TY - JOUR
T1 - Quinoxaline-Based Wide Band Gap Polymers for Efficient Nonfullerene Organic Solar Cells with Large Open-Circuit Voltages
AU - Yang, Jie
AU - Uddin, Mohammad Afsar
AU - Tang, Yumin
AU - Wang, Yulun
AU - Wang, Yang
AU - Su, Huimin
AU - Gao, Rutian
AU - Chen, Zhi Kuan
AU - Dai, Junfeng
AU - Woo, Han Young
AU - Guo, Xugang
N1 - Funding Information:
X.G. is grateful to the National Science Foundation of China (21774055), Shenzhen Peacock Plan Project (KQTD20140630110339343), Shenzhen Basic Research Fund (JCYJ20160530185244662), Guangdong Natural Science Foundation (2015A030313900), and South University of Science and Technology of China (FRG-SUSTC1501A-72). M.A.U. and H.Y.W. acknowledge the financial support from the NRF of Korea (2015R1D1A1A09056905, 20100020209) and Korea University Grant.
Publisher Copyright:
Copyright © 2018 American Chemical Society.
PY - 2018/7/11
Y1 - 2018/7/11
N2 - We present here a series of wide-band-gap (Eg: >1.8 eV) polymer donors by incorporating thiophene-flanked phenylene as an electron-donating unit and quinoxaline as an electron-Accepting co-unit to attain large open-circuit voltages (Vocs) and short-circuit currents (Jscs) in nonfullerene organic solar cells (OSCs). Fluorination was utilized to fine-Tailor the energetics of polymer frontier molecular orbitals (FMOs) by replacing a variable number of H atoms on the phenylene moiety with F. It was found that fluorination can effectively modulate the polymer backbone planarity through intramolecular noncovalent S···F and/or H···F interactions. Polymers (P2-P4) show an improved molecular packing with a favorable face-on orientation compared to their nonfluorinated analogue (P1), which is critical to charge carrier transport and collection. When mixed with IDIC, a nonfullerene acceptor, P3 with two F atoms, achieves a remarkable Voc of 1.00 V and a large Jsc of 15.99 mA/cm2, simultaneously, yielding a power-conversion efficiency (PCE) of 9.7%. Notably, the 1.00 V Voc is among the largest values in the IDIC-based OSCs, leading to a small energy loss (Eloss: 0.62 eV) while maintaining a large PCE. The P3:IDIC blend shows an efficient exciton dissociation through hole transfer even under a small energy offset of 0.16 eV. Further fluorination leads to the polymer P4 with increased chain-Twisting and mismatched FMO levels with IDIC, showing the lowest PCE of 2.93%. The results demonstrate that quinoxaline-based copolymers are promising donors for efficient OSCs and the fluorination needs to be fine-Adjusted to optimize the interchain packing and physicochemical properties of polymers. Additionally, the structure-property correlations from this work provide useful insights for developing wide-band-gap polymers with low-lying highest occupied molecular orbitals to minimize Eloss and maximize Voc in nonfullerene OSCs for efficient power conversion.
AB - We present here a series of wide-band-gap (Eg: >1.8 eV) polymer donors by incorporating thiophene-flanked phenylene as an electron-donating unit and quinoxaline as an electron-Accepting co-unit to attain large open-circuit voltages (Vocs) and short-circuit currents (Jscs) in nonfullerene organic solar cells (OSCs). Fluorination was utilized to fine-Tailor the energetics of polymer frontier molecular orbitals (FMOs) by replacing a variable number of H atoms on the phenylene moiety with F. It was found that fluorination can effectively modulate the polymer backbone planarity through intramolecular noncovalent S···F and/or H···F interactions. Polymers (P2-P4) show an improved molecular packing with a favorable face-on orientation compared to their nonfluorinated analogue (P1), which is critical to charge carrier transport and collection. When mixed with IDIC, a nonfullerene acceptor, P3 with two F atoms, achieves a remarkable Voc of 1.00 V and a large Jsc of 15.99 mA/cm2, simultaneously, yielding a power-conversion efficiency (PCE) of 9.7%. Notably, the 1.00 V Voc is among the largest values in the IDIC-based OSCs, leading to a small energy loss (Eloss: 0.62 eV) while maintaining a large PCE. The P3:IDIC blend shows an efficient exciton dissociation through hole transfer even under a small energy offset of 0.16 eV. Further fluorination leads to the polymer P4 with increased chain-Twisting and mismatched FMO levels with IDIC, showing the lowest PCE of 2.93%. The results demonstrate that quinoxaline-based copolymers are promising donors for efficient OSCs and the fluorination needs to be fine-Adjusted to optimize the interchain packing and physicochemical properties of polymers. Additionally, the structure-property correlations from this work provide useful insights for developing wide-band-gap polymers with low-lying highest occupied molecular orbitals to minimize Eloss and maximize Voc in nonfullerene OSCs for efficient power conversion.
KW - energy losses
KW - fluorination
KW - nonfullerene organic solar cells
KW - open-circuit voltages
KW - polymer semiconductors
UR - http://www.scopus.com/inward/record.url?scp=85048810124&partnerID=8YFLogxK
U2 - 10.1021/acsami.8b04432
DO - 10.1021/acsami.8b04432
M3 - Article
C2 - 29911382
AN - SCOPUS:85048810124
VL - 10
SP - 23235
EP - 23246
JO - ACS applied materials & interfaces
JF - ACS applied materials & interfaces
SN - 1944-8244
IS - 27
ER -