Mn-doped Perovskite Nanocrystals Research Articles

Paper-Thin Al-Catalyzed Si Nanowire Solar Cells and Efficiency Enhancement by Hybrid Nanostructures with Mn-Doped Perovskite Nanocrystals

The use of thin silicon (Si) wafers and streamlined fabrication methods that can be scaled up without compromising device efficiency is a key strategy for realizing low-cost and flexible solar cells. Herein, aluminum (Al)-catalyzed Si nanowires (NWs) formed by vapor–liquid–solid growth on paper-thin polished and etched Si(111) wafers of 100 and 60 μm thickness with high proficiency for minimizing interfacial defects and light absorption loss have been accomplished. Successfully addressing the major challenge of rapid Al catalyst oxidation by ex situ and uncomplicated growth conditions allows for the potential to scale up the process while preventing the formation of deep-level traps resulting from catalyst contamination. The Si NWs formed on the nanowave surface of a thin etched Si wafer evidence comparable light absorbance and low interfacial defects to those grown on thin polished and traditional Si wafers. Fabrication of thin Si NW solar cells with a homojunction p+–p–n–n+ structure toward the enhanced power conversion efficiency (PCE) by hybrid nanostructures with manganese-doped cesium lead chloride (CsPb0.81Mn0.19Cl3) perovskite nanocrystals (NCs) using a simple drop-casting method has been explicitly explained. The precise tuning of the energy band and NC size enabled a significant radiative energy transfer by matching the light absorption range of NCs with a high Stokes shift in the luminescence spectrum and the spectral response range of underlying Si solar cells. The nonradiative energy transfer efficiency of NCs and an NC amount infiltration on homojunction Si NW solar cells for maximizing PCE enhancement were examined. The effective photon-harvesting architectures of NWs and NCs together with efficient energy transfers and surface passivation from NCs to the underlying homojunction Si NW solar cells could capably enhance PCE up to a 9% level. These results exhibited the potential for feasible low-cost and large-scale fabrication techniques with lower consumption of raw materials for future photovoltaic applications.

Effect of Electronic Structure on Delayed Fluorescence in Mn-Doped Perovskite Nanocrystals

Effect of Electronic Structure on Delayed Fluorescence in Mn-Doped Perovskite Nanocrystals

A-Site FA+ Doping-Enhanced Photoluminescence Efficiency and Photostability of Mn-Doped Perovskite Nanocrystals

Improving the optical and structural stability of highly luminescent Mn2+-doped CsPbCl3–yBry (Mn:CsPbCl3–yBry) nanocrystals (NCs) under ultraviolet illumination is very necessary for their application in solid-state lighting. Herein, greatly improved photoluminescence (PL) quantum yield (QY) and illumination stability were observed in Mn:CsPbCl3 NCs by incorporation of an appropriate FA+ amount into the crystal lattice. The Mn:FAxCs1–xPbCl3 NCs showed higher PL QYs (up to 76%), longer Mn2+ PL lifetimes, and nearly single-exponential decay relative to the Mn:CsPbCl3 ones. With the increase in irradiation time, a slowly reduced PL intensity and an almost unchanged PL peak position and linewidth of Mn2+ ions in Mn:FA0.15Cs0.85PbCl3 NCs were found, suggesting that the mixing of FA+ and Cs+ can increase the tolerance of the lattice and improve the photostability of the NCs. Under high-power ultraviolet irradiation, the light-induced Mn2+ PL attenuation of Mn:FA0.15Cs0.85PbCl3 NCs was slower than that of the ones without FA+, and no divisive emission peaks representing Br-rich and Cl-rich regions appeared in Mn:FA0.15Cs0.85PbCl3–yBry NCs, which was consistent with the result that the X-ray diffraction peaks of the NCs with FA+ remained constant with irradiation time. This indicates that severe Mn2+ ion diffusion and halogen ion segregation can be effectively inhibited by adding FA+ into the Mn-doped perovskite NCs.

