Two-Color Photoexcitation in a GaNAs/AlGaAs Quantum Well Solar Cell

Abstract

We demonstrate an efficient two-color photoexcitation process in a GaNAs/AlGaAs multiple quantum well (MQW) solar cell. The introduction of N into the GaAs MQW induces a marked reduction in bandgap energy, forming a large conduction band offset, and the formation of localized states. Owning to this deep confinement, the thermal escape of photogenerated carriers from the QWs is greatly suppressed even at room temperature, resulting in a reduction in photocurrent. An additional photocurrent is generated by a two-color absorption process of sub-bandgap photons.

A substrate removal processing method for III–V solar cells compatible with low-temperature characterization

“…In our group, we have been working for many years on novel solar cell concepts [20,21] using semiconductor quantum dots as absorbing material. Similarly to the case of quantum dot [22] and quantum well photodetectors [23], lowtemperature characterization, in particular photocurrent experiments, has been essential to understand the fundamental principles, potential and limitations of solar cells using inorganic nanostructures [24][25][26]. As previously mentioned, one hot topic on this kind of solar cells is to enhance the absorptivity of the quantum structures by using light trapping mechanisms in thin-film devices.…”

Direct Observation of Two-Step Photon Absorption in an InAs/GaAs Single Quantum Dot for the Operation of Intermediate-Band Solar Cells

“…This process has been demonstrated to date with ensembles of QDs at low temperature and room temperature by measuring an increase in photocurrent when two sub-bandgap energy photons are simultaneously absorbed. Other groups have also studied the two-step photon absorption using an ensemble of QDs, − but the direct demonstration of two-step photon absorption remains a challenge due to size, composition, and shape inhomogeneities in ensembles of QDs. In addition, the fundamental mechanism of carrier extraction from a QD has not been fully understood.…”