Multispectral and Circular Polarization-Sensitive Carbon Dot-Polydiacetylene Capacitive Photodetector.

Multispectral photodetectors (MSPs) and circularly polarized light (CPL) sensors are important in opto-electronics, photonics, and imaging. A capacitive photodetector consisting of an interdigitated electrode coated with carbon dot/anthraquinone-polydiacetylene is constructed. Photoexcitation of the carbon dots induces transient electron transfer to the anthraquinone moieties, and concomitant change in the film dielectric constant and recorded capacitance. This unique photodetection mechanism furnishes wavelength selectivity that is solely determined by the absorbance of the carbon dots incorporated in the anthraquinone-polydiacetylene matrix. Accordingly, employing an array of polymerized-anthraquinone photodetector films comprising carbon dots (C-dots) exhibiting different excitation wavelengths yielded optical "capacitive fingerprints" in a broad spectral range (350-650 nm). Furthermore, circular light polarization selectivity is achieved through chiral polymerization of the polydiacetylene framework. The carbon dot/anthraquinone-polydiacetylene capacitive photodetector features rapid photo-response, high fidelity, and recyclability as the redox reactions of anthraquinone are fully reversible. The carbon dot/anthraquinone-polydiacetylene platform is inexpensive, easy to fabricate, and consists of environmentally friendly materials.

Chiral Non-Fullerene Acceptor Enriched Bulk Heterojunctions Enable High-Performance Near-Infrared Circularly Polarized Light Detection.

Organic photodetectors that can sensitively convert near-infrared (NIR) circularly polarized light (CPL) into modulable electrical signals have promising applications in spectroscopy, imaging, and communications. However, the preparation of chiral NIR organic photodetectors with simultaneously high dissymmetry factor, responsivity, detectivity, and response speed is challenging. Here, direct CPL detectors based on the bulk heterojunctions (BHJs) of chiral BTP-4Cl non-fullerene acceptor with dilute achiral PM6 donor are constructed, which successfully address these issues. The chiral acceptor-enriched BHJs with a donor/acceptor ratio of 1/10 achieve an optimal trade-off between chiroptical properties and optoelectronic performance. The supramolecular chirality from the acceptor aggregates provides the BHJs with a true absorption dissymmetry factor (gabs ) of ±0.02 at 830 nm, the highest value among NIR-sensitive detectors, which endows the photodetector with a photocurrent dissymmetry factor (gsc ) of ±0.03. Impressively, the photodetector demonstrates an external quantum efficiency as high as 60%, a responsivity of 0.4 A W-1 , a detectivity of 3 × 1011 Jones (based on noise current), and a fast response speed on the microsecond scale with the -3 dB bandwidth over 7000 Hz in the NIR region. This study exhibits a promising strategy for building high-performing direct NIR CPL detectors by introducing supramolecular chirality into BHJs.

Heterogeneous Integration of Chiral Lead-Chloride Perovskite Crystals with Si Wafer for Boosted Circularly Polarized Light Detection in Solar-Blind Ultraviolet Region.

Chiral hybrid organic-inorganic perovskites (HOIPs) have been well developed for circularly polarized light (CPL) detection, while new members that target at solar-blind ultraviolet (UV) region remain completely unexplored. Here, an effective design strategy to demonstrate circular polarization-sensitive solar-blind UV photodetection by growing wide-bandgap chiral HOIP [(R)-MPA]2 PbCl4 ((R)-MPA = methylphenethylammonium) single crystals onto silicon wafers, with well-defined heterostructures, is reported. The solid mechanical and electrical connection between the chiral HOIP and silicon wafer results in strong built-in electric field at heterojunction, providing a desirable driving force for separating/transporting carriers generated under CPL excitation at 266 nm. Unexpectedly, during such a transport process, not only the chirality of HOIP crystal is transferred to the heterostructure, but also the circular polarization sensitivity is significantly amplified. Consequently, anisotropy factor of the resultant detectors can reach up to 0.4 at zero bias, which is much higher than that of the pristine single-phase chiral HOIP (≈0.1), reaching the highest among the reported CPL-UV photodetectors. As far as we know, the integration of chiral HOIP crystals with silicon technology is unprecedent, which paves a way for designing boosted-performance CPL detectors in solar-blind UV region as well as for other advanced optoelectronic devices.

Chiral Lead-Free Hybrid Perovskites for Self-Powered Circularly Polarized Light Detection.

