Hot carrier dynamics in Quantum Well Solar Cells (Thermal Photon Gain)*

Quantum well solar cells (QWSCs) have been shown to inhibit hot carrier thermalization relative to bulk materials and have therefore stimulated significant interest as a potential absorber region in third generation hot carrier solar cells. Investigations of high quality InGaAs/GaAsP QWs in GaAs p-i-n solar cells have recently alluded to the possibility of hot carrier extraction in device structures through the measurement of a diode ideality factor of n < 1. In order to prove the carriers extracted in these systems are in fact “hot,” simultaneous current density-voltage (JV) and photoluminescence (PL) measurements are performed to directly compare the carrier dynamics and photovoltaic performance in such devices. Several transitions complicate the PL spectra of QWs making determination of the carrier temperature via fitting of the high energy tail using simple Planck’s law methods insufficient. Therefore, full spectral fitting is performed in order to extract the carrier temperature while considering the occupation of higher energy states in the QWs, which is then related to ideality factor determined in electrical measurements.