Browsing by Author "Cheng, Lung-Teng"

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Crystalline Engineering Toward Large-Scale High-Efficiency Printable Cu(In,Ga)Se-2 Thin Film Solar Cells on Flexible Substrate by Femtosecond Laser Annealing Process
(2017-04-26)
Chen, Shih-Chen
;
She, Nian-Zu
;
Wu, Kaung-Hsiung
;
Chen, Yu-Ze
;
Lin, Wei-Sheng
Ink-printing method emerges as a viable way for manufacturing large-scale flexible Cu(In,Ga)Se-2 (CIGS) thin film photovoltaic (TFPV) devices owing to its potential for the rapid process, mass production, and low-cost nonvacuum device fabrication. Here, we brought the femtosecond laser annealing (fs-LA) process into the ink-printing CIGS thin film preparation. The effects of fs-LA treatment on the structural and optoelectronic properties of the ink-printing CIGS thin films were systematically investigated. It was observed that, while the film surface morphology remained essentially unchanged under superheating, the quality of crystallinity was significantly enhanced after the fs-LA treatment. Moreover, a better stoichiometric composition was achieved with an optimized laser scanning rate of the laser beam, presumably due to the much reduced indium segregation phenomena, which is believed to be beneficial in decreasing the defect states of In-se, V-Se, and In-cu. Consequently, the shunt leakage current and recombination centers were enhancement in photovoltaic conversion efficiency. both greatly decreased, resulting in a near 20%
Highly Efficient Flexible Hybrid Nanocrystal-Cu(In,Ga)Se-2 (CIGS) Solar Cells
(2015-01-21)
Liao, Yu-Kuang
;
Brossard, Mael
;
Hsieh, Dan-Hua
;
Lin, Tzu-Neng
;
Charlton, Martin D. B.
A novel scheme for hybridizing inkjet-printed thin film Cu(In,Ga)Se-2 (CIGS) solar cells with self-assembled clusters of nanocrystal quantum dots (NQDs), which provides a 10.9% relative enhancement of the photon conversion efficiency (PCE), is demonstrated. A non-uniform layer of NQD aggregates is deposited between the transparent conductive oxide and a CdS/CIGS p-n junction using low cost pulsed-spray deposition. Hybridization significantly improves the external quantum efficiency of the hybrid devices in the absorption range of the NQDs and in the red to near-IR parts of the spectrum. The low wavelength response enhancement is found to be induced by luminescent down-shifting (LDS) from the NQD layer, while the increase at longer wavelengths is attributed to internal scattering from NQD aggregates. LDS is demonstrated using time-resolved spectroscopy, and the morphology of the NQD layer is investigated in fluorescence microscopy and cross-sectional transmission electron microscopy. The influence of the NQD dose on the PCE of the hybrid devices is investigated and an optimum value is obtained. The low costs and limited material consumptions associated with pulsed-spray deposition make these flexible hybrid devices promising candidates to help push thin-film photovoltaic technology towards grid parity.