Dispersive photoluminescence decay by geminate recombination in amorphous semiconductors

TL;DR

This paper investigates the power-law decay of photoluminescence in amorphous semiconductors, deriving a relation between decay exponent and dispersive transport, aligning theory with experimental observations.

Contribution

It introduces a simple relation linking the decay exponent to dispersive transport parameter, enhancing understanding of recombination dynamics in amorphous semiconductors.

Findings

Derived the relation delta = 1 + alpha/2 between decay exponent and dispersive transport.

Confirmed that the amplitude of decay matches experimental measurements in a-Si:H.

Showed that dispersive transport influences geminate recombination rates.

Abstract

The photoluminescence decay in amorphous semiconductors is described by power law $t^{-delta}$ at long times. The power-law decay of photoluminescence at long times is commonly observed but recent experiments have revealed that the exponent, $delta sim 1.2-1.3$, is smaller than the value 1.5 predicted from a geminate recombination model assuming normal diffusion. Transient currents observed in the time-of-flight experiments are highly dispersive characterized by the disorder parameter $alpha$ smaller than 1. Geminate recombination rate should be influenced by the dispersive transport of charge carriers. In this paper we derive the simple relation, $delta = 1+ alpha/2 $. Not only the exponent but also the amplitude of the decay calculated in this study is consistent with measured photoluminescence in a-Si:H.