Indoor application of emerging photovoltaics-progress, challenges and perspectives

The development of solution-processed photovoltaic (PV) devices for indoor applications has recently attracted widespread attention owing to their outstanding potential in harvesting energy efficiently for low-power-consumption electronic devices, such as wireless sensors and internet of things (IoT). In particular, organic PVs (OPVs), perovskite PVs (PPVs) and quantum dot PVs (QDPVs) are among the most promising emerging photovoltaic technologies that have already demonstrated strong commercialisation potential for this new market, owing to their excellent yet highly tuneable optoelectronic properties to meet the demands for specific applications. In this review, we summarise the recent progress in the development of OPVs, PPVs and QDPVs for indoor applications, showing the rapid advances in their device performance in conjunction with highly diverse materials and device designs, including semi-transparent, flexible and large-area devices. The remaining challenges of these emerging indoor PV technologies that need to be urgently addressed toward their commercialisation, including, in particular, their limited stability and high ecotoxicity, will be discussed in detail. Potential strategies to address these challenges will also be proposed.