Enhanced collection efficiencies and performance of interband cascade structures for narrow bandgap semiconductor thermophotovoltaic devices

Abstract

We report on a comparative study of narrow-bandgap (∼0.2 eV at 300 K) thermophotovoltaic (TPV) devices with InAs/GaSb type-II superlattice absorbers. By comparing the characteristics of three narrow bandgap TPV structures with a single absorber or multiple discrete absorbers, it is clearly demonstrated that the device performance of a conventional single-absorber TPV cell is limited mainly by the small collection efficiency associated with a relatively short diffusion length (1.5 μm at 300 K). Furthermore, this study revealed that multi-stage interband cascade (IC) TPV structures with thin individual absorbers can circumvent the diffusion length limitation and are capable of achieving a collection efficiency approaching 100% for photo-generated carriers. Additionally, the open-circuit voltage, the fill factor, the output power, and the power conversion efficiency can be significantly increased in IC TPV devices compared to the conventional single-absorber TPV structure. These results have further validated the potential and advantages of narrow bandgap IC structures for TPV cells.

Near-Field Thermophotovoltaic Conversion with High Electrical Power Density and Cell Efficiency above 14%

“…Our architectures are compatible with more industrial-size implementations involving parallel flat surfaces that were undertaken recently 40 . Recent strategies for designing efficient far-field cells with narrow energy bandgap III-V materials operating at room temperature 41 can also be applied in the near field with frustrated photon modes and will be particularly useful for harnessing energy of medium-grade heat sources.…”

“…Our architectures are compatible with more industrial-size implementations involving parallel flat surfaces that were undertaken recently. 38 Recent strategies for designing efficient far-field cells with narrow energy bandgap III−V materials operating at room temperature 39,40 can also be applied in the near field with frustrated photon modes and will be particularly useful for harnessing energy of medium-grade heat sources. For high-grade heat sources, we have demonstrated the possibility to maintain a temperature difference larger than 1100 K across a small distance (Figure S11), so higher energy bandgap materials used in cells operating at room temperature could also be considered with a careful design for the near field.…”

Interfacial Intermixing and Its Impact on the Energy Band Structure in Interband Cascade Infrared Photodetectors

“…In the ICIP structures, the absorber thickness of each stage is designed to be shorter than the diffusion length to ensure the efficient collection of photogenerated carriers. Therefore, the incident photons can be effectively absorbed without being restricted by diffusion length even at a high temperature. , Moreover, the multiple-stage structure using thin absorbers can significantly increase the detector resistance and suppress thermal noise . All these aspects make ICIPs ideal structures for high-performance and high-operation temperature infrared detectors.…”

Performance analysis of narrow-bandgap interband cascade thermophotovoltaic cells

“…A very high open-circuit voltage (e.g. >0.5 V) was achieved even with a bandgap as low as 0.2 eV at 300 K [20][21][22][23][24][25][26], and a conversion efficiency of 9.6% was measured at 300 K for a 3-stage device with a 0.4 eV bandgap [24].…”