Low band gap conjugated polymers combining siloxane-terminated side chains and alkyl side chains: side-chain engineering achieving a large active layer processing window for PCE > 10% in polymer solar cells

Abstract

Side-chain random copolymers show high 3-D hole transport and offer excellent active layer thickness tolerance.

The influence of siloxane side-chains on the photovoltaic performance of a conjugated polymer

“…This trend indicates that a lower degree of polymerization was achieved for polymers with higher siloxane content, but that these nevertheless show a higher tendency for aggregation in o-DCB at elevated temperature. The difference in degree of polymerization could therefore be related to premature aggregation in the polymerization mixture, thereby inhibiting the reaction, an effect previously observed by Liu et al, 27 indicating that polymer solubility during polymerization can have an effect on molecular weight obtained. This implies that polymers with a high siloxane content have a low intrinsic and overall solubility coupled with a low M p , whereas polymers with a low siloxane content have higher intrinsic and overall solubilities coupled with a high M p .…”

“…Also in solar cells siloxane containing polymers have been introduced to increase crystallinity of the electron donor, inuencing the morphology of the blend layers. [25][26][27][28] This has led to highly performance solar cells, with PCE of 11%, when siloxane side chains were combined with regular alkyl chains within the same polymer. 27 Interestingly, it was shown that the number average molecular weight (M n ) decreased with increasing siloxane content, as polymers with high siloxane content were less soluble and could not reach high M n 's before becoming insoluble.…”

“…[25][26][27][28] This has led to highly performance solar cells, with PCE of 11%, when siloxane side chains were combined with regular alkyl chains within the same polymer. 27 Interestingly, it was shown that the number average molecular weight (M n ) decreased with increasing siloxane content, as polymers with high siloxane content were less soluble and could not reach high M n 's before becoming insoluble. 27 In this work, siloxane side chains are employed on diketopyrrolopyrrole (DPP) polymers, a class of conjugated polymers that has shown high promise in solar cell applications.…”

“…27 Interestingly, it was shown that the number average molecular weight (M n ) decreased with increasing siloxane content, as polymers with high siloxane content were less soluble and could not reach high M n 's before becoming insoluble. 27 In this work, siloxane side chains are employed on diketopyrrolopyrrole (DPP) polymers, a class of conjugated polymers that has shown high promise in solar cell applications. 29 In particular, siloxane side chains were introduced in varying concentrations on poly[{2,5-bis(2-hexyldecyl)-2,3,5,6-tetrahydro-3,6-dioxopyrrolo [3,4-c]pyrrole-1,4-diyl}-alt-{[2,2 0 -(1,4-phenylene) bisthiophene]-5,5 -diyl}] (PDPPTPT), 30 in this way nely tuning the solubility.…”

Morphology Driven by Molecular Structure of Thiazole‐Based Polymers for Use in Field‐Effect Transistors and Solar Cells

“…[5][6][7][8] Significant research effortsh ave been devoted to developing donor-acceptor (D-A)-typec opolymers with ab road light absorption spectrum and ah igh charge-carrier mobility. [5,7,9,10] Benzo [1,2-b:4,5-b']dithiophene (BDT) and dithieno[2,3-d:2',3'-d']benzo [1,2-b:4,5-b']dithiophene( DTBDT) derivatives have been widely used as electron-donating units in polymers emiconductors. [7,8,[10][11][12] Composed of fused aromatic and planar core units,t hese derivativesd isplay high charge-charierm obility.…”