Unveiling The Efficient Charge Transfer Cascade in Band-Tailored Two-Dimensional WS₂/ Ni Doped CsPbI₃ Heterosystem

Band structure modulation in heterostructure has emerged as a highly effective strategy for fabricating advanced optoelectronic devices. In this work, we have designed a CsPbI₃-WS₂ (CPI-WS₂) heterosystem and employed transient absorption (TA) spectroscopy to gather a comprehensive understanding of charge carrier dynamics. TA study demonstrated the charge delocalization at the interface of CPI and WS₂. Due to the quasi-type II integration of CPI and WS₂, the charge separation in this heterosystem is not very effective, which would restrict their utilization in photovoltaic applications. To further improvise the charge separation, Ni atoms were introduced as dopants into CPI nanocrystals. Ultraviolet electron spectroscopy (UPS) suggested that the homovalent doping elevated the band positions of CPI and resulted in a type II band configuration with WS₂. TA analysis revealed the spontaneous carrier’s separation in band-modulated heterosystem due to the isolation of electrons and holes in discrete semiconductors. These spectroscopy findings were correlated with the optoelectronic performance of heterostructure-based devices. Enhanced charge separation within a doped heterosystem leads to superior optoelectronic performance compared to undoped heterosystems. Our findings showed that the band level of engineering encourages the segregation of charge carriers at the hetero-interface, which would be extremely impactful for designing heterostructure-based optoelectronic systems.