TY - JOUR
T1 - Benzodithiophene-Dithienylbenzothiadiazole Copolymers for Efficient Polymer Solar Cells
T2 - Side-Chain Effect on Photovoltaic Performance
AU - Huang, Lanqi
AU - Zhang, Guangjun
AU - Zhang, Kai
AU - Peng, Qiang
AU - Wong, Man Shing
N1 - Funding Information:
The work was supported by the Institute of Molecular Functional Materials, a grant from the University Grants Committee, Areas of Excellence Scheme (AoE/P-03/08), the NSFC (51573107, 91633301, and 21432005), and the Foundation of State Key Laboratory of Polymer Materials Engineering (sklpme2017-2-04).
Publisher copyright:
© 2018 American Chemical Society
PY - 2018/10/10
Y1 - 2018/10/10
N2 - A new series of low band gap D-A alternating polymers based on 4,5-bis((2-ethylhexyl)oxy)benzo[2,1-b:3,4-b′]dithiophene (BDT) and 5-fluoro-4,7-bis(4-alkylthien-2-yl)benzo[c][1,2,5]thiadiazole bearing different size of lateral alkyl substituents, namely, PfBB-n, n = 8, 10, 12, 14, and 16, was designed and synthesized for high-performance bulk heterojunction (BHJ) polymer solar cells (PSCs). PfBB-n-bearing linear alkyl side chains exhibited strong and controllable aggregation in both solution and solid states, which gives rise to a significant bathochromic shift of the absorption cut-off down to ∼780 nm in thin film. In addition, the strong and wide absorption (350-800 nm) of PfBB-n polymers can compensate for the relatively weak absorption of PC71BM, particularly in the 300-400 range nm to enhance light harvesting of such an active blend. BHJ solar cells based on PfBB-n:PC71BM blends as an active layer showed power conversion efficiency (PCE) in the range 7.8-9.7%. Because of the strong stacking interchain interactions, PfBB-12-based PSC exhibited aggregation-induced spectral broadening, superior structural order, higher exciton dissociation, higher and more balanced charge carrier mobilities, as well as reduced recombination losses. As a result, PfBB-12-based device afforded the best PCE of 9.7%, with the highest short-circuit current density (Jsc) of 16.6 mA cm-2 and open-circuit voltage (Voc) of 0.92 V among devices fabricated. These results demonstrate that the alkyl side chain of the polymer significantly affects the absorption, morphology, and electronic properties of the active blend of PfBB-n/PC71BM, which would provide an alternative useful tool to fine-tune the device performance. Our results also highlight that the electron-rich benzo[2,1-b:3,4-b′]dithiophene building block, BDT, is highly useful for the construction of low band gap D-A polymer for highly efficient PSCs.
AB - A new series of low band gap D-A alternating polymers based on 4,5-bis((2-ethylhexyl)oxy)benzo[2,1-b:3,4-b′]dithiophene (BDT) and 5-fluoro-4,7-bis(4-alkylthien-2-yl)benzo[c][1,2,5]thiadiazole bearing different size of lateral alkyl substituents, namely, PfBB-n, n = 8, 10, 12, 14, and 16, was designed and synthesized for high-performance bulk heterojunction (BHJ) polymer solar cells (PSCs). PfBB-n-bearing linear alkyl side chains exhibited strong and controllable aggregation in both solution and solid states, which gives rise to a significant bathochromic shift of the absorption cut-off down to ∼780 nm in thin film. In addition, the strong and wide absorption (350-800 nm) of PfBB-n polymers can compensate for the relatively weak absorption of PC71BM, particularly in the 300-400 range nm to enhance light harvesting of such an active blend. BHJ solar cells based on PfBB-n:PC71BM blends as an active layer showed power conversion efficiency (PCE) in the range 7.8-9.7%. Because of the strong stacking interchain interactions, PfBB-12-based PSC exhibited aggregation-induced spectral broadening, superior structural order, higher exciton dissociation, higher and more balanced charge carrier mobilities, as well as reduced recombination losses. As a result, PfBB-12-based device afforded the best PCE of 9.7%, with the highest short-circuit current density (Jsc) of 16.6 mA cm-2 and open-circuit voltage (Voc) of 0.92 V among devices fabricated. These results demonstrate that the alkyl side chain of the polymer significantly affects the absorption, morphology, and electronic properties of the active blend of PfBB-n/PC71BM, which would provide an alternative useful tool to fine-tune the device performance. Our results also highlight that the electron-rich benzo[2,1-b:3,4-b′]dithiophene building block, BDT, is highly useful for the construction of low band gap D-A polymer for highly efficient PSCs.
KW - aggregation
KW - low band gap
KW - organic solar cells
KW - polymer donor
KW - side-chain effect
UR - http://www.scopus.com/inward/record.url?scp=85054327409&partnerID=8YFLogxK
U2 - 10.1021/acsami.8b13274
DO - 10.1021/acsami.8b13274
M3 - Journal article
C2 - 30209951
AN - SCOPUS:85054327409
SN - 1944-8244
VL - 10
SP - 34355
EP - 34362
JO - ACS Applied Materials and Interfaces
JF - ACS Applied Materials and Interfaces
IS - 40
ER -
