Unraveling Quantum Size-Dependent Optoelectrical Phenomena in Hot Carrier Quantum Well Structures

TL;DR

This study explores how quantum confinement in quantum well structures influences hot carrier behavior and optoelectrical properties, revealing that well width affects hot carrier effects and device voltages, with implications for solar cell efficiency.

Contribution

It provides new insights into the impact of quantum well thickness on hot carrier dynamics and optoelectrical properties in heterostructure diodes, advancing understanding for hot carrier solar cells.

Findings

Wider quantum wells exhibit stronger hot carrier effects.

Open-circuit voltage correlates with quantum confinement degree.

Photocurrent mainly generated in the barrier layer.

Abstract

The enhancement of power conversion efficiency beyond the theoretical limit of single-junction solar cells is a key objective in the advancement of hot carrier solar cells. Recent findings indicate that quantum wells (QWs) can effectively generate hot carriers by confining charged carriers within their potential wells and by optimizing material properties. Here, we investigate the impact of quantum confinement on the thermodynamic properties of photogenerated hot carriers in p-i-n InGaAs/InAlAs heterostructure diodes, utilizing QW thicknesses of 4 nm, 5.5 nm, and 7.5 nm. The optical properties of these nanostructures reveal significant hot carrier effects at various lattice temperatures, with a pronounced effect noted at lower temperatures. The experimental results indicate that the widest QW exhibits stronger hot carrier effects than the thinner QWs. Additionally, the open-circuit voltage of the samples demonstrates a correlation with the degree of quantum confinement, mirroring trends observed in the quasi-Fermi level splitting of hot carriers. However, the magnitudes recorded exceed the bandgap of the quantum structures, suggesting that this behavior may be influenced by the barrier layer. Furthermore, the short-circuit current of the samples reveals a strong dependence on excitation power, but not on the degree of quantum confinement. This indicates that the majority of the photocurrent is generated in the barrier, with negligible contributions from photogenerated carriers within the QWs. This study provides insights into the role of quantum confinement on the opto-electrical properties of non-equilibrium hot carrier populations in QW structures.