High performance p-type molecular electron donors for OPV applications via alkylthiophene catenation chromophore extension

摘要

The synthesis of key 4-alkyl-substituted 5-(trimethylsilyl)thiophene-2-boronic acid pinacol esters >3 allowed a simplified alkylthiophene catenation process to access bis-, ter-, quater-, and quinquethiophene π-bridges for the synthesis of acceptor–π-bridge-donor– π-bridge-acceptor (A–π-D–π-A) electron donor molecules. Based on the known benzodithiophene-terthiophene-rhodanine (>BTR) material, the >BXR series of materials, >BMR (X = M, monothiophene), >BBR (X = B, bithiophene), known >BTR (X = T, terthiophene), >BQR (X = Q, quaterthiophene), and >BPR (X = P(penta), quinquethiophene) were synthesised to examine the influence of chromophore extension on the device performance and stability for OPV applications. The >BT >^x >R (x = 4, butyl, and x = 8, octyl) series of materials were synthesised by varying the oligothiophene π-bridge alkyl substituent to examine structure–property relationships in OPV device performance. The devices assembled using electron donors with an extended chromophore (>BQR and >BPR) are shown to be more thermally stable than the >BTR containing devices, with un-optimized efficiencies up to 9.0% PCE. >BQR has been incorporated as a secondary donor in ternary blend devices with >PTB7-Th resulting in high-performance OPV devices with up to 10.7% PCE.