The temperature variation of the electron diffusion length and the internal quantum efficiency in GaAs electroluminescent diodes

A generalisation of Planck's law for the spontaneous emission from light emitting diodes with direct band gaps allows a calculation of the absolute spectral emission intensity to be performed when the applied voltage, temperature, and absorption coefficient of the light emitting region are known. For given values of these parameters the emission intensity is independent of the diode current and the quantum efficiency of the recombination process.GaAs LED spectra calculated on this basis are compared with measurements at 82 K and at 296 K, and are found to agree quite well. Differences are attributed to the uncertain knowledge of the absorption coefficient of the diode material.

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“…A formalism as described above has been used to extract values of the diffusion length Le from relative emission data [5]. …”

Section: The Integration Of Equation (8a) For the Distribution In (5bmentioning

confidence: 99%

'Hermite' states in the quantum interaction of vortices

2005

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“…The emitted light is dependent on the quasi-Fermi level (qFl) splitting, the depth profile of which will reflect the collection issues 8 . Therefore, under different external condition (illumination and applied voltage), the depth of emission will be modified, leading to a luminescence spectral variation 9,10 . The depth emission can modify the monitored spectra due to, for example, re-absorption on the light path to the surface or slight depth variation of the material absorptivity.…”

Section: Introductionmentioning

confidence: 99%

Investigation of carrier collection in multi-quantum well solar cells by luminescence spectra analysis

et al. 2015

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Multi-Quantum well solar cells (MQWSC) have been shown to present several advantages, among which are low dark currents and tunable bandgaps. They are especially suited for implementation in multi-junction cells, and are highly promising for absorbers in Hot Carrier Solar Cells (HCSC). Such applications require high concentration ratio, which arises the issue of collection efficiency. Whereas it is usually considered that collection in MQW is very close to unity at one sun, it has been shown to not be the case under high concentration at the maximum power point. We propose in this work to take advantage of the luminescence spectral variation to investigate the depth collection efficiency. In order to validate the model, a series of strain compensated InGaAs/GaAsP MQW solar cells with intentional variation of the MQW doping concentration are grown. This has the effect of switching the space charge region position and width as well as the electric field intensity. Recording the luminescence spectra at various illumination intensities and applied voltages, we show that the in-depth quasi-Fermi level splitting and thus collection properties can be probed. Other measurements (EQE, luminescence intensity variation) are shown to be consistent with these results. Regarding their use as HCSC, the luminescence of MQW solar cells has been mainly used so far for investigating the quasi-Fermi level splitting and the temperature. Our results improve our understanding by adding information on carrier transport.

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