, OSCs modified by POM-2 can exhibit superior photovoltaic performance with power conversion efficiency of 14.8%. The results of Mott-Schottky analysis, current density-light intensity dependence, and excitons dissociation probability indicate the efficient hole collection and the depressed charge recombination in the POM-2-based OSC device. By means of fabricating OSCs, the effect of the two POM- based AILs on various photoactive layers is also investigated, and POM-2 exhibits excellent hole collection capability. Moreover, the advantages of low-cost and solution-processable conduct make POM-2 a promising candidate as the AIL material for future mass production of OSCs.