Integration of Type II Nanorod Heterostructures into Photovoltaics

Abstract

High-quality epitaxial interfaces and delicate control over shape anisotropy make nanorod heterostructures (NRHs) with staggered band offsets efficient in separating and directing photogenerated carriers. Combined with versatile and scalable wet chemical means of synthesis, these salient features of NRHs are useful for improving both the performance and the cost-effectiveness of photovoltaics (PVs). However, inefficient carrier transport and extraction have imposed severe limitations, outweighing the benefits of enhanced charge separation. Hence integration of type II NRHs into PVs has thus far been unfruitful. Here, we demonstrate PVs that utilize NRHs as an extremely thin absorber between electron and hole transporting layers. In the limit approaching monolayer thickness, PVs incorporating NRHs have up to three times the short circuit current and conversion efficiency over devices made from their single-component counterparts. Comparisons between linear and curved NRHs are also made, revealing the importance of internal geometry and heterointerfacial area for enhanced contribution of charge-separated state absorption to photocurrent and in contacting charge transport layers.