Effects of Matching Short Current Density for Dual Junction Lead Salts TPV Device at 1400 C⁰

Thermophotovoltaic (TPV) device that can be efficiently used to convert thermally stored energy in molted silicon at 1400 C0 cells to electrical energy has been studied. The device utilizes Pb0.8 Sr0.2 Se/ Pb0.81 Sn0.19 Se /Pb0.8 Sr0.2 Se IV-VI material in a multiple quantum well configuration two junction device structure. Using quantum well calculations and including strain effects the interband optical transition energy gaps (well widths) were calculated to be 450 meV(3.5nm), and 343 meV(4.9nm), for the top and bottom junctions, respectively. We calculated the short current density, output electric power density and efficiency for each junction as a function of device thickness. The overall maximum electric power density and efficiency for the device was 3.46 W/cm2 and 26.7% at device thickness of 6.0 $\mu$m; however the short current density for both junctions was not matched. In order to do this and stabilize the device performance, we optimized the junction layers n and p thickness values. As a result, the device maximum output electrical power and efficiency dropped to 3.05 W/cm2 and 16.89% at device thickness values of 3.65 and 9.95 $\mu$m. At these values, the matched short circuit current density is 11.55 A/cm2. It is shown that multiple quantum well single junction design for the above material system suffice to obtain better efficiency and output electric power compared to designs using the same bulk material system.