Bandgap Modulation of Lead-Free Cs₂AgBiBr₆ Double Perovskite via Hydrogen Treatment

The lead-free Cs₂AgBiBr₆ double perovskite has recently emerged as a promising alternative to hybrid lead halide perovskites due to its enhanced stability and nontoxicity. However, the conversion efficiency of Cs₂AgBiBr₆ solar cells remains low, mainly attributed to its wide bandgap, low carrier mobility, and short carrier lifetime. To address these limitations, the effects of hydrogen plasma treatment on Cs₂AgBiBr₆ were systematically investigated by varying treatment times and source powers. SEM, XRD, XPS, and UV-vis analyses were conducted to examine changes in surface morphology, crystallization, composition, and optical properties of the Cs₂AgBiBr₆ films with and without hydrogen plasma treatment. The interface between hydrogen-doped Cs₂AgBiBr₆ and the hole transport layer was then modified with an N719 dye layer. The incorporation of this dye layer into hydrogen-treated Cs₂AgBiBr₆ solar cells had a positive effect on light absorption, charge carrier recombination, carrier extraction, and energy level alignment. Additionally, atomic layer deposited ZnO layer was introduced above or below the hydrogen-doped Cs₂AgBiBr₆ layer to investigate the influence on the interface between the double perovskite and electron transport layer. Electrochemical impedance spectroscopy (EIS) was employed to assess the electrical properties and charge recombination behavior of hydrogen-treated Cs₂AgBiBr₆ solar cells with varying adjacent layers. More details of the stability and performance of hydrogen-doped Cs₂AgBiBr₆ solar cells related to the dye layer and ZnO ALD will be discussed in the presentation.