Traditional Si solar cells have a narrow active absorption cross section among the short wavelength range (200-400 nm). The down-shifting process can efficiently improve the spectral response of Si solar cells by converting shorter wavelengths (i.e., ultraviolet, UV) to longer wavelengths (i.e., the visible range). Here, ZnSe quantum dots (QDs), prepared by an aqueous solution method and employed as a luminescent down-shifting layer, were spin coated onto the upper surface of manufactured Si solar cells. Measurements under standard test conditions (AM1.5, 100 mW/cm 2 ) show that the efficiency of the ZnSe QDs-Si hybrid solar cell is increased from 11.48% to12%. The improvement of the ZnSe QDs-Si hybrid solar cell is ascribed to the efficient down-shifting process of ZnSe QDs, which enhances spectra response in the UV region for Si solar cells. The mechanism of this optical coupling and efficiency enhancement is investigated in detail. These results support the case that low-cost ZnSe QDs can be employed as efficient downshifting material on large-area solar cells.PACS Nos.: 81.07Ta, 77.84Bw, 88.40hj. Résumé : Les cellules solaires Si traditionnelles ont une section efficace d'absorption faible dans le domaine des ondes courtes (200-400 nm). Un mécanisme de décalage vers le bas (downshifting) peut améliorer l'efficacité des cellules solaires Si en convertissant les courtes longueurs d'onde (ultraviolet, UV) vers les longueurs d'onde du visible. Nous employons ici des points quantiques (QD) deZnSe, préparés en solution aqueuse, comme couche de convertisseur vers le bas et les appliquons par enduction centrifuge sur la surface de la cellule solaire Si manufacturée. Des mesures faites sous des conditions standardisées (AM1.5, 100 mW/cm 2 ) montrent que l'efficacité de la cellule solaire hybride ZnSe QD-Si voit son efficacité passer de 11.48% à 12%. Nous attribuons l'amélioration du cas hybride ZnSe QD-Si à une conversion efficace par les QD de ZnSe, qui augmente la réponse spectrale de la cellule Si dans l'UV. Nous étudions ici en détail le mécanisme de ce couplage optique et l'amélioration qu'il apporte. Ces résultats supportent l'utilisation des QD ZnSe peu chers comme convertisseurs efficaces pour les cellules solaires. [Traduit par Rédaction]

The stability and photoluminescence (PL) emission intensity of quantum dots (QDs) are particularly interesting for various bioapplications. In this paper, monodisperse CdTe/CdS core–shell QDs were synthesized in aqueous phase. The size of CdTe core and the thickness of CdS shell played important roles in the properties of CdTe/CdS QDs. Transmission electron microscopy (TEM) images show that the average diameters of CdTe/CdS core–shell QDs increased to ∼5 nm compared with that of CdTe core QDs (∼3.6 nm). X-ray diffraction patterns show that the CdTe/CdS core–shell QDs possess cubic zinc blende structure. After the overgrowth of CdS shell on CdTe core, a widely tunable PL emission wavelength (485–720 nm) of the core–shell QDs can be obtained, which covers nearly the full visible spectrum. The PL intensity of the CdTe/CdS core–shell QDs shows two-fold increase compared with that of the CdTe core QDs. PL results show that the photostability of the samples is enhanced through the growth of CdS on the CdTe QDs.

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