Radiative coupling as a means to reduce spectral mismatch in monolithic tandem solar cell stacks theoretical considerations

Tandem cells currently offer the ability to achieve high conversion efficiencies with prospects for further improvement by increasing the number of cells in the stack. In order to achieve the highest possible efficiencies, studies show that there should be minimal radiative coupling of emitted radiation between cells in the tandem stack. This paper presents theoretical considerations on the performance of two cell tandem stacks under conditions where there is weak and strong radiative coupling between the cells under a range of spectral conditions. Under spectral mismatch conditions, radiative coupling can boost the performance of the worst performing cell, resulting in an efficiency improvement. High radiative coupling may improve the overall performance of tandem cells under conditions where the incident spectrum changes are large, such as for terrestrial applications.