Theoretical analysis of non-radiative multiphonon recombination activity of intrinsic defects in CdTe

Abstract

We present an analysis of recombination activity of intrinsic defects (VCd, TeCd, VTe, and Tei) in CdTe based on the multiphonon single-mode carrier-capture model, with vibronic parameters obtained using hybrid density functional theory. This analysis allows us to determine the defects and the corresponding electronic processes that have high trapping rates for electrons, for holes, or for both. The latter, being potentially the most active recombination centers, decreases the carrier lifetime in the absorber layer of a CdTe solar cell. Taking into account the relatively high calculated capture cross-sections of the TeCd antisite defect (σ = 8.7× 10−15 cm2 for electron capture on TeCd+2 defect, σ = 6.8 × 10−14 cm2 for hole capture on TeCd+1 defect at room temperature) and its deep trapping level (0.41 eV for +2/+1 level), we conclude that this defect is the most active recombination center among the intrinsic defects in p-type CdTe. Other processes that do not lead to effective recombination are: (i) fast hole capture on Tei+1 defect (σ = 1.1 × 10−13 cm−2), (ii) electron capture on TeCd+1 defect (σ = 2.9 × 10−15 cm−2), (iii) somewhat slower hole capture on TeCd0 defect (σ = 9.4 × 10−20 cm−2), (iv) hole capture on VCd−1 defect (σ = 7 × 10−19 cm2), and (v) electron capture on Tei+1 defect (σ = 4.4 × 10−19 cm−2). The cross-sections are found to be negligibly small for the remaining capture processes.