Tuning the Visible Circularly Polarized Luminescence in Highly Emissive Chiral Terbium and Europium Chlorides

Abstract

Chiral hybrid metal halides have become increasingly popular for their high structural tunability and exceptional optoelectronic properties. Incorporating rare-earth (RE) metals into the structural units and inheriting their pure emission characteristics are of great interests and importance. Here, we report two pairs of new isostructural chiral hybrid RE chlorides based on RE metals Tb3+ and Eu3+, crystallizing in the non-centrosymmetric space group P212121. The circular dichroism (CD) and circularly polarized luminescence (CPL) spectra of these materials exhibit mirror-like symmetrical shapes, further confirming the polar nature and highly controllable selectivity due to the use of R- or S-methylpiperazinium cations. The CPL emissions have signature sharp signals due to the RE emissions, with dissymmetry factors │glum│ of ~4×10−3 for R/S-Tb and ~6×10−3 for R/S-Eu, respectively. Furthermore, these materials show superior emission properties in visible regions, with a high photoluminescence quantum yield (PLQY) of ~80% for R/S-Tb and ~30% for R/S-Eu. In addition, the Tb-Eu alloyed compounds demonstrate excitation-dependent tunable CPL in the visible region with green, yellow, or red emissions, which can be applied in anti-counterfeiting and information encryption. The highly tunable CPL emission and diversification of chiral RE metal halides in this work offer new routes for chiroptical optoelectronics.