Yb3+ doped Cs2AgIn1-xBixCl6 Double Perovskite Nanocrystals

Abstract

Cs2AgInCl6 is a direct band gap double perovskite (DP) having thermal and moisture stability. However, Cs2AgInCl6 exhibits wide band gap with poor optical absorption and emission in the visible region. Incorporation of Bi in the form of Cs2AgIn1-xBixCl6 alloy introduce a new lower energy absorption channels because of the Bi3+ 6s2 electrons. Also Bi3+ incorporation increases the intensity of broad visible-light emission. In this thesis, we have prepared colloidal Yb3+ doped Cs2AgIn1-xBixCl6 nanocrystals (NCs). The Yb3+ dopants introduce near-infrared (NIR) emission with peak at ~996 nm corresponding to 2F5/2 → 2F7/2 transition of Yb3+ f-electrons. Whereas, the NCs provides solution processability, which is required for fabrication of any thin film device. We have optimized the Yb3+ and Bi3+ concentration to get the high NIR emission at low excitation energy. Alloying with Bi3+ decreases the excitation energy such that commercial UV light emitting diodes (LEDs) can be used for excitation source. Future work in this direction may lead to the development NIR LEDs.