Additive strategy to regulate crystallization and charge carrier dynamics of CsBi3I10 towards efficient and stable thin film solar cells

• Pb(SCN) 2 is doped into CBI to tailor film crystallization and morphology. • Carrier recombination at interfaces has been inhibited. • CBI film exhibits high conductivity and remarkable moisture tolerance. • The additives enable a record efficiency of 1.13% for planar CBI solar cells. All-inorganic semiconductor CsBi 3 I 10 (CBI) has recently been recognized as promising alternatives to lead-based light harvesting materials. However, poor film quality and high defects greatly limit its photovoltaic performance in solar cell applications. Here, a simple and effective multifunctional additive of lead thiocyanate (Pb(SCN) 2 ) is doped into CBI for tailoring film morphology and optoelectronic properties. Synergistic effects of Pb 2+ and pseudohalide SCN - enable fine regulation of CBI crystallization as well as defects passivation, resulting in the formation of high-quality thin film with desirable uniformity, negligible pinholes, high electrical conductivity and remarkable moisture tolerance. The additive Pb(SCN) 2 can efficiently alleviate moisture-induced degradation mechanism by inhibiting the phase transition from CBI to Cs 3 Bi 2 I 9 . In addition, the resulting solar cells exhibit significantly enhanced carrier lifetime, reduced charge recombination and increased charge collection yield, leading to a record efficiency of 1.13% for planar CBI-based thin film solar cells. This work suggests additive engineering is efficient to modulate film properties and solar cell performance, which could be generally applicable to fabricate other Bi-based thin film and optoelectronic devices.