The impact of quantum dot concentration on the optical properties of QD/PMMA luminescent down-shifting films applied to CdTe photovoltaic devices

• Published in: Nano energy Vol. 4; pp. 1 - 6
• Main Authors: Hodgson, S.D., Brooks, W.S.M., Clayton, A.J., Kartopu, G., Barrioz, V., Irvine, S.J.C.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Ltd 01-03-2014; Elsevier
• Subjects: Applied sciences; CdTe; Chemistry; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemistry; Energy; Equipments, installations and applications; Exact sciences and technology; General and physical chemistry; Luminescent down-shifting; Natural energy; Photoelectric conversion; Photoelectrochemistry. Electrochemiluminescence; Photon management; Photovoltaic conversion; Photovoltaics; Quantum dots; Solar cells. Photoelectrochemical cells; Solar energy; Photon management; Quantum dots; CdTe; Luminescent down-shifting; Photovoltaics; Encapsulation; Quantum dot; Methyl methacrylate polymer; Concentration; Thin film; Photovoltaic cell; Semiconductor quantum dots; Optical properties; Performance; Photoconductivity; Nanostructured materials
• ISSN: 2211-2855
• DOI: 10.1016/j.nanoen.2013.12.004

Semiconductor quantum dots (QDs) have been encapsulated in poly(methyl, methacrylate) (PMMA) to prepare luminescent down-shifting films. The concentration of the QDs within each film has been varied, up to a maximum of 240µg/mm3 and the optical properties have been characterised in detail. The QD/PMMA films have been placed over thin-film CdS/CdTe photovoltaic devices and improvements to cell performance have been recorded via external quantum efficiency and current–voltage measurements. The best overall improvement to performance, compared to the uncoated device, was 1.7%. This was obtained with a QD density of 48µg/mm3, while the largest improvement to short-wavelength photocurrent was 30.30%, with a QD density of 192µg/mm3. To further explain these results laser beam induced current measurements were carried out using laser wavelengths of 405 and 658nm on individual cells with and without QD/PMMA films attached.
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•CdTe photovoltaics suffer from a filtering effect caused by the window layer.•Commercially available semiconductor quantum dots are encapsulated in a PMMA film with a range of concentrations.•The effect of QD concentration on the optical properties of the films has been characterised in detail.•LDS increases the performance, particularly the short wavelength photo-conversion, of a CdTe device.•Laser Beam Induced Current (LBIC) measurements of films show gains and losses and relates them back to QD concentrations.