Evaluating Lead-Based vs. Lead-Free Perovskites for Environmentally Sustainable Indoor Photovoltaics

Abstract Indoor photovoltaics (IPVs) based on halide perovskites (HPs) and derivatives (HPDs) hold great promise for powering the vast infrastructure of Internet-of-Things (IoT) smart devices. While lead-containing IPVs deliver cutting-edge performance, environmental concerns have spurred research into lead-free alternatives. However, the environmental sustainability of these IPV technologies remains underexplored, with the lead-based versus lead-free debate confined to elemental considerations, neglecting life-cycle impacts and IPV requirements. This study presents the first comparative life-cycle assessment (LCA) addressing the lead-based vs. lead-free HP/HPD IPV dilemma, examining the environmental sustainability of absorbers, precursors, functional layers, and fabrication steps. A modelling framework is introduced to evaluate the net environmental gains (NEGs) of IPVs compared to the conventional battery-centric approach for powering smart devices. Our findings challenge conventional assumptions that lead-free HP/HPD IPVs are inherently more eco-friendly than their lead-based counterparts. Moreover, we demonstrate that Pb- and Sn-based IPVs can achieve NEGs after just 3–4 weeks and 4–7 weeks, respectively, significantly outperforming mainstream IPVs. In contrast, the NEGs of Sb- and Bi-based IPVs align with mainstream IPVs, limiting their potential unless efficiencies increase to ~40%. Key strategies to enhance the eco-friendliness of HP/HPD IPVs and policy considerations on Pb-based IPVs for IoT sustainability are outlined.