Multifunctional Chiral 2D Lead Halide Perovskites with Circularly Polarized Photoluminescence and Piezoelectric Energy Harvesting Properties

Abstract

Introducing the chiral spacers to two-dimensional (2D) lead halide perovskites (LHPs) enables them to exhibit circularly polarized photoluminescence (CPPL), which could have applications in chiral-optics and spintronics. Despite that a great deal of effort has been made in this field, the reported polarization degree of CPPL at ambient conditions is still very limited, and the integration of multiple functionalities also remains to be explored. Here we report the structures, CPPL, and piezoelectric energy harvesting properties of chiral 2D LHPs, [R-1-(4-bromophenyl)­ethylaminium]2PbI4 (R-[BPEA]2PbI4) and [S-1-(4-bromophenyl)­ethylaminium]2PbI4 (S-[BPEA]2PbI4). Our results show that these chiral perovskites are direct bandgap semiconductors and exhibit CPPL centered at ∼513 nm with a maximum degree of polarization of up to 11.0% at room temperature. In addition, the unique configurational arrangement of the chiral spacers is found to be able to reduce the interlayer π–π interactions and consequently result in strong electron–phonon coupling. Furthermore, the intrinsic chirality of both R-[BPEA]2PbI4 and S-[BPEA]2PbI4 enables them to be piezoelectric active, and their composite films can be applied to generate voltages and currents up to ∼0.6 V and ∼1.5 μA under periodic impacting with a strength of 2 N, respectively. This work not only reports a high degree of CPPL but also demonstrates piezoelectric energy harvesting behavior for realizing multifunctionalities in chiral 2D LHPs.

Chiral Rashba Ferroelectrics for Circularly Polarized Light Detection

“…[ 11b ] It has a calculated E RD value of 6.3 meV, [ 28 ] about half the value of 1 R / S . ( R / S ‐BPEA) 2 PbI 4 adopts a chiral&polar space group C 2 with a P of ≈7% and a g Iph of 0.13 at 298 K. [ 17b,34 ] The Dion–Jacobson MHP (4AMP)PbI 4 takes a polar space group Pc with a P of ≈13% and an estimated g Iph of 0.18 at 298 K. [ 23c ] It has an experimented E RD value of 90 meV, comparable to our experimental value of 1 R / S (97 meV). [ 23b,c ] The above data show that although the g Iph of perovskite single crystals is much larger than the g CD , its value is roughly equivalent to the P .…”

Spin-polarized excitons and charge carriers in chiral metal halide semiconductors

“…An aqueous phase synthesis method 50 was used by adding a small proportion of MA + during the synthesis process, and MA + does not change the composition and structure of (R/S-MBA) 2 PbI 4 , but induces (R/S-MBA) 2 PbI 4 to produce a CPL signal at room temperature, which may be attributed to the passivation effect of the MA + additive and the average DP of (R-MBA) 2 PbI 4 and (S-MBA) 2 PbI 4 was 13.7% and 11.4%. 27 The CPL capability of (R/S-MBA) 2 PbI 4 27,51 and (R/S-1-(4-bromophenyl) ethyl-amine) 2 PbI 4 52 reaches DP > 10% at room temperature, but there is still plenty of room for DP to be improved up to the theoretical maximum DP value of 1.…”

“…Meanwhile, ferroelectrics must have piezoelectric properties, and there are recent reports on the piezoelectricity of ( R / S -1-(4-bromophenyl)ethylamine) 2 PbI 4 . 52 CMHS ferroelectrics possess not only ferroelectricity, but also semiconducting properties 103 (Fig. 9a).…”

Chiral 2D Cu(I) Halide Frameworks

“…15−19 Chirality transfer from organic modules to inorganic moieties can be effectively realized not only through the formation of chemical bonds but also through spatial interactions. 20,21 Intrinsic chirality introduced in metal hybrid materials will generally break the symmetry, leading to novel chirality-related optoelectronic properties, such as circular dichroism (CD), 20,22 circularly polarized luminescence (CPL), 23 second harmonic generation (SHG), 24 pyroelectricity, 25 piezoelectricity, 26 and ferroelectricity. 27 In addition, due to the interaction between chirality and spin, the introduction of chirality into organic−inorganic hybrid metal halides with a strong spin orbit coupling system (Pb and I) also has broad application prospects in spintronics.…”

“…Advanced multifunctional materials that integrate multiple properties in a single crystalline material have attracted a tremendous amount of research interest. − In recent years, hybrid organic–inorganic metal halides have been considered promising functional materials because of their structural diversity and extraordinary photophysical properties. − Due to the tunable compositions and flexible crystal structures of hybrid organic–inorganic metal halides, chiral moieties can be rationally introduced into the system as ligands or templating cations, enabling the construction of multifunctional materials. − Chirality transfer from organic modules to inorganic moieties can be effectively realized not only through the formation of chemical bonds but also through spatial interactions. , Intrinsic chirality introduced in metal hybrid materials will generally break the symmetry, leading to novel chirality-related optoelectronic properties, such as circular dichroism (CD), , circularly polarized luminescence (CPL), second harmonic generation (SHG), pyroelectricity, piezoelectricity, and ferroelectricity . In addition, due to the interaction between chirality and spin, the introduction of chirality into organic–inorganic hybrid metal halides with a strong spin orbit coupling system (Pb and I) also has broad application prospects in spintronics. , …”