Thermal and chemical control of emission and excited-state dynamics in non-(TMS)3P-derived InP quantum dots

Abstract

Here, we present a systematic study of how reaction temperature and indium halide precursor chemistry govern the optical properties of colloidal indium phosphide quantum dots (InP QDs), enabling emission tuning across the visible spectrum (∼530–660 nm) for quantum dot light-emitting diode (QLED) applications. InP QDs were synthesized over a temperature range of 160–300 °C using InHal3 (Hal = Cl, Br, I) as the indium source and tris(diethylamino)phosphine [(DEA)3P] as a non-pyrophoric phosphorus precursor. Across all halides, increasing reaction temperature produces a near-linear red shift in photoluminescence between 180 and 280 °C, with this behavior breaking down at higher temperatures. The extent of wavelength tunability follows the order InCl3 > InBr3 > InI3, with InCl3-derived QDs additionally exhibiting improved monodispersity and reduced photoluminescence quantum yield degradation upon film formation. Optical and structural properties were characterized using photoluminescence and electroluminescence spectroscopy and transmission electron microscopy, alongside systematic evaluation of drop-cast thin films. QLEDs fabricated from QDs of comparable emission wavelength exhibit external quantum efficiencies of 0.05%–0.09%, with devices based on InCl3-derived QDs delivering the highest efficiencies. The absence of a monotonic trend in device performance with halide molecular weight suggests a non-linear relationship between precursor chemistry, excited-state dynamics, and electroluminescent efficiency. Although these efficiencies remain lower than those achieved using (TMS)3P-derived InP QDs, this study demonstrates the viability of environmentally benign aminophosphine-based synthetic routes and highlights the need for device architectures specifically optimized for non-(TMS)3P-derived InP QDs.