Browsing by Author "Ostapov, I. E."

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Novel regular D-A-conjugated polymers based on 2,6-bis(6-fluoro-2-hexyl-2H-benzotriazol-4-yl)-4,4-bis(2-ethylhexyl)-4H-silolo[3,2-b:4,5-b\']dithiophene derivatives: Synthesis, optoelectronic, and electrochemical properties
(2016-09)
Keshtov, M. L.
;
Kuklin, S. A.
;
Ostapov, I. E.
;
Chen, Fang-Chung
;
Khokhlov, A. R.
Regioregular (P1) and random (P2) polymers were prepared by the reaction of equimolar amounts of dibromides M2 or M3 with bis(stannyl) monomer M1. The regioregularity of the conjugated chain in P1 was shown to affect considerably its optical properties. The HOMO/LUMO values and electrochemical band gap for polymers P1 or P2 found by cyclic voltammetry are-5.40/-3.40,-5.31/-3.33, and 2.00/1.96 eV, respectively. The LUMO levels for P1 and P2 are located higher than for PC71BM (-4.3 eV) by 0.84 and 0.97 eV, respectively. The low-lying HOMO levels of P1 and P2 are favorable for the high value of open-circuit voltage and make these polymers attractable candidates for polymer solar cells.
Synthesis and characterization of two new benzothiadiazole- and fused bithiophene based low band-gap D-A copolymers: Application as donor bulk heterojunction polymer solar cells
(2015-05-18)
Keshtov, M. L.
;
Sharma, G. D.
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Kuklin, S. A.
;
Ostapov, I. E.
;
Godovsky, D. Yu.
Two new narrow bandgap D-A conjugated copolymers P1 and P2 containing different fused thiophene donor unit and same benzothiadiazole acceptor unit were synthesized by Stille cross-coupling polymerization, and characterized by H-1 NMR, elemental analysis and GPC, TGA, DSC. Cyclic voltammetry measurement showed that the HOMO energy level both copolymers is deep lying (-5.10 and -5.35 eV for P1 and P2, respectively) which show that copolymers has good stability in the air and assured a higher open circuit voltage when it photovoltaic application. These copolymer were used as donor along with PC71BM and the BHJ polymer solar cells based on P1:PC71BM and P2:PC71BM processed with chloroform (CF) solvent showed over all PCE of 4.54% and 4.36%, respectively. Additionally, the PCE was improved up to 5.62% and 5.24% for P1:PC71BM and P2:PC71BM active layer processed with DIO (4 v%)/CF solvent. The enhancement in the PCE has been attributed to improved nanoscale morphology and crystalline nature of active layer as well as charge transport in the device with the addition of DIO, due to the higher boiling point of DIO causing slow evaporation rate during the film formation. (C) 2015 Elsevier Ltd. All rights reserved.