Spectral properties of photogenerated carriers in quantum well solar cells

TL;DR

This paper develops a microscopic Green's function-based theory to analyze how quantum confinement in quantum well solar cells affects carrier spectral properties, revealing challenges in carrier escape efficiency.

Contribution

It introduces a detailed quantum transport model to study carrier dynamics in quantum well solar cells, highlighting effects of quantum confinement on spectral response and carrier escape.

Findings

Deep level carrier escape can be inefficient at room temperature.

Quantum confinement significantly alters the spectral properties of carriers.

The theory provides insights into non-equilibrium carrier distributions in quantum wells.

Abstract

The use of low-dimensional structures such as quantum wells, wires or dots in the absorbing regions of solar cells strongly affects the spectral response of the latter, the spectral properties being drastically modified by quantum confinement effects. Due to the microscopic nature of these effects, a microscopic theory of absorption and transport is required for their quantification. Such a theory can be developed in the framework of the non-equilibrium Green's function approach to semiconductor quantum transport and quantum optics. In this paper, the theory is used to numerically investigate the density of states, non-equilibrium occupation and corresponding excess concentration of both electrons and holes in single quantum well structures embedded in the intrinsic region of a p-i-n semiconductor diode, under illumination with monochromatic light of different energies. Escape of carriers from the quantum well is considered via the inspection of the spectral photocurrent at a given excitation energy. The investigation shows that escape from deep levels may be inefficient even at room temperature.