Poly(thieno[3,4-b]furan), a New Low Band Gap Polymer: Experiment and Theory

Abstract

A new optically transparent, near-infrared-absorbing low energy gap conjugated polymer, poly (thieno[3,4-b]furan) (PT34bF), with promising attributes for photovoltaics is reported herein. PT34bF was prepared electrochemically, and upon redox cycling, doping was found to be anion dominant. The energy gap of the polymer was found to be 1.04 eV as calculated from the low-energy edge of the absorption spectrum of the neutral polymer at -0.6 V and 1.03 eV for the chemically neutralized polymer using hydrazine. The polymer is pale blue in the neutral form and a more transparent pale blue in the oxidized conducting state with photopic transmittances of 62% and 72% (ITO glass substrate not subtracted), indicating the possibility of application as a transparent conductor or an ion-storage layer for electronic devices. Density functional theory (DFT) calculations using B3PW91 hybrid functional have been carried out for possible connections between the three open R-positions. In addition to optimizing geometry, band structure properties such as band (energy) gaps, band widths, and effective masses were calculated for each connection. Calculations show that 4-6 connectivity is the most probable and dominant structure for the polymer resulting from T34bF, and the calculated energy gap of 1.01 eV for polymerization via this connection corresponds well with the experimentally observed value of 1.04 eV.

Developments of furan and benzodifuran semiconductors for organic photovoltaics

“…Sotzing and coworkers prepared this low band gap homopolymer by performing electrochemical polymerization on an inert electrode. 96 This product showed low band gap of 1.04 eV and stable redox behavior. In the past ve years, one of the most important developments in furan containing p-conjugated materials is the application in BHJ solar cells.…”

Band edge modulated conjugated polymers for oxidation prevention

“…The HOMO energy level of the polymers was calculated by normalizing the onset of oxidation peaks with respect to the potential of ferrocene/ferrocenium internal redox couple. 51,52 The LUMO energy levels were estimated by adding the optical bandgap to that of the HOMO energy levels estimated by cyclic voltammetry. 52 The band edges thus calculated for the four polymers are schematically shown in Fig.…”

“…51,52 The LUMO energy levels were estimated by adding the optical bandgap to that of the HOMO energy levels estimated by cyclic voltammetry. 52 The band edges thus calculated for the four polymers are schematically shown in Fig. 3.…”

Synthesis and Properties of a Chiroptically Active Oligomer from 3,4-Ethylenedioxythiophene and (–)-Myrtenal

“…Many kinds of conjugated polymers have been widely studied for applications, such as transparent conductors, light-emitting diodes, thin film transistors, and photovoltaic devices [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ]. Low-bandgap conjugated polymer is of interest because of its sensitivity in optical and electrical impulsions for external stimuli [ 10 , 11 , 12 , 13 , 14 ].…”