Enhanced optoelectronic performance in AgBiS2 nanocrystals obtained via an improved amine-based synthesis route

AgBiS2 nanocrystals are good candidates in optoelectronic applications due to their solution-processability, earth abundance and non-toxic properties. AgBiS2 thin film solar cells have demonstrated promising performance due to their high absorption coefficients and suitable bandgaps for light harvesting. However, their physical properties such as mobility, carrier concentration and photosensitivity, which are very important for photovoltaics, remain unreported. Herein, we develop an improved amine-based synthesis route and systematically investigate these properties by characterizing field effect transistors and photodetectors fabricated from AgBiS2 nanocrystals. We found that the amine-based synthesis improved their measurable semiconducting properties and their solar cell performance. The optimal thickness of a champion solar cell was found to increase to 65 nm, which achieved a power conversion efficiency of 4.3% based on a ZnO/AgBiS2/P3HT/Au device structure, compared with 35 nm of a champion solar cell with a power conversion efficiency of 3.9% reported previously. This modified approach could be applied in the preparation of other high quality nanocrystals that uses silver, where single valence Ag cations are of increasing importance in stable solution processed nanomaterials.