• Aslam, Mohammed
• Alam, Aftab
• Bhawna, Bhawna

Abstract

<jats:p> During the past few years, halide double perovskites have been extensively explored for designing eco-friendly and stable perovskite-family absorber materials. In this work, thin films of Cs<jats:sub>2</jats:sub>AgBiBr<jats:sub>6</jats:sub> double perovskites were successfully fabricated with the aim of obtaining a lead-free system. Optical studies confirmed the large band gap of 2.33 eV of Cs<jats:sub>2</jats:sub>AgBiBr<jats:sub>6</jats:sub> films. Post-synthetic vapor treatment of Cs<jats:sub>2</jats:sub>AgBiBr<jats:sub>6</jats:sub> thin films, with tin (IV) iodide (SnI<jats:sub>4</jats:sub>; SI), was performed to engineer their optical response. Structural and optical studies confirmed the phase purity of the various SI-treated films. X-ray diffraction studies further showed a systematic shift toward lower 2θ values, which signified the expansion of lattice parameters on SI substitution in the Cs<jats:sub>2</jats:sub>AgBiBr<jats:sub>6</jats:sub> structure. The as-prepared pristine and SI-treated films showed good coverage with a reasonably large grain size. Furthermore, the optical studies revealed a 0.47 eV reduction in the band gap of SI-treated films, as opposed to a small band-gap change of approximately 0.22 eV when the pristine Cs<jats:sub>2</jats:sub>AgBiBr<jats:sub>6</jats:sub> film was treated with cesium iodide (CsI). This showed the role of the combined effects of charge-balancing defects and compositional substitution in band-gap lowering in Cs<jats:sub>2</jats:sub>AgBiBr<jats:sub>6</jats:sub>. The controlled doping in lead-free double perovskites for improved optical properties might help in strengthening their use for future optoelectronic applications. </jats:p>

Topics

• perovskite
• grain
• grain size
• phase
• x-ray diffraction
• thin film
• defect
• tin