摘要:

Strain‐compensated Quantum Well Cells (QWCs) have been shown to extend the absorption to longer wavelengths than attainable with lattice‐matched material, while retaining a similar or better dark current. This is of particular interest for thermophotovoltaic (TPV) applications with low temperature sources where low energy bandgaps are required, for example in combination with a Holmia emitter of 1.95 &mgr;m peak emission. Here we report on a two quantum well In0.74Ga0.26As/In0.36Ga0.64As device which absorbs out to 2040 nm, as observed by cathodoluminescence. Our modelling of the spectral response, including quantum and strain effects, is also consistent with this result. We show that the material quality measured by transmission electron microscopy (TEM) is excellent, exhibiting sharp interfaces. However, the electrical properties under illumination are less encouraging: At room temperature not all carriers are collected in forward bias. We present results on the field and temperature dependence of carrier escape and collection. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1539389

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

We report on the design, fabrication and evaluation of InGaAs/InP TPV cells. The fabrication process was developed for single wafer laboratory processing of lattice matched In0.53Ga0.47As cells and subsequently adapted for batch processing in industry. The 1 × 1cm cells and 1mm diameter mesa structures were evaluated using Dark IV and the PVIV techniques. Of the batch (volume) processed 1 × 1 cm cells, the best measured efficiency under AM0 conditions (Si standard) was 10.9&percent; (batch efficiency was 10.4&percent;), with a short circuit current density (ISC) of 54.6 mA/cm2, open‐circuit voltage (VOC) of 363 mV and a fill factor (FF) of 74&percent;. Using an IR lamp, a current density of 1442.8 mA/cm2, open‐circuit voltage of 418.5 mV and a fill factor of 65.7&percent; were recorded. We also point out the salient design and fabrication features employed in realising the above quoted results, which we believe, are the first reported results from an industrial volume production. Problems associated with volume production are also discussed with solutions. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1539390

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

A new method for developing a realistic model of any type of solar cell, with application to Thermophotovoltaic devices, is presented in this paper. Taking into account the high cost of research and experimentation involved with the development of advanced cells, we present here this novel methodology. An example model of an InGaP/GaAs/Ge multi‐junction cell is prepared and is fully simulated. The major stages of the process will be explained and the simulation results are compared to published experimental data. An example of cell parameters optimization is also presented. The flexibility of the proposed methodology is demonstrated and example results are shown throughout the whole process. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1539391

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

The simultaneous diffusion of Zn and P into InGaAs and GaSb from a local vapour phase source was investigated. Zn diffusion allowed to form a TPV cells withp‐layer (emitter) of 0.2–0.6 &mgr;m thickness without any additional post‐diffusion operations. The penetration depth of Zn was determined by temperature and time of diffusion and was found to depend on defects and impurities at the InP/InGaAs heterointerfaces. This interface acts as a source of nonequilibrium neutral interstitials. We assume that the growth of thin undoped InP before the growth of InGaAs base region can decrease induced defects. This is recommended for an efficient suppression of the anomalous fast Zn diffusion. Doping profiles of thep‐layers were obtained from the Raman spectra of the cell structure and by the Secondary Ion Mass Spectroscopy method. Good performance characteristics were demonstrated for InGaAs and GaSb TPV cells based on this technique. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1539392

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

P‐GaAs/p‐Ge/n‐Ge heterostructures with a submicron (0.1 &mgr;m) GaAs window for the thermophotovoltaic (TPV) application have been fabricated using the combination of LPE and Zn‐diffusion techniques. Due to the increase of the open circuit voltage by growth of a GaAs wide bandgap window, an increase of efficiency of Ge based TPV cells from 2.6 – 4.8&percent; up to 3.1 – 6.1 &percent; takes place for the emitter temperature in the range of 1400 – 1900 K. The efficiencies higher than 13&percent; under the cut‐off at &lgr;<900 nm AM0 solar spectrum have been achieved in photovoltaic (PV) concentrator cells with a GaAs window layer at photocurrent densities of 3–25 A/cm2. By means of LPE growth and Zn diffusion techniques, TPV cells based onp‐InAsSbP/n‐InAsSbP/n‐InAs structures were fabricated sensitive in the infrared range of 2.5–3.4 &mgr;m. Lattice‐matched InAsSbP (Eg=0.45–0.48eV) quaternary alloy layers were grown on the (100) InAs substrates at 850 K by the step‐cooling LPE technique. Low‐temperature (600–630 K) pseudo‐closed box Zn diffusion was used to producep‐njunctions in InAsSbP and InAs. Developed InAsSbP‐based TPV cells demonstrate rather good perfomance, which can be improved by the structure optimisation. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1539393

