3D Charge Transport Pathway in Organic Solar Cells via Incorporation of Discotic Liquid Crystal Columns

In this work, a discotic liquid crystal (DLC) 2,3,6,7,10,11-hexaacetoxytriphenylene (HATP) is used as the interlayer between poly(3,4-ethylene-dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) and the active layer to achieve 3D charge transportation for organic solar cells (OSCs). HATP exhibits a columnar structure with a dominantly edge-on orientation. For a (non-)fullerene OSC system based on face-on orientation, HATP columns are favorable for the expansion of edge-on and face-on crystallite in the active layer. According to the surface energy, surrounding the HATP columns are mainly acceptors. The significantly improved electron mobility indicates that it is easier for the electron to hop into HATP columns to transport, which represents the formation of the 3D pathway. This transport mode typically can enhance the intermolecular charge transport and effectively suppress the generation of triplet excitons and recombination. Thus, the short-circuit current density (J(SC)) is increased by 14% and 19% for fullerene and non-fullerene systems, respectively. The power conversion efficiency is improved for non-fullerene OSCs with different active layer thicknesses (>= 150 nm) and fullerene OSCs with an active layer thickness of 140 nm. Overall, this work demonstrates an approach to introduce HATP columns on a PEDOT:PSS layer that has great potential to form a 3D pathway for achieving high-performance (non-)fullerene OSCs.