# Refractory All-Ceramic Thermal Emitter for High-Temperature Near-Field Thermophotovoltaics

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## Abstract

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## 1. Introduction

## 2. Theoretical Fundamentals for Analyzing Near-Field TPVs

## 3. Results and Discussion

## 4. Conclusions

## Author Contributions

## Funding

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 1.**Schematic of the near-field TPV system, consisting of a refractory selective thermal emitter and a SiC/Si tandem cell. The thermal emitter consists of B${}_{4}$C gratings with three different substrates: B${}_{4}$C (Case 1), SiC (Case 2) and BeO (Case 3). The grating period $\Lambda $ and the width w are 50 nm and 10 nm, respectively. The temperature of the thermal emitter is maintained at 2000 ${}^{\circ}$C, while the PV cell works at 400 ${}^{\circ}$C. The separation gap d is kept as 100 nm, and the thicknesses of each layer are as follows: ${h}_{1}=200$ $\mathsf{\mu}$m, ${h}_{2}=2$ $\mathsf{\mu}$m, ${h}_{3}=50$ nm and ${h}_{4}=50$ nm.

**Figure 2.**(

**a**) Refractive indices (n) and extinction coefficients ($\kappa $) of SiC and BeO. (

**b**) Refractive indices (n) and extinction coefficients ($\kappa $) of B${}_{4}$C and B${}_{4}$C grating with filling ratio of 0.2, including TE and TM polarizations.

**Figure 3.**(

**a**) Emissivity of the three thermal emitter cases. The yellow dashed line represents the EQE of the SiC/Si cell. (

**b**) Spectral heat fluxes (dashed lines) as the separation gap is 100 nm and the corresponding spectral output power (solid lines) from the PV cell. From left to right, the two figures in each column correspond to scenario 1, 2 and 3, respectively. Case 1: B${}_{4}$C/B${}_{4}$C, Case 2: B${}_{4}$C/SiC, and Case 3: B${}_{4}$C/BeO.

**Figure 4.**(

**a**) Total heat fluxes (dashed lines) and output power (solid lines) as a function of the separation gap. (

**b**) Variation in conversion efficiency against the separation gap. These results are based on scenario 2.

**Table 1.**Parameters for the TPV system based on scenario 2 (${h}_{3}={h}_{4}=50$ nm, $w/\Lambda =0.2$), including short circuit current ${I}_{\mathrm{SC}}$, open circuit voltage ${V}_{\mathrm{OC}}$, fill factor (FF), total heat flux q, output power P and conversion efficiency $\eta $. The separation gap is 100 nm.

Emitter | ${\mathit{I}}_{\mathbf{SC}}$ | ${\mathit{V}}_{\mathbf{OC}}$ (V) | FF (%) | q | P | $\mathit{\eta}$ (%) |
---|---|---|---|---|---|---|

(A m${}^{-2}$, $\times {10}^{4}$) | (W m${}^{-2}$, $\times {10}^{5}$) | (W m${}^{-2}$, $\times {10}^{4}$) | ||||

Case 1 (B${}_{4}$C/B${}_{4}$C) | 7.74 | 1.19 | 81.08 | 6.34 | 7.45 | 11.74 |

Case 2 (B${}_{4}$C/SiC) | 6.26 | 1.17 | 80.94 | 3.97 | 5.95 | 14.96 |

Case 3 (B${}_{4}$C/BeO) | 3.47 | 1.14 | 80.54 | 1.29 | 3.19 | 24.69 |

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**MDPI and ACS Style**

Chen, F.; Liu, X.; Tian, Y.; Goldsby, J.; Zheng, Y.
Refractory All-Ceramic Thermal Emitter for High-Temperature Near-Field Thermophotovoltaics. *Energies* **2022**, *15*, 1830.
https://doi.org/10.3390/en15051830

**AMA Style**

Chen F, Liu X, Tian Y, Goldsby J, Zheng Y.
Refractory All-Ceramic Thermal Emitter for High-Temperature Near-Field Thermophotovoltaics. *Energies*. 2022; 15(5):1830.
https://doi.org/10.3390/en15051830

**Chicago/Turabian Style**

Chen, Fangqi, Xiaojie Liu, Yanpei Tian, Jon Goldsby, and Yi Zheng.
2022. "Refractory All-Ceramic Thermal Emitter for High-Temperature Near-Field Thermophotovoltaics" *Energies* 15, no. 5: 1830.
https://doi.org/10.3390/en15051830