Lead-Free Stable Wide-Band-Gap Double Perovskite with Absorption in the Visible Region

A semiconductor double perovskite oxide Y 2 CuTiO 6 with a wide band gap was synthesized by solid-state reaction. The compound was characterized by x-ray diffraction, scanning electron microscopy, energy-dispersive x-ray spectroscopy, thermogravimetric analysis, UV–visible diffuse reflectance spectroscopy, photoluminescence excitation and emission spectroscopy. Rietveld refinement of x-ray diffraction pattern using the General Structure Analysis System-II indicated a hexagonal structure with space group P6 3 cm (#185) with lattice parameters a = b = 6.199(2) Å and c = 11.516(4) Å. Trigonal bi-pyramidal Ti(IV)/Cu(II)O 5 is arranged randomly in the B sites of Y 2 CuTiO 6 . Microscopic measurements confirmed a dense microstructure with Y:Cu:Ti = 2:1:1. Thermogravimetric analysis showed high thermal stability of this compound, which is desired for optical applications. UV–VIS DRS spectra displayed wide band absorption in the visible region with a band gap of 2.98 eV as commonly seen in wide-band-gap semiconductors. From the photoluminescence excitation spectra, maximum excitation was observed around 365 nm, so the compound was excited by a 355 nm laser to study the emission properties. A broad emission spectrum is observed in the visible range from the photoluminescence emission study. The lead-free double perovskite with high material stability against temperature showing huge absorption and emission in the visible region without any intrinsic doping is unique and interesting for a wide range of applications. Graphic Abstract