Browsing by Author "Yan, He"

Now showing 1 - 2 of 2

Selenophene-Incorporated Quaterchalcogenophene-Based Donor-Acceptor Copolymers To Achieve Efficient Solar Cells with J(sc) Exceeding 20 mA/cm(2)
(2017-12-12)
Cao, Fong-Yi
;
Tseng, Cheng-Chun
;
Lin, Fang-Yu
;
Chen, Yuzhong
;
Yan, He
Three selenophene-incorporated quaterchalcogenophene-based donoracceptor copolymers PFBT2Th2Se, PFBT2Se2Th, and PFBT4Se are designed and synthesized. To systematically fine-tune the molecular properties and investigate the chalcogen effect, PFBT2Th2Se and PFBT2Se2Th hybridize two thiophenes and two selenophenes as the donor with different isomeric main-chain placement while thiophene-free PFBT4Se uses quaterselenophene as the donor. On account of the selenophenes advantageous features such as higher quinoidal population and higher molecular polarizability, the three polymers show good light-harvesting ability, strong intermolecular interactions, high crystallinity, and high charge mobilities. Bulk-heterojunction solar cells incorporating these selenophene-containing polymers have exhibited promising photovoltaic performance with impressive current densities over 20 mA/cm(2). The device with the PFBT2Se2Th:PC71BM blend showed a PCE of 9.02% with a J(sc) of 21.02 mA/cm(2). In addition, the device using quaterselenophene-based PFBT4Se:PC71BM blend exhibited a PCE of 8.92% with a superior J(sc) of 22.63 mA/cm(2) which represents one of the highest current densities from polymer:fullerene-based solar cells reported in the literature.
Synthesis and side-chain isomeric effect of 4,9-/5,10-dialkylated-beta-angular-shaped naphthodithiophenes-based donor-acceptor copolymers for polymer solar cells and field-effect transistors
(2017-04-21)
Chiou, De-Yang
;
Cao, Fong-Yi
;
Hsu, Jhih-Yang
;
Tsai, Che-En
;
Lai, Yu-Ying
A systematic methodology is developed to construct the angular-shaped beta-form naphthodithiophene (beta-aNDT) core with regiospecific substitution of two alkyl groups at its 4,9-or 5,10-positions via the base-induced double 6 pi-cyclization of dithienyldieneyne precursors, leading to the two isomeric 4,9-beta-aNDT and 5,10-beta-aNDT monomers. It is found that a more curved geometry of the beta-aNDT units intrinsically increases the solubility and thus the solution-processability of the resultant polymers. Therefore, beta-aNDT units are ideal for polymerization with an acceptor-containing monomer without the need for any solubilizing aliphatic side chains, which are considered the insulating portion that jeopardizes charge transport. Based on this consideration, the 4,9- and 5,10-dialkylated beta-aNDT monomers are polymerized with the non-alkylated DTFBT acceptor to afford two P4,9-beta NDTDTFBT and P5,10-beta NDTDTFBT copolymers for head-to-head comparison of the 4,9-inner/5,10-outer isomeric alkylation effect. It is found that 4,9-beta aNDT adopts a twisted conjugated structure due to the intramolecular steric repulsion between the inner branched side chains and the beta-hydrogens on the thiophene rings. The slightly twisted 4,9-beta-aNDT moiety allows P4,9-beta NDTDTFBT to have higher solubility upon polymerization and thus a higher molecular weight, which eventually induces a higher ordered packing structure in the thin film compared to P5,10-beta NDTDTFBT. As a result, P4,9-beta NDTDTFBT exhibits a higher OFET mobility of 0.18 cm(2) V-1 s(-1), and the P4,9-beta NDTDTFBT: PC71BM-based solar cell device also achieves a higher PCE of 7.23%, which is even better than the corresponding P4,9-alpha NDTDTFBT-based device.