Core–Shell CdS–Cu₂S Nanorod Array Solar Cells

As an earth-abundant p-type semiconductor, copper sulfide (Cu₂S) is an attractive material for application in photovoltaic devices. However, it suffers from a minority carrier diffusion length that is less than the length required for complete light absorption. Core–shell nanowires and nanorods have the potential to alleviate this difficulty because they decouple the length scales of light absorption and charge collection. To achieve this geometry using Cu₂S, cation exchange was applied to an array of CdS nanorods to produce well-defined CdS–Cu₂S core–shell nanorods. Previous work has demonstrated single-nanowire photovoltaic devices from this material system, but in this work, the cation exchange chemistry has been applied to nanorod arrays to produce ensemble-level devices with microscale sizes. The core–shell nanorod array devices show power conversion efficiencies of up to 3.8%. In addition, these devices are stable when measured in air after nearly one month of storage in a desiccator. These results are a first step in the development of large-area nanostructured Cu₂S-based photovoltaics that can be processed from solution

Growth and Anion Exchange Conversion of CH₃NH₃PbX₃ Nanorod Arrays for Light-Emitting Diodes

The nanowire and nanorod morphology offers great advantages for application in a range of optoelectronic devices, but these high-quality nanorod arrays are typically based on high temperature growth techniques. Here, we demonstrate the successful room temperature growth of a hybrid perovskite (CH₃NH₃PbBr₃) nanorod array, and we also introduce a new low temperature anion exchange technique to convert the CH₃NH₃PbBr₃ nanorod array into a CH₃NH₃PbI₃ nanorod array while preserving morphology. We demonstrate the application of both these hybrid perovskite nanorod arrays for LEDs. This work highlights the potential utility of postsynthetic interconversion of hybrid perovskites for nanostructured optoelectronic devices such as LEDs, which enables new strategies for the application of hybrid perovskites