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Adv Mater. 2018 Mar;30(9). doi: 10.1002/adma.201706124. Epub 2018 Jan 15.

Fine-Tuning of Molecular Packing and Energy Level through Methyl Substitution Enabling Excellent Small Molecule Acceptors for Nonfullerene Polymer Solar Cells with Efficiency up to 12.54.

Author information

1
Hubei Key Lab on Organic and Polymeric Optoelectronic Materials, Department of Chemistry, Wuhan University, Wuhan, 430072, P. R. China.
2
Shenzhen Key Laboratory of Polymer Science and Technology, College of Materials Science and Engineering, Shenzhen University, Shenzhen, 518060, China.
3
CAS Research/Education Center for Excellence in Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, China.
4
Heeger Beijing Research and Development Center, School of Chemistry and Environment, Beihang University, Beijing, 100191, P. R. China.
5
Department of Physics and Astronomy and Collaborative Innovation Center of IFSA (CICIFSA), Shanghai Jiaotong University, Shanghai, 200240, P. R. China.

Abstract

A novel small molecule acceptor MeIC with a methylated end-capping group is developed. Compared to unmethylated counterparts (ITCPTC), MeIC exhibits a higher lowest unoccupied molecular orbital (LUMO) level value, tighter molecular packing, better crystallites quality, and stronger absorption in the range of 520-740 nm. The MeIC-based polymer solar cells (PSCs) with J71 as donor, achieve high power conversion efficiency (PCE), up to 12.54% with a short-circuit current (JSC ) of 18.41 mA cm-2 , significantly higher than that of the device based on J71:ITCPTC (11.63% with a JSC of 17.52 mA cm-2 ). The higher JSC of the PSC based on J71:MeIC can be attributed to more balanced μhe , higher charge dissociation and charge collection efficiency, better molecular packing, and more proper phase separation features as indicated by grazing incident X-ray diffraction and resonant soft X-ray scattering results. It is worth mentioning that the as-cast PSCs based on MeIC also yield a high PCE of 11.26%, which is among the highest value for the as-cast nonfullerene PSCs so far. Such a small modification that leads to so significant an improvement of the photovoltaic performance is a quite exciting finding, shining a light on the molecular design of the nonfullerene acceptors.

KEYWORDS:

molecular packing; polymer solar cells; power conversion efficiencies; small molecular acceptors

PMID:
29334160
DOI:
10.1002/adma.201706124

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