9,9-Dialkylfluorene-alt-benzothiadiazole-based bolaamphiphiles with the formation of complex self-assembled liquid-crystalline phases of a cubic A15 network and Colsqu/p4gm at the triangle–square transition†

Two novel series of bolaamphiphiles containing two 9,9-dialkylfluorenes interconnected by a benzothiadiazole core via a single bond (series Fn) or thiophene links (series TFn), with polar glycerol groups at both ends, have been designed and synthesized to study the complex transitional liquid-crystalline phases between triangular and square honeycombs. Indeed, besides triangular and square honeycomb phases, the A15 type cubic network of rod-bundle phases was found in series Fn, while the honeycomb structure with the Col_squ/p4gm phase, which combines triangular and square tiles in a ratio of 2 : 1, was found in TFn series. Additionally, the application of Fn and TFn as bright yellow and red light-emitting liquid crystal displays (LE-LCDs), white light-emitting diodes (WLEDs) and dopants in PEDOT:PSS/n-Si heterojunction solar cells to improve the photoelectric conversion efficiency (PCE) of the device was successfully realized, and the resulting device offered high PCE values of up to 13.44% and 13.97%, respectively.