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Research Papers

Effect of Crystallinity on the Performance of P3HT/PC70BM/n-Dodecylthiol Polymer Solar Cells

[+] Author and Article Information
Nidal Abu-Zahra

Materials Science and Engineering Department,
University of Wisconsin-Milwaukee,
Milwaukee, WI 53211
e-mail: nidal@uwm.edu

Mahmoud Algazzar

Materials Science and Engineering Department,
University of Wisconsin-Milwaukee,
Milwaukee, WI 53211
e-mail: algazzar@uwm.edu

Contributed by the Solar Energy Division of ASME for publication in the JOURNAL OF SOLAR ENERGY ENGINEERING. Manuscript received June 2, 2013; final manuscript received November 11, 2013; published online December 19, 2013. Assoc. Editor: Santiago Silvestre.

J. Sol. Energy Eng 136(2), 021023 (Dec 19, 2013) (7 pages) Paper No: SOL-13-1155; doi: 10.1115/1.4026100 History: Received June 02, 2013; Revised November 11, 2013

In this research, n-dodecylthiol was added to P3HT/PC70BM polymer solar cells (PSCs) to improve the crystallinity of P3HT and enhance the phase separation of P3HT/PC70BM. Crystallinity of P3HT:PC70BM doped with 0–5% by volume of n-dodecylthiol was measured using X-ray diffraction (XRD) and differential scanning calorimetry (DSC) techniques. Both methods showed improvement in crystallinity, which resulted in improving the power conversion efficiency (PCE) of polymer solar cells by 33%. In addition, annealing at 150 °C for 30 min showed further improvement in crystallinity with n-dodecylthiol concentration up to 2%. The highest power conversion efficiency of 3.21% was achieved with polymer crystallites size L of 11.2 nm, after annealing at 150 °C for 30 min under a vacuum atmosphere. The smaller crystallite size suggests a shorter path of the charge carriers between P3HT backbones, which could be beneficial to getting a higher short circuit current in the devices made with the additive. Kinetics study of P3HT:PC70BM crystallinity using Avrami model showed a faster crystallization rate (1/t0.5) at higher temperatures.

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Figures

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Fig. 1

Schematic diagram of the synthesized polymer solar cell

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Fig. 2

XRD spectra for P3HT: PC70BM: (0–5%) n-dodecylthiol: (a) before annealing, (b) after annealing at 150 °C for 10 min, (c) after annealing at 150 °C for 20 min, and (d) after annealing at 150 °C for 30 min

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Fig. 3

Effect of % n-dodecylthiol on crystallite size (L)

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Fig. 4

DSC heat flow of P3HT: PC70BM: (0–5%) n-dodecylthiol (a) before and (b) after annealing

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Fig. 5

Percent crystallinity for P3HT:PC70BM:(0–5%) n-dodecylthiol before and after annealing calculated from DSC results

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Fig. 6

Area under XRD peaks at various annealing temperatures

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Fig. 7

Avrami log equation for the samples prepared at various annealing temperatures

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Fig. 8

Short circuit current and open circuit voltage of P3HT:PC70BM with 0%-5% n-dodecylthiol content under AM 1.5 G illumination after annealing

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Fig. 9

PCE of Glass/ITO/PEDOT:PSS/P3HT:PC70BM: n-dodecylthiol/Al before and after annealing

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