The Hot Carrier solar cell has the potential to yield a very high efficiency, well over 50% under 1 sun. Multiple quantum wells have been shown to have significantly slow hot carrier cooling rates than bulk material and are thus a promising candidate for hot carrier solar cell absorbers. However, the mechanism(s) by which hot carrier cooling is restricted is not clear. In this paper is presented a systematic study of carrier cooling rates in GaAs/AlAs MQW with either varying barrier or varying well thickness. These allow an investigation as to whether the mechanisms of either a reduction in hot carrier diffusion; a localisation of phonons emitted by hot carriers; or mini-gaps in the MQW phonon dispersion are primarily responsible for reduced carrier cooling rates. With the conclusion that the interfaces between QW and barrier are primarily responsible for reducing carrier cooling rates through a mechanism of phonon confinement leading to phonon bottleneck restriction of phonon decay and hence re-heating of hot carriers. Some aspects of the consequent affect on the use of MQW as absorbers in a real hot carrier cell are discussed.
Gavin Conibeer, Yi Zhang, Stephen Bremner, and Santosh Shrestha, "Hot carrier cooling mechanisms in multiple quantum wells," Proc. SPIE 10099, Physics, Simulation, and Photonic Engineering of Photovoltaic Devices VI, 100990K (Presented at SPIE OPTO: January 31, 2017; Published: 23 February 2017); https://doi.org/10.1117/12.2251927.
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