Papers by Author: Tzer En Nee

Abstract: The result of an extensive research on this material is the achievement of approaching 20% efficiency by the co-evaporation of copper, indium, gallium and selenium elements. Recently, photoluminescence (PL) spectra have been studied on Cu (In,Ga) Se₂ (CIGS) thin films and CIGS solar cells, to clarify the carrier recombination process. The CIGS layers were grown on the Mo-coated soda-lime glass substrate by the three stage process and four sources co-evaporation of constituent elements onto a heated substrate. It has found that the structural and optical properties of the CIGS thin film was influenced by the Cu/Ga ratio (R_Cu/Ga) of the CIGS thin film compositional variation. The X-ray diffraction and PL spectra were used to characterize the structure property and carrier recombination mechanism of CIGS thin film.

Abstract: The temperature dependence of the photoluminescence (PL) emission spectra of self-organized InAs/GaAs quantum dots (QDs) grown under different growth conditions in the range 20-300K has been investigated. Three InAs QD samples were grown on (100) 2º-tilted toward (111)A Si-doped GaAs substrates by metal-organic chemical vapour epitaxy (MOVPE), with various size uniformities and dot densities. Observing the measured PL spectra at 20K, the differences caused by size uniformities among the three samples were obvious. The PL spectra were simulated with rate equations, taking into account the carrier relaxation between the first excited state and the ground state. Interestingly, the calculated relaxation lifetimes at 20K were 198ps, 139ps and 54ps for the samples. The temperature dependent PL spectra were also simulated using the same model. Based on the calculated values of temperature dependent relaxation lifetimes, the differences in changes with temperature among the three samples are discussed. The results are consistent with the thermal redistribution effect.