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Bimetallic oxides have been considered as potential candidates for supercapacitors due to their relatively high electric conductivity, abundant redox reactions and cheapness. However, nanoparticle aggregation and huge volume variation during charging-discharging procedures make it hard for them to be applied widely. In this work, one-dimensional (1D) MnFe2O4@C nanowires were in-situ synthesized via a simply modified micro-emulsion technique, followed by thermal treatment. The novel 1D and core-shell architecture, and in-situ carbon coating promote its electric conductivity and porous feature. Due to these advantages, the MnFe2O4@C electrode exhibits a high specific capacitance of 824 F·g−1 at 0.1 A·g−1 and remains 476 F·g−1 at 5 A·g−1. After 10,000 cycles, the capacitance retention of the MnFe2O4@C electrode is up to 93.9%, suggesting its excellent long-term cycling stability. After assembling with activated carbon (AC) to form a MnFe2O4@C//AC device, the energy density of this MnFe2O4@C//AC device is 27 W·h·kg−1 at a power density of 290 W·kg−1, and remains at a 10 W·h·kg−1 energy density at a high power density of 9300 W·kg−1.

photoluminescence quantum yield, large exciton binding energy, high optical gain coefficients, and bandgap tunability. [5][6][7][8][9][10][11] Especially, the tailorable emission wavelength of perovskites is highly appealing for overcoming the so-called green gap problem in nitride-based LEDs and lasers. Since the first demonstration of amplified spontaneous emission (ASE) phenomenon of perovskites at room temperature in 2014, [5] lasering behavior has been extensively investigated for perovskite-based gain mediums combined with various optical feedback structures. [12][13][14] However, the key challenge in the practical application of 3D-perovskite is the well-known long-term instability of devices owing to atmospheric moisture and halide ion migration. [15] Recently, the solution-processed quasi-2DRuddlesden-Popper perovskites (RPPs) have been investigated as attractive alternatives to 3D-perovskites for laser applications because of their inherent stability. [16][17][18][19] The quasi-2D RPPs can be described by the chemical formula L 2 A n−1 Pb n X 3n+1 , where L represents large organic spacers such as phenylethylammonium (PEA), n-butylammonium (BA), and naphthylmethylammonium (NMA), A is a small organic cation of methylammonium (MA + ), formamidinium (FA + ), or inorganic cation of Cs + , X is a halide anion (Cl − , Br − , I − ), and n represents the number of PbX 6 octahedral layers within each period. [16] Actually, both ASE [20][21][22][23] and lasing behaviors have been widely demonstrated in the quasi-2D RPP films with whispering-gallery-mode, [24,25] Fabry-Pérot, [26,27] distributed feedback (DFB) [18,28,29] and distributed Bragg reflector [30] cavities at room temperatures. The hydrophobic bulky organic layers of cation L can suppress ion migration and prevent moisture penetration, thus imparting quasi-2D perovskites with excellent environmental and operating stability. [31][32][33][34] Indeed, it was reported that the ASE intensity maintained almost the same after excitation under continuous pulsed laser for 32 h at ambient conditions. [20] More importantly, because of dielectric constant difference between RPPs and organic layers, the excitons are confined within the [A n−1 Pb n X 3n+1 ] 2− layers, resulting in a large exciton binding energy up to hundreds of meV. [35] Furthermore, the quasi-2D RPP thin films typically consist of the mixed 2D/3D perovskite phases, naturally forming multi-quantum-well structures. Consequently, the photoexcited Solution-processed quasi-2D Ruddlesden-Popper perovskites are being considered as a promising optical gain medium in lasing applications, owing to their outstanding optoelectronic properties and inherent stability. However, the development of quasi-2D perovskites for lasers with low threshold and high optical gain is still lagging far behind 3D-perovskites. This work proposes an anti-solvent treatment strategy to regulate the phase components and surface morphology of quasi-2D PEA 2 (CsPbBr 3 ) n−1 PbBr 4 thin films. Furthermore, an additional poly(methyl meth...

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