Sichuan University EES: 26.01%! Crystal Phase and Band Edge Modulation of MA- and Br-Free CsFA-Based Perovskites

2025/8/29 11:25:22 admin 阅读 163【次】

A research paper titled "Crystal phase and band edge modulation of MA- and Br-free CsFA-based perovskite for efficient inverted solar cells and minimodules" was published in the journal Energy & Environmental Science by Wu Yihui and Peng Qiang, with Yang Jiewei as the first author and Wu Yihui and Peng Qiang as co-corresponding authors.

Key Highlights: This paper proposes a crystal growth and band edge modulation strategy for MA- and Br-free CsFA-based perovskite (Cs0.05FA0.95PbI3). The Lewis base of methyl (methylsulfinyl) methyl sulfide (MMS) was rationally selected as the crystal growth medium to minimize non-radiative voltage losses. The team achieved a reverse scan efficiency of 26.01% for a 0.09 cm2 inverted perovskite solar cell and a quasi-steady-state output efficiency of 25.30%. The champion device achieved a minimum non-radiative voltage loss of 67 mV. The results were also scaled up to a micromodule with an active area of 12.96 cm2, achieving a reverse scan efficiency of 22.67%. Compared to MA- and Br-containing perovskite materials, methylammonium (MA)- and Br-free CsFA-based perovskites have attracted increasing attention due to their enhanced thermal stability and broader spectral response. However, the inhomogeneous distribution of Cs and FA cations hinders the regulation of trap-related non-radiative voltage losses. However, trap-related non-radiative voltage losses (V_loss^(non-rad)) are a key factor limiting the performance of inverse perovskite solar cells (PSCs). To date, no successful attempts have been made to fabricate high-quality, phase-pure MA- and Br-free CsFA-based perovskite films with extended band edges without modifying the perovskite composition.

In light of this, the team of Wu Yihui and Peng Qiang from Sichuan University manipulated the crystal growth and spectral response of MA/Br-free CsFA-based perovskites by rationally introducing methyl(methylsulfinyl)methyl sulfide (MMS) into the precursor to minimize the non-radiative voltage losses. MMS effectively inhibits halide oxidation and reduces the formation of δ-phase perovskite during the phase transition, resulting in high-quality perovskite films with fewer defects and reduced non-radiative recombination. Notably, the perovskite band edge achieves a 5nm redshift, providing an additional integrated current density of 0.24 mA/cm². Consequently, a 0.09 cm² inverse perovskite solar cell achieves a reverse scan efficiency of 26.01% and a quasi-steady-state output efficiency of 25.30%, the highest values to date for inverse perovskite solar cells based on MA/Br-free CsFA dual-cation perovskites. The champion device achieves a minimum non-radiative voltage loss of 67 mV. This strategy was also extended to a micromodule with an active area of 12.96 cm², achieving a reverse scan efficiency of 22.67%. Furthermore, the unencapsulated target device exhibited excellent long-term thermal aging and operational stability: after 1000 hours of continuous thermal aging on an 85°C hot plate and 1650 hours of maximum power point tracking (MPPT) under 1-sun illumination (white LED array) at 30±5°C, its original efficiency remained above 75% and 82%, respectively, outperforming the control device.

This study provides a simple and effective Lewis base for producing high-efficiency light absorbers with high quality and extended spectral response. By optimizing interfacial contacts, film quality, and subcell connections, the performance of small-scale PSCs and perovskite solar modules is expected to be further improved. It also highlights the importance of minimizing non-radiative voltage losses for high-performance inverse perovskite solar cells.

Source：DOI: 10.1039/D4EE05860G.
https://doi.org/10.1039/D4EE05860G

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Sichuan University EES: 26.01%! Crystal Phase and Band Edge Modulation of MA- and Br-Free CsFA-Based Perovskites

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