Hot carrier solar cells have a fundamental efficiency limit well in excess of single junction devices. Developing a
hot carrier absorber material, which exhibits sufficiently slow carrier cooling to maintain a hot carrier population
under realistic levels of solar concentration is a key challenge in developing real-world hot carrier devices.
We propose strain-balanced In0.25GaAs/GaAsP0.33 quantum wells as a suitable absorber material and present
continuous-wave photoluminescence spectroscopy of this structure. Samples were optimised with deep wells and
the GaAs surface buffer layer was reduced in thickness to maximise photon absorption in the well region. The
effect of well thickness on carrier distribution temperature was also investigated. An enhanced hot carrier effect
was observed in the optimised structures and a hot carrier distribution temperature was measured in the thick
well (14 nm) sample under photon flux density equivalent to 1000 Suns concentration.
Luminescent concentrator (LC) plates with different dyes were combined with standard multicrystalline silicon solar cells. External quantum efficiency measurements were performed, showing an increase in electrical current of the silicon cell (under AM1.5, 1 sun conditions, at normal incidence) compared to a bare cell. The influence of dye concentration and plate dimensions are addressed. The best results show a 1.7 times increase in the current from the LC/silicon cell compared to the silicon cell alone. To broaden the absorption spectrum of the LC, a second dye was incorporated in the LC plates. This results in a relative increase in current of 5-8% with respect to the one dye LC, giving. Using a ray-tracing model, transmission, reflection and external quantum efficiency spectra were simulated and compared with the measured spectra. The simulations deliver the luminescent quantum efficiencies of the two dyes as well as the background absorption by the polymer host. It is found that the luminescent quantum efficiency of the red emitting dye is 87%, which is one of the major loss factors in the measured LC. Using ray-tracing simulations it is predicted that increasing the luminescent quantum efficiency to 98% would substantially reduce this loss, resulting in an increase in overall power conversion efficiency of the LC from 1.8 to 2.6%.
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