Alkoxy-Functionalized Thienyl-Vinylene Polymers for Field-Effect Transistors and All-Polymer Solar Cells

• Published in: Advanced functional materials Vol. 24; no. 19; pp. 2782 - 2793
• Main Authors: Huang, Hui, Zhou, Nanjia, Ortiz, Rocio Ponce, Chen, Zhihua, Loser, Stephen, Zhang, Shiming, Guo, Xugang, Casado, Juan, López Navarrete, J. Teodomiro, Yu, Xinge, Facchetti, Antonio, Marks, Tobin J.
• Format: Journal Article
• Language: English
• Published: Blackwell Publishing Ltd 01-05-2014
• Subjects: all-polymer solar cells; conjugated polymers; Construction; Copolymerization; Nondestructive testing; O···S interaction; Photovoltaic cells; Polymers; Semiconductor devices; Solar cells; Thin film transistors
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201303219

π‐conjugated polymers based on the electron‐neutral alkoxy‐functionalized thienyl‐vinylene (TVTOEt) building‐block co‐polymerized, with either BDT (benzodithiophene) or T2 (dithiophene) donor blocks, or NDI (naphthalenediimide) as an acceptor block, are synthesized and characterized. The effect of BDT and NDI substituents (alkyl vs alkoxy or linear vs branched) on the polymer performance in organic thin film transistors (OTFTs) and all‐polymer organic photovoltaic (OPV) cells is reported. Co‐monomer selection and backbone functionalization substantially modifies the polymer MO energies, thin film morphology, and charge transport properties, as indicated by electrochemistry, optical spectroscopy, X‐ray diffraction, AFM, DFT calculations, and TFT response. When polymer P7 is used as an OPV acceptor with PTB7 as a donor, the corresponding blend yields TFTs with ambipolar mobilities of μe = 5.1 × 10−3 cm2 V–1 s–1 and μh = 3.9 × 10−3 cm2 V–1 s–1 in ambient, among the highest mobilities reported to date for all‐polymer bulk heterojunction TFTs, and all‐polymer solar cells with a power conversion efficiency (PCE) of 1.70%, the highest reported PCE to date for an NDI‐polymer acceptor system. The stable transport characteristics in ambient and promising solar cell performance make NDI‐type materials promising acceptors for all‐polymer solar cell applications.
Three classes of p‐ and n‐type conjugated polymers with different functional groups are designed and synthesized with electron neutral thienyl‐vinylene (TVTOEt) and electron rich or electron deficient building blocks. The different functional groups influence the polymer electronic energy levels, thin film morphologies, and charge transfer properties. The all‐polymer photovoltaic devices using the n‐type copolymer as the acceptor material exhibit good efficiency.