A low band gap co-polymer of dithienogermole and 2,1,3-benzothiadiazole by Suzuki polycondensation and its application in transistor and photovoltaic cells

Abstract

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

“…[ 13 ] At the same period of time, other groups have also reported the synthesis of lower molecular weight PDTG-BT that exhibits somewhat The PCE of PDTG-PT is further improved to 6.6% when the device architecture is modifi ed from normal to inverted. Therefore, PDTG-PT is an ideal candidate for application in tandem solar cells confi guration due to its high effi ciency at very low band gaps ( E g opt = 1.32 eV).…”

“…[20][21][22][23] Here, we report the synthesis, characterization and device properties of all three co-polymers ( PDTG-BTz , PDTG-DFBT , PDTG-PT ), and compare their performance to previously reported BT co-polymer. [ 13 ] We observe signifi cant differences in optoelectronic properties and device performance and relate these to the nature of the acceptor co-monomer. [ 19 ] 4,7-dibromo-2-octyl-2 Hbenzo[ d ] [1,2,3]triazole, [ 24 ] 4,7-Dibromo- [1,2,5] thiadiazolo [3,4-c ] pyridine, [ 21,25 ] and 4,7-dibromo-5,6-difl uorobenzo[ c ][1,2,5] thiadiazole, [ 26 ] were all synthesized according to the previously reported literature.…”

“…[ 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. [ 18,19 ] This effect has been attributed to the increase in carbon-germanium bond length compared to the carbon-carbon or carbon-silicon bonds in CPDT and DTS respectively.…”

“…[1][2][3][4][5] Computational density functional theory (DFT) calculations on donor-acceptor co-polymers have typically shown that the HOMO is delocalized over the conjugated backbone whilst the LUMO is more strongly localized on the acceptor co-monomer. [6][7][8] Therefore, tuning of either the electron rich or electron defi cient unit is an effective method to engineer the band gap and energetic levels of the resulting co-polymers.Electron [9][10][11][12][13] Previously, we have reported the synthesis of high molecular weight PDTG-BT and demonstrated PCE of 4.5% in OPV devices with promisingly high short circuit currents ( J sc ) of 18.6 mA cm −2 after annealing. [ 13 ] At the same period of time, other groups have also reported the synthesis of lower molecular weight PDTG-BT that exhibits somewhat The PCE of PDTG-PT is further improved to 6.6% when the device architecture is modifi ed from normal to inverted.…”

“…Electron [9][10][11][12][13] Previously, we have reported the synthesis of high molecular weight PDTG-BT and demonstrated PCE of 4.5% in OPV devices with promisingly high short circuit currents ( J sc ) of 18.6 mA cm −2 after annealing. [ 13 ] At the same period of time, other groups have also reported the synthesis of lower molecular weight PDTG-BT that exhibits somewhat The PCE of PDTG-PT is further improved to 6.6% when the device architecture is modifi ed from normal to inverted.…”