Visible-ultraviolet dual-band photodetectors based on an all-inorganic CsPbCl3/p-GaN heterostructure

All-inorganic metal halide perovskites (MHPs) have attracted increasing attention because of their high thermal stability and band gap tunability. Among them, CsPbCl3 is considered a promising semiconductor material for visible-ultraviolet dual-band photodetectors because of its excellent photoelectric properties and suitable band gap value. In this work, we fabricated a visible-ultraviolet dual-band photodetector based on a CsPbCl3/p-GaN heterojunction using the spin coating method. The formation of the heterojunction enables the device to exhibit obvious dual-band response behavior at positive and negative bias voltages. At the same time, the dark current of the device can be as low as 2.42 × 10-9 A, and the corresponding detection rate can reach 5.82 × 1010 Jones. In addition, through simulation calculations, it was found that the heterojunction has a type II energy band arrangement, and the heterojunction response band light absorption is significantly enhanced. The type II energy band arrangement will separate electron-hole pairs more effectively, which will help improve device performance. The successful implementation of visible-ultraviolet dual-band photodetectors based on a CsPbCl3/p-GaN heterojunction provides guidance for the application of all-inorganic MHPs in the field of multi-band photodetectors.

Spin Texture Sensitive Photodetection by Dion-Jacobson Tin Halide Perovskites

The organic spacer molecule is known to regulate the optoelectronic properties of two-dimensional (2D) perovskites. We show that the spacer layer thickness determines the nature of optical transitions, direct or indirect, by controlling the structural properties of the inorganic layer. The spin-orbit interactions lead to different electron spin orientations for the states associated with the conduction band minimum (CBM) and the valence band maximum (VBM). This leads to a direct as well as an indirect component of the transitions, despite them being direct in momentum space. The shorter chains have a larger direct component, leading to a better optoelectronic performance. The mixed halide Sn2+ Dion-Jacobson (DJ) perovskite with the shortest 4-C diammonium spacer outshines the photodetection parameters of those having longer (6-C and 8-C) spacers and the corresponding Ruddlesden-Popper (RP) phases. The DJ system with a 4-C spacer and equimolar Br/I embodies an unprecedentedly high responsivity of 78.1 A W-1 under 3 V potential bias at 485 nm wavelength, among the DJ perovskites. Without any potential bias, this phase manifests the self-powered photodetection parameters of 0.085 A W-1 and 9.9 × 1010 jones. The unusual role of electron spin texture in these high-performance photodetectors of the lead-free DJ perovskites provides an avenue to exploit the information coded in spins for semiconductor devices without any ferromagnetic supplement or magnetic field.

Transition from Dion-Jacobson hybrid layered double perovskites to 1D perovskites for ultraviolet to visible photodetection

New perovskite phases having diverse optoelectronic properties are the need of the hour. We present five variations of R2AgM(iii)X8, where R = NH3C4H8NH3 (4N4) or NH3C6H12NH3 (6N6); M(iii) = Bi3+ or Sb3+; and X = Br- or I-, by tuning the composition of (4N4)2AgBiBr8, a structurally rich hybrid layered double perovskite (HLDP). (4N4)2AgBiBr8, (4N4)2AgSbBr8, and (6N6)2AgBiBr8 crystallize as Dion-Jacobson (DJ) HLDPs, whereas 1D (6N6)SbBr5, (4N4)-BiI and (4N4)-SbI have trans-connected chains by corner-shared octahedra. Ag+ stays out of the 1D lattice either when SbBr63- distortion is high or if Ag+ needs to octahedrally coordinate with I-. Band structure calculations show a direct bandgap for all the bromide phases except (6N6)2AgBiBr8. (4N4)2AgBiBr8 with lower octahedral tilt shows a maximum UV responsivity of 18.8 ± 0.2 A W-1 and external quantum efficiency (EQE) of 6360 ± 58%, at 2.5 V. When self-powered (0 V), (4N4)-SbI has the best responsivity of 11.7 ± 0.2 mA W-1 under 485 nm visible light, with fast photoresponse ≤100 ms.

