Reducing Amplified Spontaneous Emission Threshold in CsPbBr3 Quantum Dot Films by Controlling TiO2 Compact Layer

Abstract

Amplified spontaneous emission (ASE) threshold in CsPbBr3 quantum dot films is systematically reduced by introducing high quality TiO2 compact layer grown by atomic-layer deposition. Uniform and pinhole-free TiO2 films of thickness 10, 20 and 50 nm are used as a substrates for CsPbBr3 quantum dot films to enhance amplified spontaneous emission performance. The reduction is attributed indirectly to the improved morphology of TiO2 compact layer and subsequently CsPbBr3 active layer as grown on better quality substrates. This is quantified by the reduced roughness of the obtained films to less than 5 nm with 50 nm TiO2 substrate. Considering the used growth method for the quantum dot film, the improved substrate morphology maintains better the structure of the used quantum dots in the precursor solution. This results in better absorption and hence lower threshold of ASE. Besides that, the improved film quality results further in reducing light scattering and hence additional slight optical enhancement. The work demonstrates a potential venue to reduce the amplified spontaneous emission threshold of quantum dot films and therefore enhanced their optical performance.

Enhancement of Light Amplification of CsPbBr3 Perovskite Quantum Dot Films via Surface Encapsulation by PMMA Polymer

“…01-075-0412), with slight peak shifts. Slight shifts in peak positions (~0.6 • ) were consistent with alloy formation and the results are well in line with previous reports [31]. The peak shifts decrease when the top surface of the PQD was modified by the PMMA polymer; they revert to appear as in the bare surface of PQD when the PQD top and bottom surface are modified.…”

“…Figures 4 and 5a show the UV-vis absorption and steady-state photoluminescence (PL) spectra of the bare perovskite film and that modified by PMMA polymer in one and two faces. These results correspond well to perovskite film results reported for CsPbBr3 films, with only a change in intensity [30,31]. Additionally, the high crystallinity of the perovskite film was confirmed by the observation of narrow-band emission (FWHM) located at 516 nm, which indicates a low density of defect states as shown in XRD results.…”

“…The ASE thresholds of CsPbBr 3 thin films were demonstrated under picosecond laser excitation around 22.5 µJ cm −2 , which confirmed the role of laser pulse duration in determined the ASE threshold [30]. In one of the previously published works, the ASE threshold in CsPbBr 3 quantum dot films was reducing through controlling the TiO 2 compact layer under perovskite film by the reduced roughness of the obtained films to less than 5 nm with 50 nm TiO 2 substrate [31].…”

Single-Source Thermal Evaporation Growth and the Tuning Surface Passivation Layer Thickness Effect in Enhanced Amplified Spontaneous Emission Properties of CsPb(Br0.5Cl0.5)3 Perovskite Films

“…Thus, ASE provides an applicable benchmark for determining the material suitability for gain applications. The coherence degree of the laser is much higher than that of ASE, even though the ASE may be much more intense [ 28 , 57 ].…”

“…Additionally, surface passivation can involve encapsulation by organic polymer matrices (e.g., polymethyl methacrylate (PMMA) [ 13 , 14 ], polyvinylidene fluoride, ethylene vinyl acetate, or anthracene [ 15 , 16 , 17 ]). Furthermore, the surface passivation process can involve encapsulation by some mesoporous inorganic dielectric materials by embedding PQDs into mesoporous particles via a facile mixing method (e.g., SiO 2 [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ], TiO 2 [ 25 , 26 , 27 , 28 ], or glass sheets [ 29 ]). The polymer films should be compatible with perovskite films under appropriate processing conditions, and encapsulation materials should be transparent to ensure that the optical properties are preserved [ 30 , 31 ].…”