Flash technique for GaAs concentrator solar cell measurement

Fanetti, E.

doi:10.1049/el:19810327

Cited by 6 publications

(2 citation statements)

References 4 publications

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“…Also included in Figure are dashed contours showing the required concentration for a 50% efficient module with electrically series‐connected subcells and a 90% optical efficiency (series‐connected cell efficiency not shown on this 2D plot). The color scale corresponds to the efficiency of the photovoltaic cell under ideal illumination, analog to the flash test efficiency used to evaluate current monolithic MJSCs . As the color scale indicates, both 3% and 5% ERE cells with four or more subcells can achieve 50% cell efficiency even at one sun concentration, in contrast to the current record four‐junction cell efficiency of 46% at 508 suns.…”

Section: Resultsmentioning

confidence: 99%

Design of photovoltaics for modules with 50% efficiency

Warmann

Flowers

Lloyd

et al. 2017

Energy Science & Engineering

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A wide variety of photovoltaic cell technologies have shown dramatic performance improvements over the past decade, yet the prospect of a practical module capable of 50% efficiency remains remote. Experimentally achieved singlecell devices have achieved a record efficiency of 28.8% [1], which is close to the theoretical limit of 33.8% for such devices [2]. However, the single-cell limit is far below the fundamental efficiency limit for solar energy conversion of 74.0% for global illumination and 92.8% for direct [2] because a single pn junction can only efficiently convert photons with energy close to the value of its energy bandgap. The best single junction cell will lose more than 40% of the energy in the incident light to transmission of subbandgap photons and thermalization of carriers with photon energy in excess of the bandgap [3]. Spectrum splitting, which divides the solar spectrum into spectral bands of different energy and directs the bands onto multiple subcells with bandgap values matched to the energy of their photon allocation, is a necessary feature of any photovoltaic design capable of achieving >33.8% efficiency. The use of multiple subcells to increase conversion efficiency is well known. In these designs, the subcells are grown monolithically in a stacked configuration and are electrically in series. The incident spectrum is divided among the subcells by sequential absorption, with the top subcells absorbing and converting high energy photons

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Section: Resultsmentioning

confidence: 99%

Design of photovoltaics for modules with 50% efficiency

Warmann

Flowers

Lloyd

et al. 2017

Energy Science & Engineering

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“…The single-flash concentrated light I-V characterization strategy can be subdivided into two different techniques: one of them is based on a flash discharge characterized by a flat plateau irradiance profile (i.e. the flash light intensity is approximately constant during several milliseconds) throughout which different points of the I-V curve are measured [Fanetti, 1981]; the other technique consists of tracing 6.2. Concentrated light characterization systems the I-V curve during a relatively short time lapse of non-constant (although not very varying) irradiance and then extrapolating all data points to a constant irradiance level by means of a calibrated reference cell and the corresponding analytical model that also takes into account the spectrum non-uniformities.…”

Section: Multi-flash Vs Single Flash Systemsmentioning

confidence: 99%

Research on intermediate band solar cells and development of experimental techniques for their characterization under concentrated illumination

Fontes¹

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This work is a contribution to the research and development of the intermediate band solar cell (IBSC), a high efficiency photovoltaic concept that features the advantages of both low and high bandgap solar cells. The resemblance with a low bandgap solar cell comes from the fact that the IBSC hosts an electronic energy band -the intermediate band (IB)-within the semiconductor bandgap. This IB allows the collection of sub-bandgap energy photons by means of two-step photon absorption processes, from the valence band (VB) to the IB and from there to the conduction band (CB). The exploitation of these low energy photons implies a more efficient use of the solar spectrum. The resemblance of the IBSC with a high bandgap solar cell is related to the preservation of the voltage: the open-circuit voltage (V OC ) of an IBSC is not limited by any of the sub-bandgaps (involving the IB), but only by the fundamental bandgap (defined from the VB to the CB).Nevertheless, the presence of the IB allows new paths for electronic recombination and the performance of the IBSC is degraded at 1 sun operation conditions. A theoretical argument is presented regarding the need for the use of concentrated illumination in order to circumvent the degradation of the voltage derived from the increase in the recombination. This theory is supported by the experimental verification carried out with our novel characterization technique consisting of the acquisition of photogenerated current (I L )-V OC pairs under low temperature and concentrated light. Besides, at this stage of the IBSC research, several new IB materials are being engineered and our novel characterization tool can be very useful to provide feedback on their capability to perform as real IBSCs, verifying or disregarding the fulfillment of the "voltage preservation" principle.An analytical model has also been developed to assess the potential of quantum-dot (QD)-IBSCs. It is based on the calculation of band alignment of III-V alloyed heterojunctions, the estimation of the confined energy levels in a QD and the calculation of the detailed balance efficiency. Several potentially useful QD materials have been identified, such as InAs/Al x Ga 1-x As, InAs/Ga x In 1-x P, InAs 1-y N y /AlAs x Sb 1-x or InAs 1-z N z /Al x [Ga y In 1-y ] 1-x P.Finally, a model for the analysis of the series resistance of a concentrator solar cell has also been developed to design and fabricate IBSCs adapted to 1,000 suns. i ResumenEste trabajo contribuye a la investigación y al desarrollo de la célula solar de banda intermedia (IBSC), un concepto fotovoltaico de alta eficiencia que aúna las ventajas de una célula solar de bajo y de alto gap. La IBSC se parece a una célula solar de bajo gap (o banda prohibida) en que la IBSC alberga una banda de energía -la banda intermedia (IB)en el seno de la banda prohibida. Esta IB permite colectar fotones de energía inferior a la banda prohibida por medio de procesos de absorción de fotones en dos pasos, de la banda de valencia (VB) a la IB y de allí a la banda de condu...

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