A thermophotovoltaic (TPV) system that can convert thermal radiation from terrestrial heat sources into electricity, plays an important role in energy utilization, waste heat recovery and so on. In order to enhance the conversion efficiency of a TPV system having a narrow-band thermal emitter, we propose to add a back gapped reflector (BGR) to recover more out-of band (OOB) photons. We first design a Tamm plasmon thermal emitter to yield a narrow-band emission peak matching well with the bandgap of the InGaAs cell. Then, we add a BGR on the PV cell to regulate the absorption spectrum of the cell. Results show that, compared to the back surface reflector (BSR), the TPV system with the Au BGR cell has a higher power conversion efficiency (PCE), because more OOB photons are reflected back to the emitter by the Au BGR cell, so that the absorbed power by the cell decreases while the output power is improved. Due to the contribution of recycled OOB photons, at 1500 K, a 1.7 % OOB reflectance gain of the BGR (h = 0.2 μm, t = 1.2 μm) can actually increase the PCE by about 4 %. In addition, a thin PV cell and an appropriately thick air gap layer of 0.4–0.6 μm are suggested to obtain a high η × Pout. The PCE of the TPV system based on the Tamm plasmon emitter is higher and becomes saturated at a lower temperature than the broad-band SiC emitter. This work may facilitate high-performance TPV energy conversion.
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