Heterojunction engineering has played an indispensable role in the exploitation of innovative artificial materials with exceptional properties and has consequently triggered a new revolution in achieving high-performance optoelectronic devices. Herein, an intriguing halide perovskite (PVK) and metal dichalcogenide (MD) heterojunction, i.e., a lead-free Cs2SnI6 perovskite nanocrystal/SnS2 nanosheet hybrid, was fabricated in situ for the first time. Comprehensive investigations with experimental characterizations and theoretical calculations demonstrate that cosharing of the Sn atom enables intimate contact in the Cs2SnI6/SnS2 hybrid together with a type II band alignment structure. Additionally, ultrafast carrier separation between SnS2 and Cs2SnI6 has been observed in the Cs2SnI6/SnS2 hybrid by transient absorption measurements, which efficiently prolongs the lifetime of the photogenerated electrons in SnS2 (from 1290 to 3080 ps). The resultant spatial charge separation in the Cs2SnI6/SnS2 hybrid evidenced by Kelvin probe force microscopy (KPFM) significantly boosts the photocatalytic activity toward CO2 reduction and the photoelectrochemical performance, with 5.4-fold and 10.6-fold enhancements compared with unadorned SnS2. This work provides a facile and effective method for the in situ preparation of PVK-MD heterojunctions, which may significantly stimulate the synthesis of various perovskite-based hybrid materials and their further optoelectronic applications.
Saqib Nawaz Khan,Huili Liang,Yan Wang,Xiaolong Du,Zengxia Mei
With the advancement of perovskite research, there is a growing urgency to address the imperative need for practical applications while simultaneously tackling the enduring challenges of material reliability and lead (Pb) toxicity. The crystallization, morphology and optical properties of the resultant film and device performance during solution processing are heavily influenced by the solution-based intermediate, a state determined using the coordination between solute and solvent. Solvent–solute coordination is closely correlated with solvent characteristics including ionization capabilities, dielectric constant, hydrolysis, and reactivity with solutes. Deionized water (D-water) characterized by its high polarity, ionization capability, and dielectric constant, when used as a co-solvent with dimethylformamide (DMF) and dimethyl sulfoxide (DMSO), facilitates stronger coordination with CsI/SnI4 species in Cs2SnI6 precursor solution. This enhanced coordination leads to improved solvation, precursor reactivity, and solution homogeneity. Incorporating an appropriate amount of D-water as a co-solvent into Cs2SnI6 precursor solution allows for tuning solvent coordination and control over the resulting thin film crystallization and morphology. The co-solvent diluted optimized Cs2SnI6 thin film leads to the fabrication of energy-efficient broadband 4 × 3 photodetector arrays ranging from UV to NIR giving a responsivity of 5.5 A W−1 at a substantially lower bias voltage of −0.1 V with stable operation stability in ambient air. These findings underscore the potential advantages of solution-processed Cs2SnI6 perovskites in various optoelectronic applications.
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