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Venkatesan S, Ngo EC, Chen Q, et al. Benzothiadiazole-based polymer for single and double junction solar cells with high open circuit voltage. Nanoscale. 2014;6(12):7093-100doi: 10.1039/c4nr01040j.
Venkatesan, S., Ngo, E. C., Chen, Q., Dubey, A., Mohammad, L., Adhikari, N., Mitul, A. F., & Qiao, Q. (2014). Benzothiadiazole-based polymer for single and double junction solar cells with high open circuit voltage. Nanoscale, 6(12), 7093-100. https://doi.org/10.1039/c4nr01040j
Venkatesan, Swaminathan, et al. "Benzothiadiazole-based polymer for single and double junction solar cells with high open circuit voltage." Nanoscale vol. 6,12 (2014): 7093-100. doi: https://doi.org/10.1039/c4nr01040j
Venkatesan S, Ngo EC, Chen Q, Dubey A, Mohammad L, Adhikari N, Mitul AF, Qiao Q. Benzothiadiazole-based polymer for single and double junction solar cells with high open circuit voltage. Nanoscale. 2014 Jun 21;6(12):7093-100. doi: 10.1039/c4nr01040j. PMID: 24844939.
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Nanoscale. 2014 Jun 21;6(12):7093-100. doi: 10.1039/c4nr01040j.

Benzothiadiazole-based polymer for single and double junction solar cells with high open circuit voltage.

Nanoscale

Swaminathan Venkatesan, Evan C Ngo, Qiliang Chen, Ashish Dubey, Lal Mohammad, Nirmal Adhikari, Abu Farzan Mitul, Qiquan Qiao

Affiliations

  1. Center for Advanced Photovoltaics, Department of Electrical Engineering, South Dakota State University, Brookings, SD, USA. [email protected].

PMID: 24844939 DOI: 10.1039/c4nr01040j

Abstract

Single and double junction solar cells with high open circuit voltage were fabricated using poly{thiophene-2,5-diyl-alt-[5,6-bis(dodecyloxy)benzo[c][1,2,5]thiadiazole]-4,7-diyl} (PBT-T1) blended with fullerene derivatives in different weight ratios. The role of fullerene loading on structural and morphological changes was investigated using atomic force microscopy (AFM) and X-ray diffraction (XRD). The XRD and AFM measurements showed that a higher fullerene mixing ratio led to breaking of inter-chain packing and hence resulted in smaller disordered polymer domains. When the PBT-T1:PC60BM weight ratio was 1 : 1, the polymer retained its structural order; however, large aggregated domains formed, leading to poor device performance due to low fill factor and short circuit current density. When the ratio was increased to 1 : 2 and then 1 : 3, smaller amorphous domains were observed, which improved photovoltaic performance. The 1 : 2 blending ratio was optimal due to adequate charge transport pathways giving rise to moderate short circuit current density and fill factor. Adding 1,8-diiodooctane (DIO) additive into the 1 : 2 blend films further improved both the short circuit current density and fill factor, leading to an increased efficiency to 4.5% with PC60BM and 5.65% with PC70BM. These single junction solar cells exhibited a high open circuit voltage at ∼ 0.9 V. Photo-charge extraction by linearly increasing voltage (Photo-CELIV) measurements showed the highest charge carrier mobility in the 1 : 2 film among the three ratios, which was further enhanced by introducing the DIO. The Photo-CELIV measurements with varying delay times showed significantly higher extracted charge carrier density for cells processed with DIO. Tandem devices using P3HT:IC60BA as bottom cell and PBT-T1:PC60BM as top cell exhibited a high open circuit voltage of 1.62 V with 5.2% power conversion efficiency.

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