Browsing by Author "Konstantinov, I. O."

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New iridium-containing conjugated polymers for polymer solar cell applications
(2018-11-07)
Keshtov, M. L.
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Kuklin, S. A.
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Konstantinov, I. O.
;
Chen, Fang-Chung
;
Xie, Zhi-yuan
A series of novel donor-acceptor (D-A) copolymers P1-P5 with iridium-complexed moieties in their side chains have been synthesized on the basis of a new iridium-containing monomer. The results obtained show that P1-P5 have good thermal stability (317-347 degrees C) for photovoltaic applications. These copolymers absorb visible light in a broad spectral range up to 680 nm. The optical bandgaps of P1-P5 are in the range of 1.96-2.08 eV, respectively. The HOMO and LUMO energy levels of the polymers P1-P5 estimated from cyclic voltammetry measurements indicate that these copolymers are suitable as electron donors along with PC71BM as an electron acceptor for bulk heterojunction polymer solar cells. BHJ polymer solar cells were developed based on blend compositions (P1-P5):PC71BM. The values of J(sc), V-oc, and FF are in the range of 0.95-4.44 mA cm(-2), 0.67-0.69 V and 34.6-56.8%, and the power conversion efficiencies (PCE) are in the range of 0.22-1.74%, respectively, the highest value of 1.74% being for P3. Increase of the photovoltaic parameters was achieved with increasing iridium complex percentage in the polymers due to involvement of triplet effects. The improvement in the efficiency of the triplet-forming polymers P2 and P3 in comparison with P1 appears to be due to the formation of triplet excitons in comparison with singlet excitons in the polymer P1 which does not contain heavy metals. With further increase in the content of iridium complex fragments in the polymers, for example, up to 3 mol% for polymer P4, the efficiency falls to 1.23% and further decreased to 0.22% for P5.
Polymer solar cells based low bandgap A1-D-A2-D terpolymer based on fluorinated thiadiazoloquinoxaline and benzothiadiazole acceptors with energy loss less than 0.5 eV
(2017-07-01)
Keshtov, M. L.
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Kuklin, S. A.
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Khokhlov, A. R.
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Osipov, S. N.
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Radychev, N. A.
We synthesized an ultra low bandgap terpolymer denoted as P containing fluorinated-fluorene attached thiadiazoloquinoxaline and benzothiadiazole acceptors and thiophene as donor in its backbone and investigated its optical and electrochemical properties. This terpolymer is used for as donor along with PC71BM as electron acceptor in solution processed polymer solar cells (PSCs). The P showed a shows strong absorption band from 650 nm to 1100 nm with an optical bandgap of 1.12 eV and highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of -5.25 eV and -3.87 eV, respectively. After the optimization of P to PC71BM weight ratio, the optimized weight ratio 1: 2 in chlorobenzene (CB) solution, the PSC showed overall power conversion efficiency of 4.10% (J(sc) of 10.96 mA/cm(2), V-oc of 0.68 V and FF of 0.55). After the solvent additive (3 v% DIO) followed by subsequent thermal annealing (SA-TA) the PCE has been increased up to 7.54% with Jsc of 16.12 mA/cm(2), Voc of 0.65 V and FF of 0.72. The increase in the PCE is related with the enhancement in the both Jsc and FF, attributed optimized nanoscale morphology of the active layer for both efficient exciton dissociation and charge transport towards the electrodes and balanced charge transport in the device, induced by the TSA treatment of the active layer. This is the highest PCE of PSCs with an energy loss about 0.47 eV with the low bandgap of 1.12 eV. (C) 2017 Elsevier B.V. All rights reserved.