A Dimethyldihydropyrene π-Switch for Light-Mediated Dynamic Control of Charge Transportation

Triarylamines (TAA) have low ionization potentials and are commonly used as donor units in optoelectronic materials. On the other hand, photochromic dimethyldihydropyrene (DHP) can switch between a highly conjugated DHP form and a less conjugated cyclophanediene (CPD) form. The reversible dynamic switching of the HOMO–LUMO energy gap and, consequently, the electrical conductance in an organic molecular material was realized by using a DHP π-switch flanked by TAA units. The aggregated structures of the closed form of the conjugated material were observed as regular cuboids under FESEM, whereas in the open form, the materials displayed irregular structures. Solid state I–V measurements showed that in the "ON" state of the switch, 55 times higher conductance was observed than in the corresponding "OFF" state. The solution state measurements showed that the "ON" state is 3.5 times more conducting than the "OFF" state. The reversibility of the conductance switching was observed in the solution without any significant degradation after 10 cycles.