Circularly Polarized Light Enhancement by Helical Polysilane Aggregates Suspension in Organic Optofluids

Abstract

Circularly polarized (CP) light may play key roles in the migration and delocalization of photoexcited energy in optically active macroscopic aggregates of chiral chlorophylls surrounded by an aqueous fluid in the chloroplasts under incoherent unpolarized sunlight. Learning from the chiral fluid biosystem, we designed artificial polymer aggregates of three highly luminescent helical polysilanes, 1-S, 2-S, and 2-R (Chart 1). Under specific conditions (molecular weights and good-and-poor solvent ratio), 1-S aggregates with ∼5 μm in organic fluid generated an efficient circularly polarized luminescence (CPL) with gCPL = −0.7 at 330 nm while retaining a high quantum efficiency (ΦPL) ∼53% at room temperature under incoherent unpolarized photoexcitation at 290 nm. This huge gCPL value was the consequence of the intense bisignate circularly dichroism (CD) signals (gCD = −0.35 at 325 nm and +0.31 at 313 nm) due to coupled oscillators with electric-dipole-allowed-transition origin. Also, 2-S and 2-R aggregates gav...