The balance between efficiency, stability and environmental impacts in perovskite solar cells: a review

Photovoltaic technology is progressing very fast, both in a new installed capacity, now reaching a total of more than 400 GW worldwide, and in a big research effort to develop more efficient and sustainable technologies. Organic and hybrid solar cells have been pointed out as a technological breakthrough due to their potential for low economical cost and low environmental impact; but despite impressive laboratory progress, the market is still beyond reach for these technologies, especially for perovskite-based technology. In this review, the historical evolution and relationship of efficiency and stability is addressed, including Life Cycle Assessment studies which provide a quantitative evaluation of environmental impacts in several categories, such as human health or freshwater ecotoxicity, with special focus on lead toxicity. The main conclusion is that there is no unsurmountable barrier for the massive deployment of photovoltaic systems with perovskite solar modules, if the stability is extended to lifetimes similar to technologies already in the market. The results of this review provide some recommendations mainly focused on the best options for improved stability (avoiding mainly moisture and oxygen degradation) by using metal oxides, ternary or quaternary cations, or the novel 2D/3D approach, and the encapsulation effort which should also take into account the recyclability of the materials and the low environmental impact processes for up-scaled industrial production. Research guidelines should take into account the end-of-life of the devices and cleaner routes for production avoiding toxic solvents.