Fabrication of High‐Quality CsBi₃I₁₀ Films via a Gas‐Assisted Approach for Efficient Lead‐Free Perovskite Solar Cells

Abstract

Bismuth‐based perovskites are promising candidates for lead‐free and air‐stable photovoltaics. However, the poor surface morphologies and high exciton binding energy of the bismuth‐based perovskites have limited their performances. Herein, the density functional theory calculations unveil that CsBi3I10 possesses favorable optoelectronic properties such as a narrow bandgap, a small effective mass, and relatively high electron mobility. To tackle the poor‐surface morphology problem, the high‐quality CsBi3I10 films are fabricated via gas‐assisted spin‐coating and solvent vapor annealing in ambient conditions. Using the [6,6]‐phenyl‐C61‐butyric acid methyl ester (PCBM) as the electron acceptor, an optimized inverted CsBi3I10/PCBM bulk‐heterojunction structure enables a high power conversion efficiency of 1.18% among the CsBi3I10‐based perovskite solar cells. The approach exemplified in this work could be useful for designing the high‐performance Bi‐based lead‐free perovskite solar cells.

LARP-assisted synthesis of CsBi3I10 perovskite for efficient lead-free solar cells

“… 2 Metal cations such as Sn 2+ , Sb 3+ , and Bi 3+ with ns 2 valence electron configuration are explored as the most suitable candidates to replace Pb in lead halide perovskites. 3 Among these, Sn 2+ can be easily oxidized to Sn 4+ which seriously affects the crystal structure, stability, and device performance. Therefore, it is worth searching for an alternative that can show similar performance to Pb-based perovskite and is stable under ambient conditions.…”

“…The absorption coefficient of CsBi 3 I 10 is found to be 1.4 × 10 5 cm −1 with a large carrier lifetime and enhanced stability under ambient conditions. 3 Moreover, CsBi 3 I 10 exhibits a narrow bandgap of 1.77 eV, which is highly demanded in the field of photovoltaics. 1 It would therefore be a good choice to consider CsBi 3 I 10 as a promising alternative to Pb-based devices.…”

“…The device assembled with the [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as an electron acceptor delivered a high PCE of 1.18%. 3 …”

“… 4 According to the literature, achieving a high-quality thin film of CsBi 3 I 10 is still a challenging task. 3 …”

“…The device assembled with the [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as an electron acceptor delivered a high PCE of 1.18%. 3 In recent years, researchers have focused on improving the device performance by tuning the bandgap, improving the lm quality, morphological tuning, etc. 6 Khadka et al 4 explored different annealing approaches such as conventional annealing (CA), antisolvent (AS), and subsequent ambient solvent vapor annealing (AS + SA) to tailor the CsBi 3 I 10 lm morphology.…”