Temperature-dependent Optoelectronic Properties of Quasi-2D Colloidal Cadmium Selenide Nanoplatelets

摘要

Colloidal Cadmium Selenide (CdSe) nanoplatelets (NPLs) are a recentlydeveloped class of efficient luminescent nanomaterial suitable foroptoelectronic device applications. A change in temperature greatly affectstheir electronic bandstructure and luminescence properties. It is important tounderstand how-and-why the characteristics of NPLs are influenced, particularlyat elevated temperature, where both reversible and irreversible quenchingprocesses come into picture. Here we present a study on the effect of elevatedtemperature on the characteristics of colloidal CdSe NPLs. We used aneffective-mass envelope function theory based 8-band k$\cdot$p model anddensity-matrix theory considering exciton-phonon interaction. We observed thephotoluminescence (PL) spectra at various temperatures for their photonemission energy, PL linewidth and intensity by considering the exciton-phononinteraction with both acoustic and optical phonons using Bose-Einsteinstatistical factors. With rise in temperature we observed a fall in thetransition energy (emission redshift), matrix element, Fermi factor and quasiFermi separation, with reduction in intraband state gaps and increasedinterband coupling. Also, there was a fall in the PL intensity, along withspectral broadening due to an intraband scattering effect. The predictedtransition energy values and simulated PL spectra at varying temperaturesexhibit appreciable consistency with experimental results. Our findings haveimportant implications for application of NPLs in optoelectronic devices, suchas NPL lasers and LEDs, operating much above room temperature.