Evaporated,\nSemitransparent Rudorffite AgBiI<sub>4</sub> Films for Pb-Free Indoor\nPhotovoltaics

The\ntoxicity of Pb continues to pose a significant risk to the\ncommercialization of perovskite solar cells, particularly in indoor\napplications. Rudorffite Ag<sub><i>x</i></sub>Bi<sub><i>y</i></sub>I<sub><i>x</i>+3<i>y</i></sub> (ABI) with wide bandgap emerges as a promising Pb-free absorber\nfor indoor photovoltaics. Vapor processing allows for precise thickness\ncontrol, easy multilayer film formation, and the potential for large-scale\nproduction. This study introduces the photovoltaic performance of\ndevices employing vapor-processed ABI thin films under indoor light\nillumination for the first time. The hexagonal rudorffite AgBiI<sub>4</sub> thin films, possessing a bandgap of 1.89 eV, were produced\nvia sequential evaporation of BiI<sub>3</sub> and AgI, effectively\ncapturing the spectrum of the white light-emitting diode. Moreover,\nthe transmittance of these ∼65 nm thick AgBiI<sub>4</sub> thin\nfilms demonstrates their potential in semitransparent devices. Devices\nwith these evaporated, semitransparent AgBiI<sub>4</sub> absorbers\nachieved a power conversion efficiency of 2.12% (7.02 μW/cm<sup>2</sup>) under 1000 lx. The stability of these devices was tested\nin an ambient atmosphere without encapsulation. Accelerated degradation\nwas observed under 1000 lx compared to 1 sun, indicating increased\nsensitivity to aging under low light intensities.