TY - JOUR
T1 - Using pyridal[2,1,3]thiadiazole as an acceptor unit in a low band-gap copolymer for photovoltaic applications
AU - Ibraikulov, Olzhas A.
AU - Bechara, Rony
AU - Chavez, Patricia
AU - Bulut, Ibrahim
AU - Tastanbekov, Dias
AU - Leclerc, Nicolas
AU - Hebraud, Anne
AU - Heinrich, Benoît
AU - Berson, Solenn
AU - Lemaitre, Noëlla
AU - Chochos, Christos L.
AU - Lévêque, Patrick
AU - Heiser, Thomas
N1 - Funding Information:
We thank the Centre National de la Recherche Scientifique (CNRS), Total E&P Kazakhstan and Rhin-Solar project supported by the European Fund for Regional Development (FEDER) in the framework of the Programme INTERREG IV Upper Rhine for financial support. We want to thank as well Pohang Accelerator Laboratory (PAL) for giving us the opportunity to perform the GIWAXS measurements, MEST and POSTECH for supporting these experiments, Dr. Tae Joo Shin for adjustments and help, and other people from 9A U-SAXS beamline for assistance. This research was supported by Leading Foreign Research Institute Recruitment Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning ( NRF-2010-00453 ).
PY - 2015/8/1
Y1 - 2015/8/1
N2 - Abstract In this report, we explore the optoelectronic properties of a low band-gap copolymer based on the alternation of electron rich (thiophene and thienothiophene units) and electron deficient units (pyridal[2,1,3]thiadiazole (Py)). Initial density functional theory calculations point out the interest of using the Py unit to optimize the polymer frontier orbital energy levels. A high molecular weight (Mn = 49 kg/mol) solution-processable copolymer, based on Py, thiophene and thienothiophene units, has been synthesized successfully. From cyclic-voltammetry and UV-visible absorption measurements a relatively deep HOMO level (-5.1 eV) and an optical band-gap (1.48 eV) have been estimated. Charge transport both in horizontal and vertical directions were extracted from field-effect transistors and space charge limited current diodes, respectively, and led to a relatively high in-plane hole mobility in pure polymer films (0.7 × 10-2 cm2 V-1 s-1). GIWAXS results showed almost identical in-plane lamellar morphologies, with similar average size and orientation of the polymer crystalline domains in both, pure polymer films and polymer:fullerene blends. Also, the gate-voltage dependence of the field-effect mobility revealed that the energy disorder in the polymer domains was not altered by the introduction of fullerenes. The nevertheless significantly higher out-of-plane hole mobility in blends, in comparison to pure polymer films, was attributed to the minor amorphous polymer phase, presumably localized close to the donor/acceptor interface, whose signature was observed by UV-vis absorption. Promising photovoltaic performances could be achieved in a standard device configuration. The corresponding power conversion efficiency of 4.5% is above the value achieved previously with a comparable polymer using benzo [2,1,3]thiadiazole instead of Py as acceptor unit.
AB - Abstract In this report, we explore the optoelectronic properties of a low band-gap copolymer based on the alternation of electron rich (thiophene and thienothiophene units) and electron deficient units (pyridal[2,1,3]thiadiazole (Py)). Initial density functional theory calculations point out the interest of using the Py unit to optimize the polymer frontier orbital energy levels. A high molecular weight (Mn = 49 kg/mol) solution-processable copolymer, based on Py, thiophene and thienothiophene units, has been synthesized successfully. From cyclic-voltammetry and UV-visible absorption measurements a relatively deep HOMO level (-5.1 eV) and an optical band-gap (1.48 eV) have been estimated. Charge transport both in horizontal and vertical directions were extracted from field-effect transistors and space charge limited current diodes, respectively, and led to a relatively high in-plane hole mobility in pure polymer films (0.7 × 10-2 cm2 V-1 s-1). GIWAXS results showed almost identical in-plane lamellar morphologies, with similar average size and orientation of the polymer crystalline domains in both, pure polymer films and polymer:fullerene blends. Also, the gate-voltage dependence of the field-effect mobility revealed that the energy disorder in the polymer domains was not altered by the introduction of fullerenes. The nevertheless significantly higher out-of-plane hole mobility in blends, in comparison to pure polymer films, was attributed to the minor amorphous polymer phase, presumably localized close to the donor/acceptor interface, whose signature was observed by UV-vis absorption. Promising photovoltaic performances could be achieved in a standard device configuration. The corresponding power conversion efficiency of 4.5% is above the value achieved previously with a comparable polymer using benzo [2,1,3]thiadiazole instead of Py as acceptor unit.
KW - Charge transport
KW - Energy disorder
KW - Field-effect mobility
KW - Morphology
KW - Polymer solar cells
KW - Space-charge-limited current
UR - http://www.scopus.com/inward/record.url?scp=84928656476&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=84928656476&partnerID=8YFLogxK
U2 - 10.1016/j.orgel.2015.04.018
DO - 10.1016/j.orgel.2015.04.018
M3 - Article
AN - SCOPUS:84928656476
VL - 23
SP - 171
EP - 178
JO - Organic Electronics
JF - Organic Electronics
SN - 1566-1199
M1 - 3055
ER -