Performance Improvement of the GaSb Thermophotovoltaic Cells With n-Type Emitters (original) (raw)
Related papers
Solar Energy Materials and Solar Cells, 2019
N-type vapor diffusions in p-GaSb wafers is investigated using the group-VI elements S, Se and Te as diffusion sources. The group-VI elements are found difficult to diffuse in bare p-GaSb wafers because they react with Ga atoms to form compounds, thus hindering the diffusion. Deposition of a SiO layer on the p-GaSb surface is found to be crucial for realizing n-type diffusion. With this SiO coating layer, the concentration of group-VI atoms decreased to a low value limiting the reaction with Ga atoms. Se atoms are found to be good n-type diffusion sources. GaSb thermophotovoltaic cells with n-on-p structures are fabricated using Se diffusion. Compared with a traditional GaSb cell with a p-on-n structure, the cell with the n-on-p structure had a higher quantum efficiency at wavelengths beyond 1000 nm. The output power density was also 1.42 times higher compared to the traditional cell when measured with a 1300°C-SiN ceramic IR emitter.
Thermophotovoltaic GaSb Cells Fabrication and Characterisation
For production of highly effective photoconverters semiconductor materials with strictly determined parameters are required. For thermophotovoltaic (TPV) GaSb cells homogeneous Te-doping level of (2-7).1017 cm-3 in the bulk semiconductor is required to produce high efficient PV cells by the Zn diffusion process. In this paper we present data on investigation of the performance of the cells obtained on different GaSb:Te wafers of (100) and (211) orientation. Based on classical I/V measurements and external quantum efficiency (EQE) curves, we analyze cell performances in order to improve all fabrication stages like wafer surface preparation, p-type GaSb emitter elaboration by the zinc diffusion process, antireflection coating deposition and contact realization. Today good performances are obtained on both 3.5 × 3.5 mm2 (211) and 10×10 mm2 (100) GaSb cells. We obtained EQE of 70-76 % in the 800-1600 nm range for the first one and 80-88 % in the same spectrum for the second one. Electri...
Journal of Electronic Materials, 1999
The GaInSb material system is attractive for application in thermophotovoltaic (TPV) cells since its band gap can be tuned to match the radiation of the emitter. At present, most of the TPV cells are fabricated using epitaxial layers and hence are expensive. To reduce the cost, Zn diffusion using elemental vapors in a semiclosed diffusion system is being pursued by several laboratories. In this paper, we present studies carried out on Zn diffusion into n-type (Te-doped) GaSb substrates in an open tube diffusion furnace. The dopant precursor was a 2000Å thick, zinc doped spin-on glass. The diffusion was carried out at temperatures ranging from 550 to 600°C, for times from 1 to 10 h. The diffused layers were characterized by Hall measurements using step-and-repeat etching by anodic oxidation, secondary ion mass spectrometry measurements, and TPV device fabrication. For diffusion carried out at 600°C, the junction depth was 0.3 µm, and the hole concentration near the surface was 5 × 10 19 /cm 3 . The external quantum efficiency, measured without any anti-reflection coating of the TPV cells fabricated using mesa-etching had a maximum value of 38%. Masked diffusion was also carried out by opening windows in a Si 3 N 4 coated, GaSb wafer. TPV cells fabricated on these structures had similar quantum efficiency, but lower dark current.
Thermophotovoltaic Cells on Zinc Diffused Polycrystalline GaSb
2000
For the first time, it has been demonstrated that thermophotovoltaic cells made of polycrystalline GaSb with small grain sizes (down to ∼ 100 x 100 µm) have similar characteristics to the typical Zinc diffused single crystal GaSb cells with identical device parameters. The grain boundaries in polycrystalline GaSb do not degrade TPV cell parameters, indicating that such material can be used for high-efficiency thermophotovoltaic cells.
Thermophotovoltaic Cells Based on Low-Bandgap Compounds
2004
High efficiency TPV GaSb and Ge based cells fabricated by a non-toxic and inexpensive Zn-diffusion technique have been developed. GaSb based cells optimised for operation with solar powered photon emitter allowed increasing the efficiencies up to 27–28% at black body temperature > 2000 K assuming 90% reflection of sub-bandgap photons. Combination of the MOCVD technique or LPE growth and Zn
— An optimized design of a Heterojunction N+ on P GaSb thermophotovoltaic (TPV) cell with hydrogenated amorphous silicon interface passivation is presented. The N+ layer is a transparent conductive oxide (TCO). The interface recombination rate between the p-GaSb and a-Si:H(i) layers is found to have an important effect on cell performance. If this recombination rate can be reduced to 10 5 cm/s, the internal quantum efficiency in the wave range of 600~1700 nm surpasses 95% and the output power density reaches 2W/cm 2 under a given blackbody radiation of 1500K. The high minority carrier electron mobility and diffusion length in the p-GaSb leads to the high internal quantum efficiency. A potential advantage of this cell is its simple cell fabrication process for low cost in high volume manufacturing. Another advantage for this cell for TPV systems is a built in short pass plasma filter with a high reflectivity at longer wavelengths.
Journal of Electronic Materials, 2003
A single-step diffusion followed by precise etching of the diffused layer has been developed to obtain a diffusion pro le appropriate for high-ef ciency GaSb thermophotovoltaic (TPV) cells. The junction depth was controlled through monitoring of light current-voltage (I-V) curves (photovoltaic response) during the post-diffusion emitter-etching process. The measured photoresponses (prior to device fabrication) have been correlated with the quantum ef ciencies (QEs) and the open-circuit voltages in the fabricated devices. An optimum junction depth for obtaining the highest QE and open-circuit voltage is presented based on diffusion lengths (or minority carrier lifetimes), carrier mobility, and the typical diffused impurity pro le in GaSb.
GaSb Crystals and Wafers for Photovoltaic Devices
Journal of Solar Energy Engineering, 2007
GaSb material presents interesting properties for single junction thermophotovoltaic (TPV) devices. GaSb: Te single crystal grown with Czochralski (Cz) or modified Czochralski (Mo-Cz) methods are presented and the problem of Te homogeneity discussed. As the carrier mobility is one of the key points for the bulk crystal, Hall measurements are carried out. We present here some complementary developments based on the material processing point of view: the bulk crystal growth, the wafer preparation, and the wafer etching. Subsequent steps after these are related to the p / n or n/ p junction elaboration. Some results obtained for different thin-layer elaboration approaches are presented. So from the simple vapor phase diffusion process or the liquid phase epitaxy process up to the metal organic chemical vapor deposition process we report some material specificity.
High-efficiency GaSb photocells
Semiconductors, 2013
High current solar cells based on gallium antimonide and intended for use in solar modules and systems with solar spectrum splitting at large solar light concentration ratios, in thermophotovoltaic genera tors with a high temperature emitter, and in laser energy converters have been designed and fabricated by the diffusion of zinc from the gas phase. The influence exerted by the thickness of the p + diffusion layer on the basic characteristics of the solar cell has been studied. The optimal doping profile and the p-n junction depth providing a high photovoltaic conversion efficiency at photocurrent densities of up to 100 A cm-2 have been determined.