Singlet fission induced giant optical limiting responses of pentacene derivatives

Most organic molecules exhibit photo-induced bleaching under intense laser irradiation, while fewer materials show reversed saturable absorption, i.e. optical limiting properties. Here, we report that pentacene derivatives exhibit a giant nonlinear optical response at 532 nm. Upon investigation by the Z-scan technique, the pentacene derivatives demonstrated strong reverse saturable absorption and self-focusing effects using 532 nmpulsed lasers on a broad timescale from picosecond to nanosecond, with excellent output in solvents and polymer film matrices. Phase object (PO)-pump-probe and Z-scan measurements reveal that the superior optical limiting behaviors can be attributed to an excited state absorption mechanism associated with large absorption cross sections. We obtained a new benchmark of optical limiting onset of 2 mJ cm(-2) with a concentrated solution, stemming from triplet state absorption due to the singlet fission process. This novel singlet fission induced nonlinear optical mechanism opens a new venue for the future design of organic optical limiting materials.