Perovskite solar cell towards lower toxicity: a theoretical study of physical lead reduction strategy

The huge performance enhancements of the organometal halide perovskite solar cells (OHPSCs) have appealed enormous attention within recent ten years. Although the rapid growth of the device power conversion efficiency (PCE) has attained over 25%, the contamination of health-hazardous components still holds back its sustainable applications. To reduce the lead usage, many groups have tried chemical lead reduction solutions: substituting the lead by other group 14 metal elements to realize the low-lead OHPSCs. Unfortunately, neither the PCE nor the stability, low-lead OHPSCs all lag far behind the state-of-the-art conventional lead-based OHPSCs. In this work, we present a physical lead reduction (PLR) concept by reducing the perovskite film thickness to restrict the perovskite hazard risk with minor scarification in device performances. Through the simulation of transfer matrix model, we theoretically demonstrated that by introducing the optical space layer, the device PCE could maintain 96% of the original maximum value while attenuating the perovskite film thickness to one-third. This means that the usage of lead can be reduced by ∼70% with PLR concept, which could have broad appeal as a new lead reduction strategy towards high performance OHPSCs.