High‐Efficiency As‐Cast Organic Solar Cells Based on Acceptors with Steric Hindrance Induced Planar Terminal Group

Abstract

A series of alkyl, alkoxyl, and alkylthio substituted A–π–D–π–A type nonfullerene acceptors (NFAs) IDTCN‐C, IDTCN‐O, and IDTCN‐S are designed and synthesized. The introduction of a lateral side chain at the outer position of the π bridge unit can endow the terminal moiety with a confined planar conformation due to the steric hindrance. Thus, compared with nonsubstituted NFA (IDTT2F), these acceptors tend to form favorable face‐on orientation and exhibit strong crystallinity as verified with grazing‐incidence wide‐angle X‐ray scattering measurement. Moreover, the variation of side chain can significantly change the lowest unoccupied molecular orbital (LUMO) energy level of acceptors. As state‐of‐the‐art NFAs, a power conversion efficiency of 13.28% (Voc = 0.91 V, Jsc = 19.96 mA cm−2, and FF = 73.2%) is obtained for the as‐cast devices based on IDTCN‐O, which is among the highest value reported in literature. The excellent photovoltaic performance for IDTCN‐O can be attributed to its slightly up‐shifted LUMO level and more balanced charge transport. This research demonstrates side chain engineering is an effective way to achieve high efficiency organic solar cells.

A Review of Grazing Incidence Small‐ and Wide‐Angle X‐Ray Scattering Techniques for Exploring the Film Morphology of Organic Solar Cells

“…Bo and coworkers reported that replacement of the alkyl chain with alkyloxy or alkylthio chains on π‐spacer of small acceptors has enhanced the crystallinity. [ 142 ] Recently, Bazan and coworkers also reported that replacement of the alkyl chain with alkyloxy chains on π‐spacer of small acceptors has significantly enhanced the crystallinity ( Figure ). [ 143 ] In this study, change was much prominent.…”

Isomerization Strategy of Nonfullerene Small‐Molecule Acceptors for Organic Solar Cells

“…Devices based on PBDB-T:IDT-ToFIC exhibited a higher PCE of 11.09% than its counterpart using PBDB-T:IDT-TiFIC (9.46%). In addition, the same group synthesized another pair of isomeric IDT-core based acceptors (IDTCN-O [124] and IDTOT2F [125] ), which differ in the alkoxy chains substitution cites (the IDT ladder core for DTCN-O Representative AFM height images of g) J61:m-ITIC and h) J61:ITIC blend films and corresponding AFM phase images of i) J61:m-ITIC and j) J61:ITIC blend films. Adapted with permission.…”

“…Devices based on PBDB‐T:IDT‐ToFIC exhibited a higher PCE of 11.09% than its counterpart using PBDB‐T:IDT‐TiFIC (9.46%). In addition, the same group synthesized another pair of isomeric IDT‐core based acceptors (IDTCN‐O [ 124 ] and IDTOT2F [ 125 ] ), which differ in the alkoxy chains substitution cites (the IDT ladder core for DTCN‐O and the thiophene π bridge for IDTOT2F). IDTCN‐O exhibits larger optical band gap and higher LUMO level than IDTOT2F.…”

Tetrabromination versus Tetrachlorination: A Molecular Terminal Engineering of Nonfluorinated Acceptors to Control Aggregation for Highly Efficient Polymer Solar Cells with Increased Voc and Higher Jsc Simultaneously

“…[ 13–23 ] Therefore, many such typed NF‐SMAs have been synthesized and become the mainstream materials for the development of high‐efficiency PSCs. [ 24–36 ] Recently, the power conversion efficiencies (PCEs) of NF‐SMAs‐based PSCs have been sharply increased over 16% in single‐junction binary and ternary devices, indicating their great potentials for further practical application. [ 37–57 ] NF‐SMAs, such as ITIC and Y6, typically comprise an electron‐rich fused core, side chain group, and electron‐deficient terminal groups, and all of which can be modified by introducing functional groups or atoms to better understand the structure–property relationship and improve the device performance of ITIC or Y6 series‐based PSCs.…”