Synthesis and Photophysical Properties of Ternary I-III-VI AgInS2 Nanocrystals: Intrinsic versus Surface States

Ternary I-III-VI AgInS2 (AIS) semiconductor nanocrystals (NCs) with strong photoluminescence (PL) were synthesized using a one-pot reaction at low temperature. UV-vis absorption and PL spectra red shifted as the AIS NCs grew. Both steady-state and time-resolved PL spectroscopies were used to investigate the influence of surface and intrinsic trap states on the PL behaviors of the prepared AIS NCs. PL lifetimes at different wavelengths in the full spectrum range were measured using a streak camera for each sample toward a systematic kinetic study. We found PL lifetime components that were short-lived from surface states and long-lived from intrinsic states. Surface trap emissions were wavelength- and size-dependent. Besides these PL studies, we report the first measurements using femtosecond transient absorption spectroscopy to investigate the exciton dynamics of the AIS NCs. Because of the abundant intrinsic trap states, these ternary AIS NCs have long-lived excitons, which may provide potential applications in photocatalysis and photovoltaics.