Highly Efficient Self-Trapped Exciton Emission of a (MA)4Cu2Br6 Single Crystal.

Recently, low-dimensional organic-inorganic lead halide perovskites have attracted a great deal of attention due to their outstanding tunable broadband emission, while the toxicity of lead hinders their further application in the photoelectric field. Here, we report a novel lead-free Cu(I)-based organic-inorganic perovskite-related material of a (MA)4Cu2Br6 single crystal with zero-dimensional clusters, which is a unique Cu2Br64- corner-sharing tetrahedron dimer structure consisting of two connected tetrahedra. The single crystal displays a bright broadband green emission with a high photoluminescence with a quantum yield of ≤93%, a large Stokes shift, and a very long (microsecond) photoluminescence (PL) lifetime, resulting from self-trapped exciton emission. The direct band gap characteristic of (MA)4Cu2Br6 was proven by density functional theory calculation, and its band gap was determined by experiments to be ∼3.87 eV. In the temperature range of 98-258 K, the PL intensity increases gradually with an increase in temperature due to the deep trapping out of strong electro-phonon coupling, while the PL decreases when the temperature increases over 258 K due to phonon scattering. It is worth mentioning that this new material has high chemical and light stability, in contrast to the lead perovskite.

Interlayer of PMMA Doped with Au Nanoparticles for High-Performance Tandem Photodetectors: A Solution to Suppress Dark Current and Maintain High Photocurrent.

Currently, colloidal quantum dots (CQDs)-based photodetectors are widely investigated due to their low cost and easy integration with optoelectronic devices. The requirements for a high-performance photodetector are a low dark current and a high photocurrent. Normally, photodetectors with a low dark current also possess a low photocurrent, or photodetectors with reduced dark current possess a reduced photocurrent, resulting in low detectivity. In this paper, a solution to suppress dark current and maintain a high photocurrent, i.e., use of poly(methyl methacrylate) doped with Au nanoparticles (NPs) (i.e., PMMA:Au) as an interlayer for enhanced-performance tandem photodetectors, is presented. Our experimental data showed that the dark current through the tandem photodetector ITO/PEDOT:PSS/PbS:CsSnBr3/ZnO/PMMA:Au/CuSeN/PbS:CsSnBr3/ZnO/Ag is suppressed significantly; meanwhile, a high photocurrent is maintained after a PMMA:Au interlayer has been inserted between two subdetectors. The inserted PMMA:Au interlayer acts as storage nodes for electrons, reducing the dark current through the device; meanwhile, the photocurrent can be enhanced under illumination. As a result, the specific detectivity of the tandem photodetector with 35 nm PMMA:Au interlayer was enhanced significantly from 5.01 × 1012 to 2.7 × 1015 Jones under 300 µW/cm2 532 nm illumination at a low voltage of -1 V as compared to the device without a PMMA:Au interlayer. Further, the physical mechanism of enhanced performance is discussed in detail.

Self-powered, all-solution processed, trilayer heterojunction perovskite-based photodetectors.

Heterostructures composed of nano-/micro-junctions, combining the excellent photon harvesting properties of nano-systems and the ultrafast carrier transfer of micro-systems, have a promising role in high-performance photodetectors. In this paper, a highly-sensitive trilayer self-powered perovskite-based photodetector ITO/ZnO (70 nm)/CdS (150 nm)/CsPbBr3 (200 nm)/Au, in which the CdS nanorods (NRs) layer is sandwiched between a ZnO/CsPbBr3 interface to reduce the interfacial charge carriers' recombination and the charge transport resistance, is presented. Due to the strong built-in potential and the internal driving electric-field, an ultra-high On/Off current ratio of 106 with a responsivity of 86 mA W-1 and a specific detectivity of 6.2 × 1011 Jones was obtained at zero bias under 85 µW cm-2 405 nm illumination and its rise/decay time at zero bias is 0.3/0.25 s. Therefore, the enhanced device performance strongly suggests the great potential of such a trilayer heterojunction device for use in high-performance perovskite photodetectors.

All-solution-processed UV-IR broadband trilayer photodetectors with CsPbBr3 colloidal nanocrystals as carriers-extracting layer.

Colloidal quantum dots (CQDs) are very promising nanomaterials for optoelectronics due to their tunable bandgap and quantum confinement effect. All-inorganic CsPbX3 (X = Br, Cl and I) perovskite nanocrystals (NCs) have attracted enormous interests owing to their promising and exciting applications in photovoltaic devices. In this paper, all-solution-processed UV-IR broadband trilayer photodetectors ITO/ZnO/PbS/CsPbBr3/Au and ITO/ZnO/CsPbBr3/PbS/Au with high performance were presented. The role of CsPbBr3 QDs layer as the carriers-extracting layer in the trilayer devices was discussed. As compared with bilayer device ITO/ZnO/PbS/Au, both the dark currents and photocurrents under illumination from trilayer photodetectors are enhanced, but the trilayer photodetector ITO/ZnO(80 nm)/PbS(150 nm)/CsPbBr3(50 nm)/Au showed a maximum specific detectivity (D*) of 8.3 × 1012 Jones with a responsivity (R) of 35 A W-1 under 1.6 mW cm-2 980 nm illumination. However, another trilayer photodetector ITO/ZnO(80 nm)/CsPbBr3(50 nm)/PbS(150 nm)/Au showed a maximum D* of 1.73 × 1012 Jones with a R of 5.31 A W-1 under 6.8 mW cm-2 405 nm illumination. Further, the underlying mechanism for the enhanced performance of trilayer photodetectors was discussed. Thus, this strategy of all-solution-processed heterojunction configuration paves a facile way for broadband photodetectors with high performance.