Designing Stable Perovskite Solar Cells

Researchers at EPFL’s School of Basic Science have developed a method to make perovskite solar cells more durable and efficient.

Perovskite solar cells are considered to replace the current form of silicon based photovoltaics. This technology has attracted much attention because it offers increased light harvesting capacity combined with a low manufacturing cost, making perovskite solar cells (PSCs) prime candidates for replacing current silicon-based devices.

Perovskite solar cells are constructed from nano-sized crystals that can be dispersed into a liquid and spin-coated onto a surface using low-cost, well-established techniques. But a problem with the commercialization of these cells is their operational stability, which puts them at a disadvantage compared to photovoltaic technologies that are already on the market. This is especially a problem with mixed-halide perovskites, which are ideal materials for tandem solar cells and emission-tunable LEDs because they combine high compositional flexibility with optoelectronic performance.

A group of researchers at EPFL’s School of Basic Sciences has now developed a method that improves both power conversion efficiency and stability, in solar cells based on pure iodide as well as mixed-halide perovskites, while also suppressing the halide phase. segregation of the latter.

The method treats PSCs with two alkylammonium halide modulators that work synergistically to improve solar cell performance. Modulators are used as passivators, compounds used to reduce defects in perovskites, which otherwise promote the above-mentioned degradation pathways. The researchers were able to use two modulators to stop the halide segregation and thus significantly reduce the drops in power-conversion efficiency seen in the long-term use of PSCs.

The new method resulted in power-conversion efficiencies of 24.9% for one perovskite composition (α-FAPbI3) and 21.2% for another (FA65MA35Pb(I65Br35)3). About 90% and 80% of the initial efficiencies are retained after 1200 and 250 hours of continuous operation, respectively. The authors write, “By addressing the critical issue of stability, our results represent an important step toward large-scale practical applications of PSCs.”

References: Michael Graetzel, Cooperative Passivation of Perovskite Solar Cells by Alkyldimethylammonium Halide Amphiphiles, Joule (2022). DOI: 10.1016/j.joule.2022.11.013. www.cell.com/joule/fulltext/S2542-4351(22)00571-2