Constructing diverse switchable circularly polarized luminescence via a single azobenzene polymer film

Recently circularly polarized luminescence (CPL) materials have attracted significant interest. Introducing reversible dynamic property to these materials has been a key focus in cutting-edge fields, such as in high-level information encryption. Here, we provided a novel and general strategy involving handedness-selective filtration and ground-state chiral self-recovery (CSR) in double film system to address this issue. Based on this strategy, we achieved CPL switch through the reversible modulation of ground-state chirality including absorption and scattering circular dichroism (CD) signals over the full UV-visible wavelength range (365-700 nm) in a single azobenzene polymer (PAzo) film. More importantly, by flexibly changing the type of fluorescent films, it is convenient to achieve general excited-state CSR, that is reversible switching of full-color including ideal white (CIE coordinate (0.33, 0.33)), as well as room-temperature phosphorescent CPL. All these CPL signals without almost any intensity decay after three cycles of on-and-off switching. Experimental results indicated that the trans-cis isomerization and ordered rearrangement of azobenzene units in PAzo film were the fundamental reasons for realizing CPL switching. Finally, based on this system we achieved dynamic visual encryption and decryption process including multiple decryption methods. This study provides an effective method for constructing a universally applicable chiroptical switch in excited state.