Incorporating an Aromatic Diammonium To Assemble Bilayered Dion-Jacobson Perovskite Crystals for Weak Light Detection

Two-dimensional (2D) Dion-Jacobson (DJ) hybrid perovskites with exceptional stability and enhanced out-of-plane carrier transport are regarded as one of the competive candidates for constructing next-generation photodetectors. However, the studies of DJ hybrid perovskites on weak light detection remain scarce, and the devices based on them usually show relatively poor weak light detection ability, with a detection limit of around μW/cm². Herein, a new DJ hybrid perovskite (3AMPY)(MA)Pb₂Br₇ [3AMPY is 3-(aminomethyl)pyridinium, and MA is methylammonium] with short interlayer spacing and more lattice rigidity is obtained. The devices based on (3AMPY)(MA)Pb₂Br₇ crystals exhibit an ultrahigh sensibility to weak light at 377 and 405 nm, with an extremely low detection limit of ∼70 nW/cm². Moreover, the on/off ratios and detectivity of the devices can reach ∼10³ and ∼10¹² Jones at both 377 and 405 nm, respectively. This work highlights great potential of DJ hybrid perovskites toward weak light detection.

Formamidinium Perovskitizers and Aromatic Spacers Synergistically Building Bilayer Dion-Jacobson Perovskite Photoelectric Bulk Crystals

Two-dimensional (2D) multilayer Dion-Jacobson (DJ) phase organic inorganic hybrid perovskites (OIHPs) have attracted extensive research attention due to the high stability and excellent charge-transport properties in the optoelectronic field. However, the synthesis of 2D multilayer DJ OIHPs is still very challenging. Until now, only few multilayer DJ perovskites have been reported and most of them are based on volatile methylamine (MA) cations. Compared with MA-based OIHPs, the OIHPs constructed with formamidinium (FA) as perovskitizers not only improve the stability but also extend the light absorption range. Meanwhile, the introducing aromatic diamines as spacers could promote the electron-hole separation in such DJ hybrids. However, the DJ OIHP bulk single crystal constructed by using the advantages of FA as perovskitizers and aromatic diamines as spacers is still blank. Herein, we integrate the properties of organic cations and inorganic skeletons at a molecular-scale to construct a broadband-responsive 2D bilayer DJ perovskite (3AMPY)(FA)Pb₂I₇ [3AMPY = 3-(aminomethyl)pyridinium], which shows a fascinating detectivity from X-ray (5.23 × 10⁴ μC Gy_air^-1 cm^-2 at 200 V bias) and visible light (6 × 10¹² jones at 637 nm) to the near-infrared region (2.6 × 10⁹ jones at 780 nm). After an in-depth analysis of structure and optical properties, we found that the distortion degree of Pb-I-Pb bond angles between adjacent PbI₆ octahedra plays a crucial role on optical properties; on the other hand, the interlayer spacer cations (3AMPY) and intralayer perovskitizers (FA) mutual participate in the contribution of the conduction band, making (3AMPY)(FA)Pb₂I₇ have a narrow optical band gap of 1.54 eV. Such a 2D perovskite material with a wide spectra response will be the preferred choice for photodetection under complex conditions.

A lead-free halide hybrid perovskite (TMHD)BiCl5 for ultraviolet photodetection

Lead halide hybrid perovskites with a wide bandgap (e.g., CH3NH3PbCl3) have gained tremendous attention in the field of ultraviolet (UV) photodetection due to their brilliant optoelectronic activity.

A lead-free layered Dion–Jacobson hybrid double perovskite constructed by an aromatic diammonium cation

A two-dimensional Dion–Jacobson type lead-free hybrid double perovskite [(3AMPY)₂AgBiI₈·H₂O] (3AMPY = 3-(aminomethyl) pyridinium) constructed by an aromatic diammonium cation exhibits an attractive narrow band gap (E_g = 1.86 eV).

Unique cation-template three-dimensional hybrid material demonstrates dielectric switchable response

The strict tolerance space of three-dimensional (3D) crystalline structures is still a significant challenge in the area of switching dielectrics in comparison with lower-dimensional structures. Generally, the function of crystalline materials can be given or adjusted by controlling the environment in which synthesis takes place or the packing rearrangement. Using this method, special functional enhancements or changes in the dielectrics can be realized by improving the synthetic strategies. Here, a 3D switchable dielectric compound [MeHdabco]K(BF4)3 was achieved by employing the temperature selective effect. In particular, its structure is completely different from the usual 3D perovskite structure, which is constructed using two different cation-template frameworks. Moreover, the 3D [MeHdabco]K(BF4)3 shows a structural phase transition at 358 K. The thermal analysis (differential scanning calorimetry (DSC)) and X-ray diffractometry results provided evidence of these phase changes. This work provides a feasible strategy that can be used to achieve the different structures of an 'isomer', and enrich the method used for designing diverse functional materials.