A photoluminesence (PL) study of the radiative recombination mechanisms for CdTe films deposited under different Cd and Te overpressure by elemental vapor transport is presented. The experiment and analysis have been carried out in the temperature range of 12-130K. The intensity of the PL laser excitation beam was varied by two orders of magnitude. It has been established that the bands in the 1.47-1.50 eV are determined by transitions involving shallow D and A states and the 1.36x-1.37x eV band is due to band to level transitions. Deep transitions at 1.042 eV and 1.129 eV are due to radiative transitions to levels determined by CdTe native defects.
T he effect of the vapor phase Cadmium (Cd) to Tellurium (Te) ratio on the electronic properties of CdTe films is being studied. The stoichiometry of CdTe films is being altered by varying the gas phase Cd/Te ratio during the Elemental Va por Transport (EVT) deposition process. Resistivity-temperature measurements and solar cells made with polycrystalline EVT CdTe suggest changes in the native cadmium vacancy (V Cd) concentration and carrier lifetime. The findings are in good agreement with the recently updated defect levels using the HSE approximation. Photoluminescence (PL) analysis has also demonstrated variation in the formation of defect complexes with the Cd/Te ratio. 2-Photon TRPL lifetime measurements showed improved minority-carrier lifetime for CdCh treated samples deposited at low Cd/Te ratios.
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