Abstract
A phenanthrodithiophene (PDT)-difluorobenzoxadiazole (DFBO) copolymer, P-PDT-DFBO, was synthesized and characterized. Replacing a thiadiazole with an oxadiazole ring gives the synthesized polymer a highest occupied molecular orbital (HOMO) about 0.1 V lower, and lowest unoccupied molecular orbital energy levels lower than those of its benzothiadiazole (BT) counterpart, due to the more electron-deficient oxadiazole. Furthermore, since oxadiazole has a larger dipole moment than BT, P-PDT-DFBO exhibits greater aggregation strength than previously reported for P-PDT-DFBT. The low-lying HOMO level of P-PDT-DFBO gave about 0.1 V higher open-circuit voltage (Voc), yielding over 0.9 V in a fabricated solar cell. From grazing incidence wide-angle X-ray diffraction analysis, P-PDT-DFBO formed a favorable face-on orientation in both neat and blended films, indicating that the incorporation of an oxadiazole moiety can enhance Voc without any orientation change in the solid state. However, a P-PDT-DFBO-based cell exhibited significantly lower Jsc and FF, and thus less power conversion efficiency, not >4.43%, due to its lower hole mobility than P-PDT-DFBT. One possible reason for poor performance may be the low crystallinity of P-PDT-DFBO in blended film. This may be caused by its strong aggregation tendency, leading to fast crystallization into a semiamorphous structure or to interference with the construction of long-range ordered structure.
| Original language | English |
|---|---|
| Pages (from-to) | 2646-2655 |
| Number of pages | 10 |
| Journal | Journal of Polymer Science, Part A: Polymer Chemistry |
| Volume | 56 |
| Issue number | 23 |
| DOIs | |
| Publication status | Published - Dec 1 2018 |
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Keywords
- Benzoxadiazole
- Energy conversion
- molecular ordering
- open-circuit voltage
- organic photovoltaics
- Phenanthrodithiophene
- polymers
- semiconductors
ASJC Scopus subject areas
- Polymers and Plastics
- Organic Chemistry
- Materials Chemistry
Cite this
Development of a phenanthrodithiophene-difluorobenzoxadiazole copolymer exhibiting high open-circuit voltage in organic solar cells. / Mori, Hiroki; Takahashi, Ryosuke; Nishihara, Yasushi.
In: Journal of Polymer Science, Part A: Polymer Chemistry, Vol. 56, No. 23, 01.12.2018, p. 2646-2655.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Development of a phenanthrodithiophene-difluorobenzoxadiazole copolymer exhibiting high open-circuit voltage in organic solar cells
AU - Mori, Hiroki
AU - Takahashi, Ryosuke
AU - Nishihara, Yasushi
PY - 2018/12/1
Y1 - 2018/12/1
N2 - A phenanthrodithiophene (PDT)-difluorobenzoxadiazole (DFBO) copolymer, P-PDT-DFBO, was synthesized and characterized. Replacing a thiadiazole with an oxadiazole ring gives the synthesized polymer a highest occupied molecular orbital (HOMO) about 0.1 V lower, and lowest unoccupied molecular orbital energy levels lower than those of its benzothiadiazole (BT) counterpart, due to the more electron-deficient oxadiazole. Furthermore, since oxadiazole has a larger dipole moment than BT, P-PDT-DFBO exhibits greater aggregation strength than previously reported for P-PDT-DFBT. The low-lying HOMO level of P-PDT-DFBO gave about 0.1 V higher open-circuit voltage (Voc), yielding over 0.9 V in a fabricated solar cell. From grazing incidence wide-angle X-ray diffraction analysis, P-PDT-DFBO formed a favorable face-on orientation in both neat and blended films, indicating that the incorporation of an oxadiazole moiety can enhance Voc without any orientation change in the solid state. However, a P-PDT-DFBO-based cell exhibited significantly lower Jsc and FF, and thus less power conversion efficiency, not >4.43%, due to its lower hole mobility than P-PDT-DFBT. One possible reason for poor performance may be the low crystallinity of P-PDT-DFBO in blended film. This may be caused by its strong aggregation tendency, leading to fast crystallization into a semiamorphous structure or to interference with the construction of long-range ordered structure.
AB - A phenanthrodithiophene (PDT)-difluorobenzoxadiazole (DFBO) copolymer, P-PDT-DFBO, was synthesized and characterized. Replacing a thiadiazole with an oxadiazole ring gives the synthesized polymer a highest occupied molecular orbital (HOMO) about 0.1 V lower, and lowest unoccupied molecular orbital energy levels lower than those of its benzothiadiazole (BT) counterpart, due to the more electron-deficient oxadiazole. Furthermore, since oxadiazole has a larger dipole moment than BT, P-PDT-DFBO exhibits greater aggregation strength than previously reported for P-PDT-DFBT. The low-lying HOMO level of P-PDT-DFBO gave about 0.1 V higher open-circuit voltage (Voc), yielding over 0.9 V in a fabricated solar cell. From grazing incidence wide-angle X-ray diffraction analysis, P-PDT-DFBO formed a favorable face-on orientation in both neat and blended films, indicating that the incorporation of an oxadiazole moiety can enhance Voc without any orientation change in the solid state. However, a P-PDT-DFBO-based cell exhibited significantly lower Jsc and FF, and thus less power conversion efficiency, not >4.43%, due to its lower hole mobility than P-PDT-DFBT. One possible reason for poor performance may be the low crystallinity of P-PDT-DFBO in blended film. This may be caused by its strong aggregation tendency, leading to fast crystallization into a semiamorphous structure or to interference with the construction of long-range ordered structure.
KW - Benzoxadiazole
KW - Energy conversion
KW - molecular ordering
KW - open-circuit voltage
KW - organic photovoltaics
KW - Phenanthrodithiophene
KW - polymers
KW - semiconductors
UR - http://www.scopus.com/inward/record.url?scp=85055710644&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85055710644&partnerID=8YFLogxK
U2 - 10.1002/pola.29248
DO - 10.1002/pola.29248
M3 - Article
VL - 56
SP - 2646
EP - 2655
JO - Journal of Polymer Science, Part A: Polymer Chemistry
JF - Journal of Polymer Science, Part A: Polymer Chemistry
SN - 0887-624X
IS - 23
ER -