The escalating demand for sustainable energy solutions in recent years has highlighted the potential of indoor photovoltaics (IPVs) as a viable alternative for powering Internet of Things (IoT) devices. While lead halide perovskites have emerged as frontrunners due to their remarkable power conversion efficiencies (PCE) nearing 45% under indoor lighting conditions, their inclusion of toxic lead has prompted a thorough investigation into safer alternatives. This communication focuses on the sustainability of lead-free perovskite-inspired materials (PIMs), particularly those containing pnictogens such as bismuth (Bi) and antimony (Sb), as promising candidates for IPV applications.[1],[2]

The development of eco-friendly IPV technologies is crucial for reducing reliance on batteries which contribute to environmental degradation through resource extraction and waste generation. Traditional IPV technologies based on amorphous hydrogenated silicon (a-Si:H) offer PCE values up to 30%. However, the innovative use of lead-free PIMs has shown PCEs approaching 10% in early research phases, indicating significant potential for future advancements. This study utilizes a life-cycle assessment (LCA) approach to evaluate the environmental impacts of various PIMs, emphasizing their raw material availability, energy consumption, and waste generation.

Our findings reveal that while the PCE of PIMs plays a pivotal role in their overall environmental footprint and components such as the metal electrode and charge transport layers significantly influence their sustainability. Among the evaluated materials, a Bi-Sb alloy emerged as the most promising candidate, demonstrating a reduced environmental burden compared to a-Si:H under industrial-scale processing conditions. Extended simulations indicate that the industrial-scale implementation of Bi-PIMs can lead to a notable decrease in cumulative energy demand and carbon emissions, showcasing their potential as sustainable IPV technologies.

Moreover, this research underscores the critical importance of exploring the toxicity and criticality of raw materials used in the synthesis of these PIMs. While bismuth is recognized for its negligible toxicity and has been utilized in medical applications, antimony presents concerns regarding its occupational exposure risks.

In conclusion, the sustainability of lead-free PIMs for IPV applications is multi-faceted, encompassing not only their energy conversion efficiencies but also their environmental impacts throughout their lifecycle. Our study provides the first robust evidence of the potential for pnictogen-based PIMs to serve as viable, eco-friendly alternatives to lead-based materials, thereby addressing the growing need for sustainable energy solutions in the rapidly expanding IoT landscape. Future research efforts should focus on optimizing the efficiency of these materials while minimizing their environmental footprints, advancing the development of cost-effective and sustainable IPV technologies. The findings presented herein are crucial for guiding the scientific community and policymakers towards the realization of sustainable energy solutions that are not only efficient but also environmentally responsible.