Metal-halide perovskites are recently emerging as the promising alternative for CPL detection owing to their CPL-sensitive property induced by chiral organics and efficient charge transport of inorganic frameworks. However, most of these reported chiral perovskites involve high concentrations of toxic Pb which will become the potential bottleneck for their further application. Herein, we successfully developed two lead-free halide double perovskites, [(R)-ß-MPA]4 AgBiI8 ((R)-ß-MPA=(R)-(+)-ß-methylphenethylammonium, 1-R), and [(S)-ß-MPA]4 AgBiI8 ((S)-ß-MPA=(S)-(-)-ß-methylphenethylammonium, 1-S). Circular dichroism measurements reveal that these perovskites exhibit notable chirality induced by organic cations to distinguish different polarization states of CPL photons. Significantly, they present unique chiral polar photovoltaic, and resulting self-powered CPL detection without an external power source is unprecedentedly achieved. Furthermore, an anisotropy factor up to 0.3 is acquired for the self-powered CPL detection, reaching the highest value among reported chiral perovskites. This work suggests hybrid double perovskites are promising photoelectronic candidates, and provides a new approach for exploring new "green" circularly polarized light-sensitive materials with high performance.

Pyro-Phototronic Effect Induced Circularly Polarized Light Detection with a Broadband Response.

Photopyroelectric-based circularly polarized light (CPL) detection, coupling the pyro-phototronic effect and chiroptical phenomena, has provided a promising platform for high-performance CPL detectors. However, as a novel detection strategy, photopyroelectric-based CPL detection is currently restricted by the short-wave optical response, underscoring the urgent need to extend its response range. Herein, visible-to-near-infrared CPL detection induced by the pyro-phototronic effect is first realized in chiral-polar perovskites. Specifically, chiral-polar multilayered perovskites (S-BPEA)2FAPb2I7 (1-S, S-BPEA = (S)-1-4-Bromophenylethylammonium, FA = formamidinium) with spontaneous polarization shows intrinsic pyroelectric and photopyroelectric performance. Strikingly, combining its merits of the pyro-phototronic effect and intrinsic wide-spectrum spin-selective effect, chiral multilayered 1-S presents efficient photopyroelectric-based broadband CPL detection performance spanning 405-785 nm. This research first realizes photopyroelectric-based infrared CPL detection and also sheds light on developing high-performance broadband CPL detectors based on the pyro-phototronic effect in the fields of optics, optoelectronics, and spintronics.

Self-Powered Circularly Polarized Light Detection Enabled by Chiral Two-Dimensional Perovskites with Mixed Chiral-Achiral Organic Cations.

Direct detection of circularly polarized light (CPL) holds great promise for the development of various optical technologies. Chiral 2D organic-inorganic halide perovskites make it possible to fabricate CPL-sensitive photodetectors. However, selectively detecting left-handed circularly polarized (LCP) and right-handed circularly polarized (RCP) light remains a significant challenge. Herein, we demonstrate a greatly enhanced distinguishability of photodiode-type CPL photodetectors based on chiral 2D perovskites with mixed chiral aryl (R)-(+),(S)-(-)-α-methylbenzylammonium (R,S-MBA) and achiral alkyl n-butylammonium (nBA) cations. The (R,S-MBA0.5nBA0.5)2PbI4 perovskites exhibit a 10-fold increase in circular dichroism signals compared to (R,S-MBA)2PbI4 perovskites. The CPL photodetectors based on the mixed-cation perovskites exhibit self-powered capabilities with a specific detectivity of 2.45 × 1012 Jones at a 0 V bias. Notably, these devices show high distinguishability (gres) factors of -0.58 and +0.54 based on (R,S-MBA0.5nBA0.5)2PbI4 perovskites, respectively, surpassing the performance of (R-MBA)2PbI4-based devices by over 3-fold and setting a record for CPL detectors based on chiral 2D n = 1 perovskites.

Regulating Circularly Polarized Light Detection via Polar-Phase Transition in Alternating Chiral-Achiral Cations Intercalation-Type Hybrid Perovskites.

Circularly polarized light (CPL) detection has wide applications in many fields, where the anisotropy factor (gIph ) is an important indicator to characterize the CPL detection performance. So far, many materials with high gIph have been reported, however, the exploration of the regulation of gIph is still in its infancy. Herein, two novel alternating chiral-achiral cations intercalation-type chiral hybrid perovskites (CHPs), named (R/S-1-phenylpropylamine)(propylamine)PbBr4 (1-R/S), exhibit above room-temperature (RT) polar-phase transition, which greatly regulates the gIph value. The gIph of 1-R is 0.04 in high-temperature phase chiral non-polar (P21 21 21 ) by applying 5 V bias, interestingly, with the temperature decrease, the gIph value in low-temperature phase chiral polar (P21 ) gradually increases (0.22@360K, 0.40@340K, 0.47@320K), and finally reaches a maximum of 0.5 at RT. Such value is not only the highest among 2D CHPs to date, but presents a 12.5-fold amplification compared with 0.04. Further, this rare phenomenon should be attributed to the built-in electric field induced by the polar photovoltaic effect, which sheds light on further obtaining CHPs with large gIph .