In situ preparation of Mn-doped perovskite nanocrystalline films and application to white light emitting devices

Mn-doped perovskite nanocrystals have promised new optoelectronic applications due to their unique material properties. In the present study, Mn-doped perovskite nanocrystalline films were prepared in situ in a polymer matrix. The Mn-doped perovskite nanocrystals (PNCs) had good crystallinity and uniform size/spatial distributions in the polymer film. Bright dual-color emission and the long lifetime of the excited state of the dopant were observed from the host exciton and the Mn2+ dopant, respectively. Furthermore, magnetism was observed in the optimal Mn2+ concentration, implying that magnetic coupling was achieved in the Mn-doped perovskite lattice. The Mn-doped perovskite films also showed superior stability against moisture. To demonstrate the practicality of this composite film, a white light emitting device was fabricated by combining a single composite film with a blue light emitting diode; the device showed a high-quality white light emission, and the Commission Internationale De L'Eclairage (CIE) chromaticity coordinate of the white light emitting diode (WLED) (0.361, 0.326) was close to the optimal white color index. In this single-layer WLED, self-absorption among the luminous multilayers in traditional white light emitting diodes can be avoided. The study findings revealed that Mn-doped perovskite nanocrystalline films have many exciting properties, which bodes well for the fundamental study and design of high-performance optoelectronic devices.

Influence of PMMA thin film combined with Mn-doped cesium lead halide perovskite CsPbCl3

To improve the stability and enable luminescent devices, especially in moisture and oxygen atmosphere, Cesium lead Halide perovskite nanocrystals (PNCs) are usually encapsulated by polymer host matrices as the highly effective emission center. However, simple PNCs are facing matrix absorption and reabsorption of PNCs in bulk structure or film structures. To solve these problems, we introduced a thin film structure made of Polymethylemthacrylate (PMMA) that incorporated into Mn-doped CsPbCl3 PNCs on silica substrate. The enlargement in Stocks shift (about 200 nm) of PNCs has effectively reduced the reabsorption between different PNCs. Two types of PNCs nanostructure (nanocube and nanoplatelet) were prepared. To figure out the influence of PNCs nanostructure and PMMA ratio, series of samples were prepared and compared on their optical performance including photoluminescence (PL) intensity spectra, photoluminescence excitation (PLE) spectra, absorption spectra and temperature dependent PL spectra. Such a thin PMMA film with Mn-doped PNCs has great stability on emission wavelength during the change of PMMA ratio and temperature, which is promising for the uses in potential application such as luminescent solar concentration on glass window.

Enhanced luminescence of Mn doped CsPbCl3 and CsPb(Cl/Br)3 perovskite nanocrystals stabilized in glasses

Introducing of impurity ions into semiconductor nanocrystals can improve their photoluminescence quantum efficiency through energy transfer and enhance their applicability towards light-emitting devices. In this work, Mn doped CsPbCl3 and CsPbCl3-xBrx perovskite nanocrystals were prepared in glass through melt-quenching and subsequent thermal treatment. Both Mn doping concentration and thermal treatment conditions affected the growth and resultant band edge emission of perovskite nanocrystals, enabling tunable photoluminescence ranging from UV to blue. In addition to UV-blue band edge emission from these Mn-doped perovskite nanocrystals, red emission from Mn ions was activated through efficient energy transfer from perovskite nanocrystals. Intensity ratio between the band edge emission of perovskite nanocrystals and red emission of Mn ions was also tunable by varying the Mn doping concentration and heat-treatment conditions, covering a wider color gamut. Along with the good chemical and mechanical properties of glass matrix, these Mn-doped cesium lead halide perovskite nanocrystal embedded glasses have potentials for applications in light emitting devices.

Efficient recycling of trapped energies for dual-emission in Mn-doped perovskite nanocrystals

Doping impurity into semiconductor nanocrystals (NCs) is able to create novel optical, electronic, and magnetic functionalities. Recently, dual-emissions from Mn-doped lead chloride perovskites NCs have attracted much attention. However, the mechanisms of doping and energy-transfer to Mn ions of the perovskite NCs are still unclear. In this work, through the newly-developed post-treatment methods, it is found that excess Cl- can boost the Mn-emission due to the efficient ion diffusion and exchanges during Mn-doping processes. Importantly, a clear slow energy accumulation in the Mn dopants with time constant of ~ 200 ns is revealed from time-resolved photoluminescence (PL) measurements. Together with the doping insensitive band edge PL, these results indicate that the Mn dopants should snatch the energy from non-radiative trap states rather than from band states, which implies an efficient recycling of trapped nonradiative energy for luminescence by the dopants. The developed efficient doping method and proposed mechanism of energy transfer would provide unique insights into the mechanisms of doping. Moreover, fundamental investigations on nanostructure and optical properties are expected to increase its potential in electronic or magnetic applications.