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

This paper presents results of experimental and theoretical research on antimonide‐ based thermophotovoltaic (TPV) materials and cells. The topics discussed include: growth of large diameter ternary GaInSb bulk crystals, substrate preparation, diffused junction processes, cell fabrication and characterization, and, cell modeling. Ternary GaInSb boules up to 2 inches in diameter have been grown using the vertical Bridgman technique with a novel self solute feeding technique. A single step diffusion process followed by precise etching of the diffused layer has been developed to obtain a diffusion profile appropriate for high efficiency, p‐n junction GaSb and GaInSb thermophotovoltaic cells. The optimum junction depth to obtain the highest quantum efficiency and open circuit voltage has been identified based on diffusion lengths (or minority carrier lifetimes), carrier mobility and experimental diffused impurity profiles. Theoretical assessment of the performance of ternary (GaInSb) and binary (GaSb) cells fabricated by Zn diffusion in bulk substrates has been performed using PC‐1D one‐dimensional computer simulations. Several factors affecting the cell performances such as the effects of emitter doping profile, emitter thickness and recombination mechanisms (Auger, radiative and Shockley‐Read‐Hall), the advantages of surface passivation and the impact of dark current due to the metallic grid will be discussed. The conditions needed for diffused junction cells on ternary and binary substrates to achieve similar performance to the epitaxially grown lattice‐ matched quaternary cells are identified. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1539394

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

This paper reviews recent results of the study of Zn diffusion from the vapor phase in important thermophotovoltaic (TPV) materials such as GaSb‐, InGaAsSb‐, InGaSb‐ and InAsSbP. Peculiarities of Zn diffusion in each of these materials and different ways of tailoring the Zn diffusion profile for fabrication of optimized emitters in TPV cells are discussed. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1539395

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

Recent improvements in large area, high efficiency, monolithic interconnected modules (MIMs) represent a significant step in the development of thermophotovoltaic (TPV) technology for various power producing applications. The MIM architecture with transmissive integrated spectral control offers a desirable high‐voltage, low‐current output, front‐side contacts for simplified packaging, high spectral utilization due to a metallic, highly reflective and specular back surface reflector, and a practical method for scale‐up to full wafer devices. The n/p/n MIM TPV devices described in this work utilize a tunnel junction and a double heterostructure for improved performance. Lattice‐mismatched 0.6 eV, epitaxially grown InGaAs diodes form the power‐producing element. A power conversion efficiency of 20.6&percent; and a power density of 0.90 W/cm2with a silicon carbide radiator operating at 1058°C is achieved for a 4 cm2(die area) TPV cell operating at 26.7°C. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1539396

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

With the device performance of 0.6eV InGaAs monolithic interconnected modules (MIMs) reaching open circuit voltages of 400 mV/junction and achieving excellent quantum efficiency, the next step to improve performance focuses on controlling the parasitic optical absorption in these MIMs. With an integrated spectral control approach, the design of grid finger and interconnect metallization affects both the output power and the optical absorption of the MIM. The effect of metal coverage on the optical and electrical performance of MIMs processed in a multi‐wafer environment is presented. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1539397

出版商:AIP    

年代:1903

数据来源: AIP

摘要:

GaSb thermophotovoltaic (TPV) cells are the most suitable choice for modern TPV generators, both in terms of efficiency and simplicity of the diffusion technology used. Actually, TPV generators based on GaSb solar cells are the only ones available on the market. However, TPV cells with band gaps (Eg) lower than GaSb are expected to be advantageous for low‐temperature (< 1000°C) non‐wavelength‐selective TPV radiators because they provide more effective absorption of the blackbody infrared radiation. In this work, together with GaSb (Eg= 0.72 eV), semiconductors with a lower Eg‐ Ge (Eg= 0.66 eV), InGaSb (Eg= 0.60 eV), InGaAsSb (Eg= 0.55 eV) and InAsSbP (Eg= 0.39 eV) ‐ were studied for TPV cells. InGaAsSb cells seem to be the most promising candidate to replace GaSb cells in the low‐temperature TPV generators. © 2003 American Institute of Physics

ISSN:0094-243X    

DOI:10.1063/1.1539398

出版商:AIP    

年代:1903

数据来源: AIP