Research Building Room 201

Abstract

Metal halide perovskite is a class of ABX₃-type crystalline materials − in most cases − with the A being both the organic (e.g., formamidinium, methylammonium) and inorganic (e.g., Cs⁺) monovalent cations, B being divalent cations, e.g., Pb²⁺, Sn²⁺, or their mixture, and X being the halide anions, e.g., I⁻, Br⁻, Cl⁻. Thanks to their superior bandgap tunability and high absorption coefficient, metal halide perovskites demonstrate great potential for fabricating both single- and multi-junction photovoltaics capable of achieving high power conversion efficiencies at a low cost^[1,2].

In this lecture, we will first introduce the fundamentals of hybrid perovskite materials and their thin film processing protocols towards the fabrication of solar cell devices. Then, we will exemplify the research with our recent investigations on a specific narrow bandgap (~1.25 eV) perovskite material, i.e., mixed tin−lead perovskites, and their single-junction solar cells, covering the control of the Sn(II) oxidation^[3], interface carrier extraction^[4], and in-situ surface reaction^[5], as well as the understanding of the solution chemistry and resultant thin-film crystallization^[6], from experimental and theoretical aspects. Building on optimizations of a full range of wide bandgap neat lead perovskites (from ~1.5 to ~2.0 eV), in the end, we will showcase the integration of these perovskite sub-cells into “all-perovskite” double-, triple-, and first-ever quadruple-junction solar cells. In addition, we will discuss the lifetime limits of these complex multi-junction photovoltaics and propose promising strategies for enhancing the light and temperature stability of the involved sub-cells. Furthermore, we will also share insights and recent progress obtained in “perovskite-on-silicon” multi-junction cells.

References

1. G. E. Eperon, et al., Nat. Rev. Chem. 2017, 1, 0095.
2. S. Hu et al., Chem. Rev. 2024, 124, 4079–4123.
3. S. Hu et al., Chem. Sci. 2021, 12, 13513–13519.
4. S. Hu et al., Energy Environ. Sci. 2022, 15, 2096–2107.
5. S. Hu et al., Adv. Mater. 2023, 35, 2208320.
6. S. Hu et al., Nature, 2025, 639, 93–101.

Masahiro Ehara (Research Center for Computational Science)