Blade-coating of a highly crystallized lead-free silver-bismuth halide double perovskite thin film with improved stability for high-performance photodetection

Abstract

A lead-free double perovskite (Cs₂AgBiBr₆) has recently attracted intense interest for optoelectronic applications owing to its non-toxicity, high stability, and high detection sensitivity. The current goal for the commercial application of perovskite optoelectronic devices is to achieve their large-scale production, while maintaining high performance similar to those produced on a small-scale. Photoluminescence (PL) mapping and time-resolved photoluminescence (TRPL) mapping measurements have shown that grain boundaries are the dominant non-radiative recombination sites. By reducing the grain boundaries, thin films of Cs₂AgBiBr₆ with larger grain sizes can effectively suppress non-radiative recombination, which shows promise for good performance in photodetector applications. In this study, high-quality, large-area (∼10 cm²) Cs₂AgBiBr₆ double perovskite crystal thin films were synthesized via a one-step blade-coating method under ambient conditions. As a result, photoconductors, based on high-quality Cs₂AgBiBr₆ films, exhibited a specific responsivity, R, of 14.47 A W⁻¹ and a high detectivity (D*) of 5.25 × 10¹³ Jones. In addition, the unpackaged devices retained 92% of their initial photoresponsivity after exposure to ambient conditions (humidity ≈ 65%, temperature ≈ 25 °C) for four weeks. The results show that the low-cost blade-coating technique under ambient conditions is an effective approach for the fabrication of large-area Cs₂AgBiBr₆ double perovskite thin films, thus paving the way toward the development of environmentally friendly and high-performance optoelectronic applications.