Side chain engineering of polymer acceptors for all-polymer solar cells with enhanced efficiency

Abstract

Side chain engineering of fused bithiophene imide oligomers yields a new series of random copolymers with tunable polymer chain packing and film morphology. When applied in all-polymer solar cells, an 8.32% efficiency is obtained.

A Terpolymer Acceptor Enabling All‐Polymer Solar Cells with a Broad Donor:Acceptor Composition Tolerance and Enhanced Stability

“…The all‐PSCs based on PBTI2(0HD)‐FT showed a J sc of 8.89 mA cm −2 , a fill factor (FF) of 47.23%, and a V oc of 1.02 V, yielding a PCE of 4.28%, which is comparable with the previous report. [ 59 ] As the f‐BTI2‐HD with a shorter 2‐HD side‐chain was incorporated into the parent polymer, a greatly enhanced PCE of 7.23% with a V oc of 1.04 V, a J sc of 12.54 mA cm −2 , and an FF of 55.45% was obtained for terpolymer PBTI2(30HD)‐FT‐based all‐PSCs without any solvent additives. However, with further increasing the f‐BTI2‐HD content, the PCEs dropped to 6.41% and 6.24% for PBTI2(50HD)‐FT‐ and PBTI2(70HD)‐FT‐based all‐PSCs, respectively, which are still much higher than that (4.28%) of the control device.…”

“…[ 59 ] These n‐type polymers were prepared according to Stille cross‐coupling polymerization of f‐BTI2‐DT, f‐BTI2‐HD, and FT monomers using various feed ratios between f‐BTI2‐DT and f‐BTI2‐HD having 2‐ DT and 2‐ HD side‐chains, respectively (Scheme S1, Supporting Information). [ 59,60 ] The polymers are designated as PBTI2( x HD)‐FT, where x (i.e., 30, 50, 70) represents the percentage of f‐BTI2‐HD relative to both f‐BTI2 units (f‐BTI2‐HD + f‐BTI2‐DT). The copolymer PBTI2(0HD)‐FT was also synthesized for comparison.…”

“…The synthetic and purification procedures for the random terpolymers with different side-chains are based on previous reports. [59] These n-type polymers were prepared according to Stille cross-coupling polymerization of f-BTI2-DT, f-BTI2-HD, and FT monomers using various feed ratios between f-BTI2-DT and f-BTI2-HD having 2-DT and 2-HD side-chains, respectively (Scheme S1, Supporting Information). [59,60] The polymers are designated as PBTI2(xHD)-FT, where x (i.e., 30,50,70) represents the percentage of f-BTI2-HD relative to both f-BTI2 units (f-BTI2-HD þ f-BTI2-DT).…”

“…[ 58 ] For example, we have previously reported that all‐PSCs based on f‐BTI2 terpolymer acceptors with distinct side chains of 2‐octyldodecyl (2‐OD) and 2‐decyltetradecyl (2‐DT) achieved an impressive PCE of ≈ 8.0%, suggesting that the side‐chain engineering of terpolymer acceptors is considerably significant for developing high‐performance all‐PSCs. [ 59 ] However, there are yet no analogous study on the effect of high D:A ratio on photovoltaic performance in terpolymer‐based all‐PSCs, while it is of great importance for further understanding this side‐chain engineering technique.…”

Acceptor–acceptor-type conjugated polymer semiconductors

“…For example, A8 and A9 were synthesized through the precursor to form an intramolecular imine bridge when triflu-oroacetic acid and anisole were used as catalysts and dichloromethane was used as a solvent [26]. Additionally, block copolymers (b2, b3, and c4) can be regarded as the combination of two SA-WA structure units and synthesized by Stille polymerization similar to polymerization of SA-WA-type polymers, in which three reactive substrates are added in proportions designed in advance [62,93,94].…”