Non-Radiative Carrier Recombination Enhanced by Two-Level Process: A First-Principles Study

Abstract

Non-radiative recombination plays an important role in the performance of optoelectronic semiconductor devices such as solar cells and light-emitting diodes. Most textbook examples assume that the recombination process occurs through a single defect level, where one electron and one hole are captured and recombined. Based on this simple picture, conventional wisdom is that only defect levels near the center of the bandgap can be effective recombination centers. Here, we present a new two-level recombination mechanism: first, one type of carrier is captured through a defect level forming a metastable state; then the local defect configuration rapidly changes to a stable state, where the other type of carrier is captured and recombined through another defect level. This novel mechanism is applied to the recombination center in CdTe. We show that this two-level process can significantly increase the recombination rate (by three orders of magnitude) in agreement with experiments. We expect that this two-level recombination process can exist in a wide range of semiconductors, so its effect should be carefully examined in characterizing optoelectronic materials.

Self-compensation in chlorine-doped CdTe

“…Interestingly, the V Cd ( C 2 v ) in the neutral charge state exhibits a ground-state configuration with all the valence band filled and all the conduction bands empty. This result is in close agreement with recent DFT-HSE06 calculations, although the formation of the Te-Te dimer was not reported 42 . On the other hand, the V Cd ( D 2 d ) structure reveals the formation of two Te-Te dimers with bond distances of 2.765 Å, while its electronic structure indicates a double donor character.…”

Understanding the role of selenium in defect passivation for highly efficient selenium-alloyed cadmium telluride solar cells

“…Functional Theory (DFT) modelling has shown act as harmful recombination centres [28], [29]. We suggest that these defects can be passivated or made less likely to form when selenium is present, with an increasing passivation effect for concentrations of selenium up to 10 -11 at%.…”

Microscopic insight into non-radiative decay in perovskite semiconductors from temperature-dependent luminescence blinking

“…On the other hand, as suggested by some of us 23 , efficient quenching could also arise from a complex of several defects, which are otherwise harmless individually. Such a complex can provide an efficient non-radiative decay channel by creating several energy levels inside the band gap 57,58 . For example a complex between a shallow electron and shallow hole trap can work as efficient non-radiative center (Fig.…”