Realization of High-Performance Self-Powered Polarized Photodetection with Large Temperature Window in a 2D Polar Perovskite.

Polarization photodetection taking advantage of the anisotropy of 2D materials shines brilliantly in optoelectronic fields owing to differentiating optical information. However, the previously reported polarization detections are mostly dependent on external power sources, which is not conducive to device integration and energy conservation. Herein, a 2D polar perovskite (CBA)2CsPb2Br7 (CCPB, CBA = 4-chlorobenzyllamine) has been successfully synthesized, which shows anticipated bulk photovoltaic effect (BPVE) with an open-circuited photovoltage up to ≈0.2 V. Devices based on CCPB monomorph fulfill a fascinating self-powered polarized photodetection with a large polarization ratio of 2.7 at room temperature. Moreover, CCPB features a high phase-transition temperature (≈475 K) which prompts such self-powered polarized photodetection in a large temperature window of device operation, since BPVE generated by spontaneous polarization can only exist in the polar structure prior to the phase transition. Further computational investigation reveals the introduction of CBA+ with a large dipole moment contributes to quite large polarization (17.5 µC cm-2) and further super high phase transition temperature of CCPB. This study will promote the application of 2D perovskite materials for self-powered polarized photodetection in high-temperature conditions.

Tunable Contacts of Bi2 O2 Se Nanosheets MSM Photodetectors by Metal-Assisted Transfer Approach for Self-Powered Near-Infrared Photodetection.

Owing to the Fermi pinning effect arose in the metal electrodes deposition process, metal-semiconductor contact is always independent on the work function, which challenges the next-generation optoelectronic devices. In this work, a metal-assisted transfer approach is developed to transfer Bi2 O2 Se nanosheets onto the pre-deposited metal electrodes, benefiting to the tunable metal-semiconductor contact. The success in Bi2 O2 Se nanosheets transfer is contributed to the stronger van der Waals adhesion of metal electrodes than that of growth substrates. With the pre-deposited asymmetric electrodes, the self-powered near-infrared photodetectors are realized, demonstrating low dark current of 0.04 pA, high Ilight /Idark ratio of 380, fast rise and decay times of 4 and 6 ms, respectively, under the illumination of 1310 nm laser. By pre-depositing the metal electrodes on polyimide and glass, high-performance flexible and omnidirectional self-powered near-infrared photodetectors are achieved successfully. This study opens up new opportunities for low-dimensional semiconductors in next-generation high-performance optoelectronic devices.

Realization of In-Plane Polarized Light Detection Based on Bulk Photovoltaic Effect in A Polar Van Der Waals Crystal.

2D van der Waals materials are widely explored for in-plane polarized light detection owing to their distinctive in-plane anisotropic feature. However, most of these polarized light-sensitive devices root in their low symmetry of in-plane structure and work depending on external power sources, which greatly impedes the simplification of integrated devices and sustainable development. Bulk photovoltaic effect (BPVE), which separates photoexcited carriers via built-in electric field without an external power source and shows an angle-dependence on light polarization, is promising for self-powered polarized light detection to break through the restriction of in-plane anisotropy. Herein, a 2D lead-free van der Waals perovskite (Cl-PMA)2 CsAgBiBr7 (1, Cl-PMA = 4-Chlorobenzylamine) is successfully designed through the dimension reduction strategy. 1 exhibits BPVE with an open-circuited photovoltage up to ≈0.5 V. Driven by the BPVE, self-powered in-plane polarized light detection with a large polarization ratio of 1.3 is obtained for 1. As far as it is known, the first in-plane polarized light detection in hybrid perovskites based on BPVE is realized here. This work highlights the strategy of designing lead-free hybrid perovskite with BPVE and opens an avenue for exploiting in-plane highly sensitive polarized light detection in 2D van der Waals materials.

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.

Ferroelectricity-Driven Self-Powered Ultraviolet Photodetection with Strong Polarization Sensitivity in a Two-Dimensional Halide Hybrid Perovskite.

Polarization-sensitive ultraviolet (UV) photodetection is highly indispensable in military and civilian applications and has been demonstrated with various wide-band photodetectors. However, it still remains elusive to achieve the self-powered devices, which can be operated in the absence of external bias. Herein, for the first time, ferroelectricity-driven self-powered photodetection towards polarized UV light was successfully demonstrated in a 2D wide-band gap hybrid ferroelectric (BPA)2 PbBr4 (BPA=3-bromopropylammonium) (1). We found that the prominent spontaneous polarization in 1 results in a bulk photovoltaic effect (BPVE) of 0.85 V, that independently drives photoexcited carriers separation and transport and thus supports self-powered ability. This self-powered detector shows strong polarization sensitivity to linearly polarized UV illumination with a polarization ratio up to 6.8, which is superior to that of previously reported UV-polarized photodetectors (ZnO, GaN, and GeS2 ).

