Unveiling the uncommon blue-excitable broadband yellow emission from self-trapped excitons in a zero-dimensional hybrid tellurium-based double perovskite

Mao, Y., Zhang, J., Ren, Q., (...), Zhou, G., Zhang, X.-M.// Journal of Materials Chemistry C//

DOI https://doi.org/10.1039/D2TC03150G

Low-dimensional metal halides with ns2 lone-pair electrons have been recognized as new generation luminescent emitters for various optoelectronic applications. However, 5s2 configuration tellurium halides have not received substantial attention despite their fascinating photoluminescence (PL) properties. Here, a hybrid tellurium-based double perovskite of (C20H20P)2TeCl6 is developed, in which the [TeCl6]2− octahedra are completely surrounded by [C20H20P]+ organic cations to form a unique zero-dimensional (0D) “host–guest” structure. An uncommon broadband yellow emission peaking at 570 nm with ultra-broad excitation from ultraviolet to blue light is excavated, which originates from the triplet self-trapped exciton (STE) emission of Te4+. Moreover, the 5s2 electronic transition mechanism of Te4+ is systematically revealed in depth, benefiting from the temperature-dependent fluorescence dynamic analysis and auxiliary theoretical calculations. It is concluded that the distortion degree of the [TeCl6]2− octahedron comprehensively affects the full width at half-maximum (FWHM) (positive correlation), Stokes shift (negative correlation) and PL intensity (negative correlation) with increasing temperatures. This work sheds new light on the PL behaviour of Te4+ and opens up a feasible avenue for blue-excitable broadband emissions in low-dimensional organic–inorganic hybrid double perovskites.