The schematic energy flow of standard and solar thermophotovoltaic (STPV) systems. In standard solar cells, a PV cell is directly illuminated by the sun. Whereas in STPV systems (b), an absorber placed between the sun and PV cell is heated by absorbing the broad solar spectrum. A thermal emitter connected to the absorber converts the heat into narrowband thermal radiation that illuminates the PV cell. The inset represents the schematic of the multilayer broadband absorber device.