Synthesis and Photovoltaic Properties of Poly(dithieno[3,2-b:2′,3′-d]germole) Derivatives

Abstract

A series of new dithieno[3,2-b:2′,3′-d]germole copolymers have been synthesized and characterized. The dithienogermole unit has been polymerized with different aromatic comonomers such as the benzothiadiazole (PGe1-C8 and PGe1-EH) and thieno[3,4-c]pyrrole-4,6-dione (PGe2). Suzuki and Stille coupling polymerizations under various conditions have been utilized. The polymers were then characterized by size-exclusion chromatography and thermal analyses (TGA, DSC), and their optical and electronic properties were investigated by UV–vis absorption spectroscopy and cyclic voltammetry. These low bandgap polymers (1.3–1.7 eV) have also been tested for photovoltaic applications; the best result was achieved with polymer PGe2, which shows a power conversion efficiency of 4.1%.

Influence of the Electron Deficient Co‐Monomer on the Optoelectronic Properties and Photovoltaic Performance of Dithienogermole‐based Co‐Polymers

“…We note in the case of PDTG-BT , low molecular weight polymers have shown signifi cantly lower photocurrents in blends with PC 70 BM . [ 14,15 ] We further note that during the preparation of this manuscript Ohshita and coworkers have reported a PDTG-PT with a M n of 6.2 kDa.…”

“…The molecular lower device effi ciency. [ 14,15 ] Moreover, co-polymerization of DTG with different electron withdrawing groups, [ 16,17 ] such as 5-octyl-4 H -thieno [3,4-c ]pyrrole-4,6(5 H )-dione ( TPD ) provide polymers with PCE of 7.4% [ 17 ] with a lower J sc of 13.0 mA cm −2 but with an increased V oc of 0.87 V as compared to PDTG-BT . [ 13 ] Interestingly, the performance of some DTG based-polymers in OPV devices has shown an increase in the PCE compared to that of the analogous carbon or silicon bridged alternatives.…”

Dielectric Effect on the Photovoltage Loss in Organic Photovoltaic Cells

“…The molecular structures of the materials used for this study are shown in Figure a. Three of these polymers, poly[[9‐(1‐octylnonyl)‐9H‐carbazole‐2,7‐diyl]‐2,5‐thiophenediyl‐2,1,3‐benzothiadiazole‐4,7‐diyl‐2,5‐thiophenediyl] (PCDTBT), poly (dithienogermole–thienopyrrolodione) (PDTG‐TPD), and poly (dithienosilole–thienopyrrolodione) (PDTS‐TPD), have been reported with V OC values larger than 0.85 V. Poly (dithienosilole‐isoindigo) [PDTS‐iI] and poly[[4,8‐bis[(2‐ethylhexyl)oxy]benzo[1,2‐b:4,5‐b']dithiophene‐2,6‐diyl][3‐fluoro‐2‐[(2‐ethylhexyl)carbonyl]thieno[3,4‐b]thiophenediyl]] (PTB7) have medium V OC values of about 0.75 V, whereas poly (dithienogermole‐benzothiadiazole) (PDTG‐BTD) and P3HT have smaller V OC s of about 0.6 V.…”

Intramolecular Energy Transfer in Dithienogermole Derivatives

“…Actually,a lkyl-substituted DTG polymers show similara bsorption spectra in solution regardless of the alkyl chains, that is, methyl, octyl, or 2-ethylhexyl. [18,21,25] However, it has been recently demonstrated that the electron-donating/accepting aryl substituents give sufficient perturbation to the electronic states of the DTG system. [34] Ottosson's group theoretically predicted that silole rings have certaina romaticityi nt he excited state depending on the substituents on the silicon atom, suggesting the electronic influence of the substituents in ah eteroles ystem with a group 14 element.…”