Semi-Transparent, Chiral Organic Photodiodes with Incident Direction-Dependent Selectivity for Circularly Polarized Light.

Detection of the circular polarization of light is possible using chiral semiconductors, yet the mechanisms remain poorly understood. Semi-transparent chiral photodiodes allow for a simple experiment to investigate the basis of their selectivity: changing the side from which the diode is illuminated. A reversal of circular selectivity is observed in photocurrent generation when changing the direction of illumination on organic, bulk-heterojunction cells. The change in selectivity can be explained by a space-charge limitation on the collection of photocarriers in combination with preferential absorption of one of the circular polarizations of near-infrared light by the chiral non-fullerene acceptor. The space-charge limitation is supported by detailed measurements of frequency and intensity dependence of dc and ac photocurrents.

Metal Halide Perovskite Photo-Field-Effect Transistors with Chiral Selectivity.

Organic-inorganic (hybrid) metal halide perovskites (MHPs) incorporating chiral organic ligand molecules are naturally sensitive to left- and right-handed circular polarized light, potentially enabling selective circular polarized photodetection. Here, the photoresponses in chiral MHP polycrystalline thin films made of ((S)-(-)-α-methyl benzylamine)2PbI4 and ((R)-(+)-α-methyl benzylamine)2PbI4, denoted as (S-MBA)2 PbI4 and (R-MBA)2PbI4, respectively, are investigated by employing a thin-film field-effect transistor (FET) configuration. The left-hand-sensitive films made of (S-MBA)2PbI4 perovskite show higher photocurrent under left-handed circularly polarized (LCP) light than under right-handed circularly polarized (RCP) illumination under otherwise identical conditions. Conversely, the right-hand-sensitive films made of (R-MBA)2PbI4 are more sensitive to RCP than LCP illumination over a wide temperature range of 77-300 K. Furthermore, based on FET measurements, we found evidence of two different carrier transport mechanisms with two distinct activation energies in the 77-260 and 280-300 K temperature ranges, respectively. In the former temperature range, shallow traps are dominant in the perovskite film, which are filled by thermally activated carriers with increasing temperature; in the latter temperature range, deep traps with one order of magnitude larger activation energy dominate. Both types of chiral MHPs show intrinsic p-type carrier transport behavior regardless of the handedness (S or R) of these materials. The optimal carrier mobility for both handedness of material is around (2.7 ± 0.2) × 10-7 cm2 V-1 s-1 at 270-280 K, which is two magnitudes larger than those reported in nonchiral perovskite MAPbI3 polycrystalline thin films. These findings suggest that chiral MHPs can be an excellent candidate for selective circular polarized photodetection applications, without additional polarizing optical components, enabling simplified construction of detection systems.

Fused-Ring Electron-Acceptor Single Crystals with Chiral 2D Supramolecular Organization for Anisotropic Chiral Optoelectronic Devices.

Supramolecular chiral organization gives π-conjugated molecules access to fascinating specific interactions with circularly polarized light (CPL). Such a feature enables the fabrication of high-performance chiral organic electronic devices that detect or emit CPL directly. Herein, it is shown that chiral fused-ring electron-acceptor BTP-4F single-crystal-based phototransistors demonstrate distinguished CPL discrimination capability with current dissymmetry factor exceeding 1.4, one of the highest values among state-of-the-art direct CPL detectors. Theoretical calculations prove that the chirality at the supramolecular level in these enantiomeric single crystals originates from chiral exciton coupling of a unique quasi-2D supramolecular organization consisting of interlaced molecules with opposite helical conformation. Impressively, such supramolecular organization produces a higher dissymmetry factor along the preferred growth direction of the chiral single crystals in comparison to that of the short axis direction. Furthermore, the amplified, inverted, and also anisotropic current dissymmetry compared to optical dissymmetry is studied by finite element simulations. Therefore, a unique chiral supramolecular organization that is responsible for the excellent chiroptical response and anisotropic electronic properties is developed, which not only enables the construction of high-performance CPL detection devices but also allows a better understanding of the structure-property relationships in chiral organic optoelectronics.

Toward Efficient Two-Photon Circularly Polarized Light Detection through Cooperative Strategies in Chiral Quasi-2D Perovskites.

