AgInS2–ZnS quantum dots. Excited state interactions with TiO2 and photovoltaic performance

Multinary quantum dots such as AgInS2 and alloyed AgInS2–ZnS are an emerging class of semiconductor materials for applications in photovoltaic and display devices. The nanocrystals of (AgInS2)x–(ZnS)1–x (for x = 0.67) exhibit a broad emission with a maximum at 623 nm and interact strongly with TiO2 nanostructures by injecting electrons from the excited state. The electron transfer rate constant as determined from transient absorption spectroscopy was 1.8 × 1010 s–1. The photovoltaic performance was evaluated over a period of a few weeks to demonstrate the stability of AgInS2–ZnS when utilized as sensitizers in solar cells. We report a power conversion efficiency of 2.25% of our champion cell 1 month after its fabrication. The limitations of AgInS2–ZnS nanocrystals in achieving greater solar cell efficiency are discussed.