Br-rich perovskites for multijunction solar cells

Junke Wang^a^,^b, Shuaifeng Hu^b^,^c, Zehua Chen^d, Xinyi Shen^e, Yen-Hung Lin^e, Henry Snaith^b

^aState Key Laboratory of Luminescent Materials and Devices, School of Materials Science and Engineering, South China University of Technology, Guangzhou 510640, China

^bClarendon Laboratory, Department of Physics, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom

^cDepartment of Chemistry, The University of Hong Kong, Hong Kong, China

^dBeijing Computational Science Research Center, Beijing 100193, China

^eDepartment of Electronic and Computer Engineering, The Hong Kong University of Science and Technology, Hong Kong, China

Proceedings of MATSUS Fall 2026 Conference (MATSUSFall26)

A1 Beyond Efficiency: Perovskite Optoelectronics for Scalable and Stable Devices

Palma, Spain, 2026 October 26th - 30th

Organizers: Guixiang Li and Silver-Hamill Turren-Cruz

Invited Speaker, Junke Wang, presentation 275
Publication date: 22nd July 2026

All-perovskite multijunction solar cells promise to deliver power conversion efficiencies (PCEs) beyond the theoretical limit of single-junction devices at low fabrication costs. However, the sub-par performance of wide-bandgap perovskite subcells remains a key bottleneck limiting the efficiency gains of tandem architectures.

In this presentation, I will discuss how initial morphological and compositional disorder in as-deposited Br-rich, wide-bandgap perovskite films can be the primary cause of V_OC losses and stability issues in high-bandgap perovskite solar cells. I will then present our latest mitigation strategies based on templated growth of Br-rich perovskites, which improve halide homogeneity and suppress energetic losses, achieving open-circuit voltages approaching 90% of the theoretical limit across photovoltaic bandgaps ranging from 1.8 to 2.3 eV.

Building on these advances, we demonstrate efficient monolithic all-perovskite double-junction, triple-junction, and quadruple-junction solar cells with PCEs beyond 27% at a 1 cm² device area.

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