Hot carriers and thermalization properties of type-II In As/AlAsSb MQW and superlattice solar cells

Thermalization of photo-generated hot carriers via phonon mediated relaxation pathways is one of the main loss mechanisms in photovoltaic devices. Energy loss via hot carrier thermalization can be suppressed if the exchanged energy between hot carriers and phonons (mainly optical in polar semiconductors) is not transferred to low energy acoustic phonons (heat dissipation). In this study, the effects of barrier thickness in thermalization of hot carriers of InAs multi-quantum well (MQW) type-II structures are investigated. Experimental and theoretical results indicate that by increasing the thickness of the barrier – the hot carrier thermalization reduces. This effect is associated with the reduction of the Klemens mechanism via the increase of the phononic bandgap in the structure of the superlattice.