Toward Smart, Flexible, and Omnidirectional Self-Powered Photodetection by an All-Solution-Processed In2O3/Pbl2 Heterojunction.

Amorphous In2O3 film is emerging as a promising oxide semiconductor for next-generation electronics and optoelectronics owing to high mobility and wide band gap. However, the persistent photocurrent phenomenon and high carrier concentration in amorphous In2O3 film are challenging the photodetection performances, resulting in a long response time and low Ilight/Idark ratio. In this work, the In2O3/PbI2 heterojunction is constructed by an all-solution synthesis process to inhibit the persistent photocurrent phenomenon and large dark current. Benefiting from the built-in electric field at the heterojunction interface, the In2O3/PbI2 heterojunction photodetector exhibits excellent self-powered photodetection performances with an ultralow dark current of 10-12 A, a high Ilight/Idark ratio of 104, and fast response times of 0.6/0.6 ms. Furthermore, the entire solution synthesis process and amorphous characteristics enable the fabrication of an In2O3/PbI2 heterojunction photodetector on arbitrary substrates to realize specific functions. When configured onto the polyimide substrate, the In2O3/PbI2 heterojunction photodetector shows excellent mechanical flexibility, bending endurance, and photoresponse stability. When implanted onto the transparent substrate, the In2O3/PbI2 heterojunction photodetector exhibits an outstanding omnidirectional self-powdered photodetection performance and imaging capability. All results pave the way for an all-solution-processed amorphous In2O3 film in advanced high-performance photodetectors.

Self-Powered Photodetector Based on Ag/CH3NH3PbI3/C Asymmetric Dual-Terminal Device.

CH3NH3PbI3 is capable of exhibiting a superior photoresponse to visible light, but its self-powered devices are typically formed through p-n junctions. In this study, we fabricated a Ag/CH3NH3PbI3/C dual-terminal asymmetric electrode device using a single CH3NH3PbI3 perovskite micro/nanowire, enabling both the photoresponse and self-powered characteristics of CH3NH3PbI3 to visible light. Compared with traditional p-n junction devices, this simple device demonstrates enhanced interface photovoltaic effects by optimizing the combination of the Ag electrode with CH3NH3PbI3, resulting in superior self-powered characteristics. Under low bias voltage, the device achieves a significant on/off ratio of 103, with superior sensitivity and responsivity as well as a maximum rectification ratio of about 12. The photogenerated voltage and current reach approximately 0.8 V and 2 nA, respectively. This simple, compact, and self-powered asymmetric device exhibits great potential for applications in self-powered optoelectronics and wearable devices. This research provides a promising approach for recognizing and utilizing surface state effects in single nanoscale structures.

High-Performance, Polarization-Sensitive, Long-Wave Infrared Photodetection via Photothermoelectric Effect with Asymmetric van der Waals Contacts.

Long-wavelength infrared (LWIR) photodetection is important for heat-seeking technologies, such as thermal imaging, all-weather surveillance, and missile guidance. Among various detection techniques, photothermoelectric (PTE) detectors are promising in that they can realize ultra-broadband photodetection at room temperature without an external power supply. However, their performance in terms of speed, responsivity, and noise level in the LWIR regime still needs further improvement. Here, we demonstrated a high-performance PTE photodetector based on low-symmetry palladium selenide (PdSe2) with asymmetric van der Waals contacts. The temperature gradient induced by asymmetric van der Waals contacts even under global illumination drives carrier diffusion to produce a photovoltage via the PTE effect. A responsivity of over 13 V/W, a response time of ∼50 µs, and a noise equivalent power of less than 7 nW/Hz1/2 are obtained in the 4.6-10.5 µm regime at room temperature. Furthermore, due to the anisotropic absorption of PdSe2, the detector exhibits a linear polarization angle sensitive response with an anisotropy ratio of 2.06 at 4.6 µm and 1.21 at 10.5 µm, respectively. Our proposed device architecture provides an alternative strategy to design high-performance photodetectors in the LWIR regime by utilizing van der Waals layered materials.