Temperature and voltage-bias dependent two-step photon absorption in InAs/GaAsl Al0.3GaAs quantum dot in a well solar cells

The realization of the concept of the intermediate band solar cell (IBSC) requires that two-step photon absorption dominates at room temperature. To increase two step photon absorption (TSPA), an InAs/GaAs/Al
_0.3
GaAs quantum dot in a well (Dwell) structure is used to reduce thermal escape of carriers. The Dwell structure shows decreased TSPA with increasing temperature because of faster thermal escape. With an increased electron ground state barrier height relative to Al
_0.3
GaAs, the observable TSPA occurs up to 80K. The extracted thermal activation energy from temperature dependent TSPA is between 80-95 me V, which is associated with holes escape processes. Charge separation along the growth direction reduces the recombination rate in the IB. The stable TSPA observed at -2V reverse bias may be a balance between the reduced recombination rate and increased tunneling rate.