The paper proposes an experimental approach to determine the external quantum efficiency of multijunction solar cells with pronounced optical coupling. A new technique based on the cascade mechanism ...of coupling has been elaborated to separate the influence of the induced luminescent flux from the external illumination and to establish the absolute values of photosensitivity without negative impact of optical interaction between subcells. The novelty of this work lies in the method extended to multijunction devices with N-number of subcells.
•Cascade optical coupling is a feature of multi-junction solar cells.•Optical coupling negatively impacts on quantum efficiency measurements.•Method describes how to avoid influence of optical coupling on experimental data.
Solar spectral irradiance blurring in the focal plane of the Fresnel lens arising from the chromatic aberration (CA) inherent to a lens was studied. The experimental complex for recording both ...irradiance distribution and spectral irradiance redistribution for the radiation concentrated by a small-sized energy concentrator based on a solar simulator with the possibility of modeling the spectral composition of light is presented. The methodology for scanning the irradiance spectral redistribution by a fiber spectrometer is described.
Presented are technical solutions on constructing optical systems for experimental simulating the sunlight parameters. Designs of two types of solar simulators are proposed. In the first one, the ...spectrum and the radiation angular divergence are simulated on the basis of a continuous light source, what corresponds to the principle "necessity and sufficiency" of simulated parameters of the light flux in investigating optical and power characteristics of small-size sunlight concentrators (Fresnel lenses). In the second type simulator, based on a pulsed radiation source, the emphasis has been placed on high-quality simulation of irradiance and spectrum for satisfying requirements in recording current-voltage characteristics of multijunction solar cells and in determining their efficiency.
In the present work processes of direct light coupling in the triple-junction solar cells between top GaInP (wide band gap) and bottom Ge (narrow band gap) subcells are considered, when parameters of ...intermediate optical medium (comprised of middle GaAs p-n junction layers) are changed. Conditions of luminescent coupling gain and blocking are studied in multijunction structures with selectively tuned built-in photonic structures such as Bragg reflectors. An ability to manage the efficiency of optical interaction between subcells is investigated.
In this paper, triple-junction solar cells of various middle junction thickness are studied. It is shown that in samples with thin layers, an optical coupling between the top and the bottom subcell ...is possible as well as a direct leakage of external radiation through the middle one. True values of the spectral dependences of the external quantum efficiency are calculated in accordance with the corrective method. The proposed method reveals some difference in the negative contribution of the luminescence and the positive signal results from the light penetration.
In the work, optical coupling arising in a multijunction solar cell under powerful laser radiation is investigated. To describe the cascade of interconnected luminescent processes in a structure with ...optical coupling, the photon-coupled characteristic is used. Investigation for two specimens with different effeciency of luminescent interaction was carried out.
The work is aimed at the study of multijunction solar cells with built-in Bragg reflectors. The possibility to use the photon structure for "locking" the secondary recombination radiation, which ...causes luminescent coupling between individual photoactive p-n junctions in a solar cell, is investigated. Temperature studies were carried out on the reflection spectra of a Bragg reflector, the electroluminescence spectrum of a middle wide bandgap subcell, and the spectra of the external quantum efficiency of a multijunction solar cell.
A procedure for estimating an optical leakage of incoming radiation through a wide-bandgap subcell in a GaInP/GaInAs/Ge multijunction solar cell to photoactive layers of narrow-bandgap ones is ...proposed. A sequence for experimental determination of currents induced in a Ge subcell owing to an optical leakage or via a luminescent coupling is described.
In the present work, an opportunity to block the negative influence of luminescent coupling between subcells in multijunction solar cells with help of built-in Bragg reflectors is investigated. ...Temperature modes, at which the blocking of optical interaction in the GaAs-Ge pair of subcells is possible, have been determined.
In the work, the link of registered relative and absolute current signals of different amplitude and shape in recording spectral characteristics of the sunlight PV converter external quantum ...efficiency is investigated, and the need to use absolute current in spectral response studies of multijunction solar cells with clearly pronounced luminescent coupling is established.
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