Organic-inorganic hybrid perovskites carry unique semiconducting properties and advanced flexible crystal structures. These characteristics of organic-inorganic hybrid perovskites create a promising candidacy for circularly polarized light (CPL) detection. However, CPL detections based on chiral perovskites are limited to UV and visible wavelengths. The natural quantum well structures of layered hybrid perovskites generate strong light-matter interactions. This makes it possible to achieve near-infrared (NIR) CPL detection via two-photon absorption in the sub-wavelength region. In this study, cooperative strategies of dimension increase and mixed spacer cations are used to obtain a pair of chiral multilayered perovskites (R-ß-MPA)EA2 Pb2 Br7 and (S-ß-MPA)EA2 Pb2 Br7 (MPA = methylphenethylammonium and EA = ethylammonium). The distinctive bi-cations interlayer and multilayered inorganic skeletons provide enhanced photoconduction. Moreover, superior photoconduction leads to the prominent NIR CPL response with a responsivity up to 8.1 × 10-5 A W-1 . It is anticipated that this work can serve as a benchmark for the fabrication and optimization of efficient NIR CPL detection by simple chemical design.

Chiral Rashba Ferroelectrics for Circularly Polarized Light Detection.

Direct detection of circularly polarized light (CPL) is a challenging task due to limited materials and ambiguous structure-property relationships that lead to low distinguishability of the light helicities. Perovskite ferroelectric semiconductors incorporating chirality provide new opportunities in dealing with this issue. Herein, a pair of 2D chiral perovskite ferroelectrics is reported, which have enhanced CPL detection performance due to interplays among lattice, photon, charge, spin, and orbit. The chirality-transfer-induced chiral&polar ferroelectric phase enhances the asymmetric nature of the photoactive sublattice and achieves a switchable self-powered detection via the bulk photovoltaic effect. The single-crystal-based device exhibits a CPL-sensitive detection performance under 430 nm with an asymmetric factor of 0.20 for left- and right-CPL differentiation, about two times that of the pure chiral counterparts. The enhanced CPL detection performance is ascribed to the Rashba-Dresselhaus effect that originates from the bulk inversion asymmetry and strong spin-orbit coupling, shown with a large Rashba coefficient, which is demonstrated by density functional theory calculation and circularly polarized light excited photoluminescence measurement. These results provide new perspectives on chiral Rashba ferroelectric semiconductors for direct CPL detection and ferroelectrics-based chiroptics and spintronics.

Chiral Hybrid Perovskite Single-Crystal Nanowire Arrays for High-Performance Circularly Polarized Light Detection.

Circularly polarized light (CPL) detection has emerged as a key technology for various optoelectronics. Chiral hybrid perovskites (CHPs) that combine CPL-sensitive absorption induced by chiral organic ligands and superior photoelectric properties of perovskites are promising candidates for direct CPL detection. To date, most of the CHP detectors are made up of polycrystalline thin-film, which results in a rather limited discrimination of CPL due to the existence of redundant impurities and intrinsic defect states originating from rapid crystallization process. Here, it is developed a direct CPL detector with high photocurrent and polarization selectivity based on low-defect CHP single-crystal nanowire arrays. Large-scale CHP nanowires are obtained through a micropillar template-assisted capillary-bridge rise approach. Thanks to the high crystallinity and ordered crystallographic alignment of these arrays, a CPL photodetector with high light on/off ratio of 1.8 × 104 , excellent responsivity of 1.4 A W-1 , and an outstanding anisotropy factor of 0.24 for photocurrent has been achieved. These results would provide useful enlightenment for direct CPL detection in high-performance chiral optoelectronics.

Direct Detection of Circularly Polarized Light Using Chiral Copper Chloride-Carbon Nanotube Heterostructures.

The emergent properties of chiral organic-inorganic hybrid materials offer opportunities in spin-dependent optoelectronic devices. One of the most promising applications where spin, charge, and light are strongly coupled is circularly polarized light (CPL) detection. However, the performance of state-of-the-art CPL detectors using chiral hybrid metal halide semiconductors is still limited by the low anisotropy factor, poor conductivity, and limited photoresponsivity. Here, we synthesize 0D chiral copper chloride hybrids, templated by chiral methylbenzylammonium (R/S-MBA), i.e., (R-/S-MBA)2CuCl4, that display circular dichroism for the ligand-to-metal charge transfer transition with an absorption anisotropy factor (gCD) among the largest reported for chiral metal halide semiconductor hybrids. To circumvent the poor conductivity of the unpercolated inorganic framework of this chiral absorber, we develop a direct CPL detector that utilizes a heterojunction between the chiral (MBA)2CuCl4 absorber layer and a semiconducting single-walled carbon nanotube (s-SWCNT) transport channel. Our chiral heterostructure shows high photoresponsivity of 452 A/W, a competitive anisotropy factor (gres) of up to 0.21, a current response in microamperes, and low working voltage down to 0.01 V. Our results clearly demonstrate a useful strategy toward high-performance chiral optoelectronic devices, where a nanoscale heterostructure enables direct CPL detection even for highly insulating chiral materials.

