Browsing by Author "Kekuda, Dhananjaya"

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Dibenzo[f,h]thieno[3,4-b] quinoxaline-fullerene heterojunction bilayer solar cells with complementary spectrum coverage
(2010-10-01)
Kekuda, Dhananjaya
;
Huang, Jen-Shien
;
Velusamy, Marappan
;
Lin, Jiann T.
;
Chu, Chih-Wei
In the present article, potential of a bilayer organic solar cell has been investigated. We utilize newly synthesized small molecules, namely dibenzo[f,h]thieno[3,4-b]quinoxaline as electron donors for solar cells in heterojunction bilayer configuration. These small molecules with a narrow absorption band in the range 400-450 nm provide a complementary spectrum for the fullerene C(70), thereby leading to an overall power conversion efficiency of 2.6 +/- 0.2% under 100 mW/cm(2) incident radiation. Thermal annealing seems to impact the charge separation at the donor-acceptor interface, which eventually affects device performance. This work demonstrates that carefully optimized bilayer devices are comparable to the bulk heterojunction counterparts. (C) 2010 Elsevier B.V. All rights reserved.
Modulation of Donor-Acceptor Interface through Thermal Treatment for Efficient Bilayer Organic Solar Cells
(2010-02-18)
Kekuda, Dhananjaya
;
Huang, Jen-Hsien
;
Ho, Kuo-Chuan
;
Chu, Chih-Wei
;
光電工程學系
In this article, we demonstrate the effect of donor-acceptor (D-A) interface on the performance of bilayer organic solar cells. Solution processing was used to develop liquid crystal poly(9,9'-dioctylfluorene-co-bithiophene) (F8T2) polymer films and variable morphology of the films was achieved by varying the annealing temperature. The morphology of the annealed active layers signature a well-aligned nanodomain feature with an interdegitated structure at 200 degrees C. The devices with bilayer configuration, ITO/PEDOT:PSS/F8T2/C(70)/Al, have yielded a power conversion efficiency (PCE) of 3.4(+/- 0.2)% under 1 sun incident radiation. We attribute the high PCE to the increased D-A junction interface and balanced charge transport between electron/hole transport layers.
The effect of solvent induced crystallinity of polymer layer on poly(3-hexylthiophene)/C(70) bilayer solar cells
(2011-02-01)
Kekuda, Dhananjaya
;
Lin, Hao-Shing
;
Wu, Meng Chyi
;
Huang, Jen-Shein
;
Ho, Kuo-Chuan
A bilayer polymer solar cell is demonstrated with the device configuration ITO/PEDOT:PSS/poly(3-hexylthiophene)/C(70)/Al. In this article, we highlight the importance of polymer surface morphology, its crystallinity and mobility on device output parameters. The solvent used for polymer processing plays a major role in deciding these parameters and it was observed that high boiling point solvents are desirable for achieving large surface roughness of the polymer layer, which in turn provide more interface area in the bilayer device structure. Due to the increased interface area for exciton dissociation, these bilayer devices resulted in a maximum power conversion efficiency of 3.65% under one sun radiation. (C) 2010 Elsevier B.V. All rights reserved.
The effect of solvent induced crystallinity of polymer layer on poly(3-hexylthiophene)/C-70 bilayer solar cells
(2011-02-01)
Kekuda, Dhananjaya
;
Lin, Hao-Shing
;
Wu, Meng Chyi
;
Huang, Jen-Shein
;
Ho, Kuo-Chuan
A bilayer polymer solar cell is demonstrated with the device configuration ITO/PEDOT:PSS/poly(3-hexylthiophene)/C-70/Al. In this article, we highlight the importance of polymer surface morphology, its crystallinity and mobility on device output parameters. The solvent used for polymer processing plays a major role in deciding these parameters and it was observed that high boiling point solvents are desirable for achieving large surface roughness of the polymer layer, which in turn provide more interface area in the bilayer device structure. Due to the increased interface area for exciton dissociation, these bilayer devices resulted in a maximum power conversion efficiency of 3.65% under one sun radiation. (C) 2010 Elsevier B.V. All rights reserved.