Tuning of defect mediated charge transport in pristine AgBiS2 nanocrystals probed via temperature dependent photoluminescence (TDPL) emission spectroscopy

Abstract

Recently ecofriendly silver bismuth sulfide (AgBiS₂) nanocrystals are widely employed in various photoelectrochemical applications. However, the charge dynamics dictated by charge trapping centers via defect states in AgBiS₂ nanocrystals and the role of annealing temperature beyond 600K in tunning charge trapping centers has not been reported to the best of our knowledge and thereby lack a systemic experimental study. Herein, the tuning of defect states in highly stable pristine (AgBiS₂) nanocrystals is obtained by high temperature annealing spanning from 600K to 900K.The nanocrystals exhibited cubic crystal structure at all annealing temperatures. The sample annealed at 800K showed the highest charge separation which decreased at 900K. We applied temperature dependent photoluminescence (TDPL) spectroscopy measurements within (80K–210K) to investigate the role of intrinsic defect induced trap states thereby influencing charge separation, transfer of electrons to conduction band and possible charge loss centers within the band gap of the samples via non-radiative recombination. Temperature dependent anomalous Berthelot behavior was observed in the TDPL emission spectra of the samples. The sample annealed at 800K showed highest Berthelot energy, least escape energy values for emission peaks It was observed that the bismuth Bi4f_5/2 and Bi4f_7/2 states acted as donor states while Ag centers facilitated carrier hopping, by attaining favorable alignment. The sample annealed at 800K exhibited highest charge transfer efficiency (61 %). These findings contribute to elucidating tuning of temperature-controlled defect induced charge dynamics in pristine AgBiS₂ nanocrystals crucial to harvest their potential for various next generation photoelectrochemical applications.