Recombination dynamics of photoluminescence (PL) in colloidal CdSe/ZnS quantum dots (QDs) were studied using time-resolved PL measurements. The PL intensity shows a biexponential decay at 9 K, consisting of a fast component (∼1 ns) and a slow component (∼6.3 ns). Based on the emission-energy and temperature dependence of carrier lifetimes, we suggest that the fast and slow PL decay of colloidal CdSe/ZnS QDs originates from recombination of the delocalized carriers in the internal core states and the localized carriers at the interface, respectively.

We report the distance-dependent energy transfer from an InGaN quantum well to graphene oxide (GO) by time-resolved photoluminescence (PL). A pronounced shortening of the PL decay time in the InGaN quantum well was observed when interacting with GO. The nature of the energy-transfer process has been analyzed, and we find the energy-transfer efficiency depends on the 1/d² separation distance, which is dominated by the layer-to-layer dipole coupling.

The authors studied the concentration dependence of carrier localization in InN epilayers using time-resolved photoluminescence (PL). Based on the emission-energy dependence of the PL decays and the PL quenching in thermalization, the localization energy of carriers in InN is found to increase with carrier concentration. The dependence of carrier concentration on the localization energy of carriers in InN can be explained by a model based on the transition between free electrons in the conduction band and localized holes in the deeper tail states. They suggest that carrier localization originates from the potential fluctuations of randomly located impurities.

Spatially-resolved electroluminescence (EL) images in the triple-junction InGaP/InGaAs/Ge solar cell have been investigated to demonstrate the subcell coupling effect. Upon irradiating the infrared light with an energy below bandgap of the active layer in the top subcell, but above that in the middle subcell, the EL of the top subcell quenches. By analysis of EL intensity as a function of irradiation level, it is found that the coupled p-n junction structure and the photovoltaic effect are responsible for the observed EL quenching. With optical coupling and photoswitching effects in the multi-junction diode, a concept of infrared image sensors is proposed.

We studied the optical and electrical properties of InN epilayers with rapid thermal annealing (RTA). The intensity of the photoluminescence (PL) and the carrier mobility were found to increase as the temperature of RTA was increased. We suggest that the formation of compensating acceptors (indium vacancies) after RTA is responsible for the improvement of the quality in InN. The dependence of the PL emission peak on carrier concentration provides a possible method for estimating the carrier concentration in degenerate InN.