Surface-Doped Quasi-2D Chiral Organic Single Crystals for Chiroptical Sensing.

Chiral organic optoelectronics using circularly polarized light (CPL) as the key element in the photonic signal has recently emerged as a next-generation photonic technology. However, it remains challenging to simultaneously achieve high polarization selectivity and superior optoelectronic performance. Supramolecular two-dimensional (2D) chiral organic single crystals may be good candidates for this purpose due to their defect-free nature, molecular diversity, and morphologies. Here, quasi-2D single crystals of chiral perylene diimides with parallelogram and triangle/hexagon morphologies have been selectively fabricated via self-assembly using different cosolvent systems. These materials exhibit amplified circular dichroism (CD) spectral signals, due to their molecular packing modes and supramolecular chirality. Through molecular surface n-doping using hydrazine, chiral single crystals exhibit electron mobility surpassing 1.0 cm2 V-1 s-1, which is one of the highest among chiral organic semiconductors, and excellent optoelectronic functions. Theoretical calculations reveal that the radical anions formed by n-doping increase the electron affinity and/or reduce the energy gap, thus facilitating electron transport. More importantly, the doped organic chiral crystals selectively discriminate CPL handedness with a high anisotropy factor of photoresponsivity (∼0.12). These results demonstrate that surface-doped quasi-2D chiral organic single crystals are highly promising for chiral optoelectronics.

Chiral 2D Perovskites with a High Degree of Circularly Polarized Photoluminescence.

Chiral materials are of particular interest and have a wide range of potential applications in life science, material science, spintronic, and optoelectronic devices. Two-dimensional (2D) hybrid organic-inorganic lead halide perovskites have attracted increasing attention. Incorporating the chiral organic ligands into the layered lead iodide frameworks would introduce strong chirality in pure 2D perovskites for potential applications in circularly polarized light (CPL) emission and detection; nonetheless, studies on those aspects are still in their infancy. Here, we report on the strong CPL emission and sensitive CPL detection in the visible-wavelength range in pure chiral ( R-/ S-MBA)2PbI4 (MBA = C6H5C2H4NH3) 2D perovskites, which are successfully synthesized with a needle shape and millimeter size by incorporating the chiral molecules. The chiral 2D perovskites ( R-MBA)2PbI4 and ( S-MBA)2PbI4 exhibit an average degree of circularly polarized photoluminescence (PL) of 9.6% and 10.1% at 77 K, respectively, and a maximum degree of the circularly polarized PL of 17.6% is achieved in ( S-MBA)2PbI4. The degree of circularly polarized PL dramatically decreases with increasing temperature, implying that the lattice distortion induced by the incorporated chiral molecules and/or temperature-dependent spin flipping might be the origin for the observed chirality. Finally, CPL detection has been achieved with decent performance in our chiral 2D perovskite microplate/MoS2 heterostructural devices. The high degree of the circularly polarized PL and excellent CPL detection together with the layered nature of pure chiral 2D perovskites enables them to be a class of very promising materials for developing and exploring spin associated electronic devices based on the chiral 2D perovskites.

Aqueous Synthesis of Low-Dimensional Lead Halide Perovskites for Room-Temperature Circularly Polarized Light Emission and Detection.

Low-dimensional lead halide perovskite materials are an emerging class of solution-processable semiconductors with promising potential applications in optoelectronic devices. Unfortunately, it is impossible to synthesize high-crystalline-quality low-dimensional perovskite single crystals without using chemotoxic solutions such as dimethylformamide/dimethyl sulfoxide or applying heating. Herein we report an economical and universal aqueous method to synthesize 2D layered and 1D chain perovskite single crystals at room temperature. The resultant chiral 2D perovskites can efficiently and selectively emit and detect circularly polarized light at room temperature. The as-synthesized 1D perovskite single crystals exhibit strong quantum confinement and enhanced self-trapped states that give efficient warm circularly polarized white-light emission. This aqueous synthetic method is general for other high-quality low-dimensional lead halide perovskite single crystals, and thus our findings would motivate more fundamental investigations on low-dimensional perovskites for potential optoelectronic applications.