Singlet fission (SF) has been proven to be an effective strategy to overcome the Shockley–Queisser limit of photovoltaics. However, the materials suitable for SF are relatively rare due to the strict requirements for the occurrence of this process. In the present study, we report the first preparation of two heteroatoms (O and S)‐doped polycyclic aromatic hydrocarbons (PAHs) molecules with (β, β) connected furan/thiophene ring. The optical and physiochemical properties of both compounds are investigated by a variety of spectroscopies, including UV–vis absorption, photoluminescence and cyclic voltammetry. In addition, their ultrafast excited state dynamics are studied by femtosecond transient absorption. Experimental data showed that the singlet fission efficiency was improved by 2 times when replacing oxygen with sulfur atom, which could provide some guidelines in designing singlet fission materials with better efficiency.

Development of new n‐type one‐dimensional (1D) self‐assembly nanostructure and a clear understanding of the relationship between molecular structure and self‐assembly behavior are important prerequisites for further designing and optimizing organic optoelectronic nanodevice. In this article, a series of n‐type organic semiconductor materials based on pyrene imide were successfully synthesized through [4+2] cycloaddition reactions and their preliminary optical and electrochemical properties were studied. The simulated HOMO‐LUMO bandgaps via DFT tallied with the experimental data well. The self‐assembly of these materials showed needle or fiber‐like morphologies, indicating that different conjugation degree or alkyl group had significant influence on their self‐assembly behaviors. Furthermore, the single‐crystal packing for these molecules were analyzed and it was found out that the changes of conjugated backbone and functional group would affect certain crystal lattice parameter significantly, such as the intermolecular packing distance and crystal size etc, which would further result in different self‐assembly morphology.