Role of Self-Trapped Excitons in the Broadband Emission of Lead-Free Perovskite-Inspired Cu 2 AgBiI 6

• Published in: The journal of physical chemistry letters Vol. 14; no. 18; pp. 4192 - 4199
• Main Authors: Grandhi, G Krishnamurthy, Dhama, Rakesh, Viswanath, Noolu Srinivasa Manikanta, Lisitsyna, Ekaterina S, Al-Anesi, Basheer, Dana, Jayanta, Sugathan, Vipinraj, Caglayan, Humeyra, Vivo, Paola
• Format: Journal Article
• Language: English
• Published: United States 11.05.2023
• ISSN: 1948-7185; 1948-7185
• DOI: 10.1021/acs.jpclett.3c00439

The perovskite-inspired Cu AgBiI (CABI) absorber shows promise for low-toxicity indoor photovoltaics. However, the carrier self-trapping in this material limits its photovoltaic performance. Herein, we examine the self-trapping mechanism in CABI by analyzing the excited-state dynamics of its absorption band at 425 nm, which is responsible for the self-trapped exciton emission, using a combination of photoluminescence and ultrafast transient absorption spectroscopies. Photoexcitation in CABI rapidly generates charge carriers in the silver iodide lattice sites, which localize into the self-trapped states and luminesce. Furthermore, a Cu-Ag-I-rich phase that exhibits similar spectral responses as CABI is synthesized, and a comprehensive structural and photophysical study of this phase provides insights into the nature of the excited states of CABI. Overall, this work explains the origin of self-trapping in CABI. This understanding will play a crucial role in optimizing its optoelectronic properties. It also encourages compositional engineering as the key to suppressing self-trapping in CABI.