THE APPLICATION OF QUANTUM-WELL SOLAR-CELLS TO THERMOPHOTOVOLTAICS

We discuss the advantages of quantum well solar cells (QWSCs) for ther mophotovoltaic (TPV) applications and illustrate them with InP/lnGaAs and GaInAsP/InGaAs QWSCs which were designed for other applications an d have not been optimised for TPV. It is shown that an InP p-i-n solar cell with 15 lattice matched InGaAs quantum wells (QWs) in the i regi on has an increase in open circuit voltage (V-oc) of (1.7 +/- 0.1) tim es that of a control cell of InP with InGaAs in the i-region under an illuminating spectrum close to that expected from an ideal ytterbia em itter. Also, using an InGaAsP quaternary cell of band gap wavelength o f 1.1 mu m with 60 InGaAs QWs under the same illuminating spectrum the current density is increased by a factor of (2.4 +/- 0.1) over that o f the InP QWSC. The quaternary cell also absorbs longer wavelengths wi thout any significant loss in V-oc. Better temperature coefficients fo r the former quantum well solar cell than the control cell are observe d in a spectrum approximating a black body at 3000 K. Further advantag es of QWs for narrow band and broad band illuminating spectra are disc ussed.