(325c) Interconnection of Liquid Crystal Domains By Polyethylene Oxide Networks for Long-Range Conducting Channels Towards Efficient and Thermally Stable Advanced Energy Devices

Development of efficient electrolyte combining fast charge transport and high stability remains huge challenge because these two characters are trade off in normal design. Ionic liquid crystals, combining dynamically ordered nanostructures and thermal stability, have shown potential as efficient electrolytes. Despite the thermal stability and improved performance at elevated temperatures, the efficiency of the liquid crystals based DSSCs still need to be further improved for practical applications. Liquid crystal electrolytes, without control of molecular orientation, only formed partially continuous channels at the border of polydomains in the electrolytes. The boundaries between the polydomains acted as structural defects trapping the charge transport at the interfaces of liquid crystal domains, which hindered the overall charge transport in the electrolytes. Macroscopic alignment of the liquid crystal molecules, via methods such as mechanical shearing or surface treatment, could effectively tune the polydomained assembly into monodomain state, which constructed uniformly aligned conducting channels to significantly improve the charge transport. However, improvement of charge transport in liquid crystals via macroscopic alignment could hardly be achieved in energy devices, considering the device fabrication and the electrode surface.

Herein, we exemplifies a novel and convenient approach to construct self-assembled long-range conducting channels for liquid crystal electrolytes in energy devices. A solid-state liquid crystal gel electrolyte was designed and prepared by introducing polyethylene oxide (PEO) networks into smectic electrolytes, and applied for an efficient and thermally stable dye-sensitized solar cell (DSSC). DSSCs have received worldwide attention in recent years due to their relatively high energy conversion efficiency, low production cost and easy fabrication. However, the DSSCs containing liquid electrolytes have not achieved the anticipated commercial potential owing to the stability and lifetime issues of the device, which is largely due to the volatilization and potential leakage of the solvents under outdoor variations.

In the prepared gel electrolyte, smectic assembly formed lamellar nanostructures for charge transport at intra-domains, while the PEO networks aggregated amorphously at the smectic domain interfaces, acting as bridges to interconnect the domains for promotion of the charge transport via segmental motion at inter-domains. The coordination of the smectic assembly and PEO aggregation greatly enhanced both the charge transport and the device stability.The resultant solid-state DSSC showed significantly improved and thermally stable photovoltaic performance towards practical applications, which exhibited a champion efficiency of 7.2%, as well as steady photovoltaic performance within a wide temperature range from 30 to 70 ^oC and stored after 5000 h. The approach, using PEO networks to interconnect smectic domains for improvement of charge transport and device stability for self-assembled long-range charge transport channels, have great potential towards efficient electrolytes in large-scale advanced energy conversion and storage devices.