Yb-Doped Cs2AgInCl6 Double Perovskite Microcrystals and Nanocrystals

Abstract

Lead halide perovskites (LHPs) is the class of semiconductor which shows enormous promise for photovoltaics (PVs) and light emitting diodes (LEDs) as they have excellent and easily tuneable optical properties. Having all those remarkable properties, they still suffer from lead toxicity and stability in ambient conditions. Due to which, their commercial use is difficult. An enormous amount of research has been going on by different research groups in search of lead free halide perovskite. They have come up with lead free double perovskites (DPs), and Cs2AgInCl6 DP is one of them. It has a direct band gap, and are stable and environmentally benign material with 3D perovskite structure. However, the band gap of these material is large (~ 3.3 eV) and so not desirable for optoelectronic applications. One way to achieve typical functionality is by doping optically active metal ions in the lattice of DPs. In this thesis, we show the synthesis and characterization of Ytterbium (Yb) doped Cs2AgInCl6 DPs. Doping of Yb metal ion provides the optical functionality in near infrared region (NIR). We have achieved the doping of Yb in microcrystals as well as colloidal nanocrystals of Cs2AgInCl6 DPs. Our Yb-doped Cs2AgInCl6 DPs show narrow NIR emission (~994 nm, 1.24 eV) by converting UV light absorbed by the host. These Yb-doped Cs2AgInCl6 DPs have millisecond range lifetime corresponding to 2F5/2 → 2F7/2 transition of Yb3+ f electrons. One of the unique feature of these Yb-doped Cs2AgInCl6 DPs is that they do not suffer from self-absorption. Due to that they can emit pure NIR light and can be used in NIR light emitting diodes.