Multifunctional\nChiral 2D Lead Halide Perovskites\nwith Circularly Polarized Photoluminescence and Piezoelectric Energy\nHarvesting Properties

Abstract

Introducing\nthe chiral spacers to two-dimensional (2D) lead halide\nperovskites (LHPs) enables them to exhibit circularly polarized photoluminescence\n(CPPL), which could have applications in chiral-optics and spintronics.\nDespite that a great deal of effort has been made in this field, the\nreported polarization degree of CPPL at ambient conditions is still\nvery limited, and the integration of multiple functionalities also\nremains to be explored. Here we report the structures, CPPL, and piezoelectric\nenergy harvesting properties of chiral 2D LHPs, [<i>R-</i>1-(4-bromophenyl)­ethylaminium]₂PbI₄ (<i>R-</i>[BPEA]₂PbI₄) and [<i>S-</i>1-(4-bromophenyl)­ethylaminium]₂PbI₄ (<i>S-</i>[BPEA]₂PbI₄). Our results show that\nthese chiral perovskites are direct bandgap semiconductors and exhibit\nCPPL centered at ∼513 nm with a maximum degree of polarization\nof up to 11.0% at room temperature. In addition, the unique configurational\narrangement of the chiral spacers is found to be able to reduce the\ninterlayer π–π interactions and consequently result\nin strong electron–phonon coupling. Furthermore, the intrinsic\nchirality of both <i>R-</i>[BPEA]₂PbI₄ and <i>S-</i>[BPEA]₂PbI₄ enables\nthem to be piezoelectric active, and their composite films can be\napplied to generate voltages and currents up to ∼0.6 V and\n∼1.5 μA under periodic impacting with a strength of 2\nN, respectively. This work not only reports a high degree of CPPL\nbut also demonstrates piezoelectric energy harvesting behavior for\nrealizing multifunctionalities in chiral 2D LHPs.