Facile in situ synthesis of double perovskite Cs2AgBiBr6/WS2 heterostructure and interfacial charge transfer mediated high-performance ultraviolet photodetection

Abstract

While lead-based halide perovskites have demonstrated exceptional performance in photovoltaic and other optoelectronic applications globally, the inherent toxicity of lead (Pb) has consistently posed a barrier to widespread commercialization. As such, Pb-free halide perovskites have garnered enormous attention in optoelectronics due to their reduced toxicity, superior absorption in the UV-visible range, and high stability compared to Pb-based halide perovskites. On the other hand, 2D transition metal dichalcogenides (TMDCs) have gained significant attention due to their remarkably sensitive light detection capabilities. Herein, we have introduced a successful way to fabricate Cs₂AgBiBr₆/WS₂ local heterostructures via a low-cost mechanochemical approach to improve the optoelectronic properties, including the photodetection performance, of a planar photodetector device. In the Cs₂AgBiBr₆/WS₂ heterostructure, the noticeable shift in the Raman A_1g and E_2g modes of WS₂ indicates the charge transfer and milling-induced strain, respectively. As compared to the bare Cs₂AgBiBr₆, the heterostructure exhibits an improved current on/off ratio of ∼5.9 × 10³, a high responsivity of 2.01 A W⁻¹, and a high specific detectivity of 3.6 × 10¹³ Jones under 405 nm laser illumination. The higher light-to-dark current ratio and efficient charge transfer are credited to enhanced charge carrier generation and collection of the photocarriers within the Cs₂AgBiBr₆/WS₂ heterostructure. This is supported by enhanced absorbance, photoluminescence (PL) quenching, and shortened photocarrier lifetime (from 3.65 ns to 0.82 ns). XPS and UPS measurements confirmed the effective charge transfer from Cs₂AgBiBr₆ double perovskite (DP) to WS₂ nanosheets. The Cs₂AgBiBr₆/WS₂ heterostructure is believed to form a local p–n junction at the interface, enhancing carrier separation. The resulting heterostructure exhibits a significant photocurrent even at 0 V bias making the device self-powered in nature. The high linear dynamic range (LDR) (75 dB), fast photoresponse speed (80 ms/120 ms), and self-powered behavior signify promising prospects for low-power consumption optoelectronic devices in the future.