| 1. |
- Liu, Yong-feng, et al.
(författare)
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Highly Soluble CsPbBr3 Perovskite Quantum Dots for Solution-Processed Light-Emission Devices
- 2021
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Ingår i: ACS Applied Nano Materials. - : American Chemical Society (ACS). - 2574-0970. ; , s. 1162-1174
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Tidskriftsartikel (refereegranskat)abstract
- We report on the synthesis of CsPbBr3 perovskite quantum dots (PeQDs) with a high solubility of 75 g/L in toluene and a good film-forming property, as enabled by a dense layer of didodecyldimethylammonium bromide and octanoic acid surface ligands. The crystalline and monodisperse PeQDs feature a cubic-like shape, with an edge length of 10.1 nm, and a high photoluminescence quantum yield of greater than 90% in toluene solution and 36% as a thin film. We find that the PeQDs are n-type doped following the synthesis but also that they can be p-type and additionally n-type doped by in situ electrochemistry. These combined properties render the PeQDs interesting for the emitter in solution-processed light-emitting electrochemical cells (LECs), and we report a PeQD-LEC with air-stabile electrodes that emits with a narrow emission spectrum (λpeak = 514 nm, full width at half-maximum = 24 nm) and a luminance of 250 cd/m2 at 4 V and a luminance of 1090 cd/m2 at 6.8 V. To reach this performance, it was critical to include a thin solution-processed layer comprising p-type poly(vinyl carbazole) and a tetrahexylammonium tetrafluoroborate ionic liquid between the PeQD emission layer and the anode in order to compensate for the as-synthesized n-type doping of the PeQDs.
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| 2. |
- Yang, Jinpeng, et al.
(författare)
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Accessing the Conduction Band Dispersion in CH3NH3PbI3 Single Crystals
- 2021
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Ingår i: The Journal of Physical Chemistry Letters. - : AMER CHEMICAL SOC. - 1948-7185. ; 12:15, s. 3773-3778
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Tidskriftsartikel (refereegranskat)abstract
- The conduction band dispersion in methylammonium lead iodide (CH3NH3PbI3) was studied by both angle-resolved two-photon photoelectron spectroscopy (AR-2PPE) with low photon intensity (similar to 0.0125 nJ/pulse) and angle-resolved low-energy inverse photoelectron spectroscopy (AR-LEIPS). Clear energy dispersion of the conduction band along the Gamma-M direction was first observed by these independent methods under different temperatures, and the dispersion was found to be consistent with band calculation under the cubic phase. The effective mass of the electrons at the Gamma point was estimated to be (0.20 +/- 0.05)m(0) at the temperature of 90 K. The observed conduction band energy was different between the AR-LEIPS and AR-2PPE, which was ascribed to the electronic-correlation-dependent difference of initial and final states probing processes. The present results also indicate that the surface structure in CH3NH3PbI3 provides the cubic-dominated electronic property even at lower temperatures.
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| 3. |
- Yang, Jinpeng, et al.
(författare)
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Temperature-dependent band structure evolution determined by surface geometry in organic halide perovskite single crystals
- 2020
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Ingår i: Physical Review B. - : AMER PHYSICAL SOC. - 2469-9950 .- 2469-9969. ; 102:24
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Tidskriftsartikel (refereegranskat)abstract
- Organic halide perovskites have attracted much attention due to their potential applications in optoelectronic devices. Since the generally higher flexibility compared to their inorganic counterparts, their structures are prone to be more sensitive toward external effects, where the fundamental understanding of their band structure evolutions is still inconclusive. In this study, different electronic structure evolutions of perovskite single crystals are found via angle-resolved photoelectron spectroscopy: (i) Unchanged top valence band (VB) dispersions under different temperatures can be found in the CH3NH3PbI3. (ii) Phase transitions induced the evolution of top VB dispersions, and even a top VB splitting with Rashba effects can be observed in the CH3NH3PbBr3. Combined with low-energy electron diffraction, metastable atom electron spectroscopy, and density functional theory calculation, we confirm that different band structure evolutions observed in these two perovskite single crystals originated from the cleaved top surface layers, where the different surface geometries with CH3NH3+-I in CH3NH3PbI3 and Pb-Br in CH3NH3PbBr3 are responsible for finding band dispersion change and appearance of the Rashba-type splitting. Such findings suggest that the top surface layer in organic halide perovskites should be carefully considered to create functional interfaces for developing perovskite devices.
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