Improving performance of carrier extraction by using ZnO nanorod array in PBDTTT-C-T: PC71BM polymer photovoltaics with inverted structure

Applying ZnO nanorod array in organic solar cells is a good method to improve the device power conversion efficiency. The method has broad applicability potential in various kinds of material systems. In this work, we control ZnO nanorod morphlogy to increase the total contact area and provide straight channels for carrier extraction in PBDTTT-C-T:PC₇₁BM inverted solar cells. In optimization, we adjust the ratio of zinc nitrate and HMT in growth-promoting solution to control the ZnO nanorod array morphology for good polymer infiltration. As a result, J_SC is enhanced from 11.6mA/cm² to 16.5mA/cm², and PCE is increased from about 5% to above 7%.