Deep‐red light‐emitting diodes (DR‐LEDs, >660 nm) with high color‐purity and narrow‐bandwidth emission are promising for full‐color displays and solid‐state lighting applications. Currently, the DR‐LEDs are mainly based on conventional emitters such as organic materials and heavy‐metal based quantum dots (QDs) and perovskites. However, the organic materials always suffer from the complicated synthesis, inferior color purity with full‐width at half‐maximum (FWHM) more than 40 nm, and the QDs and perovskites still suffer from serious problems related to toxicity. Herein, this work reports the synthesis of efficient and high color‐purity deep‐red carbon dots (CDs) with a record narrow FWHM of 21 nm and a high quantum yield of more than 50% from readily available green plants. Moreover, an exciplex host is further established using a polymer and small molecular blend, which has been shown to be an efficient strategy for producing high color‐purity monochrome emission from deep‐red CDs via Förster energy transfer (FET). The deep‐red CD‐LEDs display high color‐purity with Commission Internationale de l'Eclairage (CIE) coordinates of (0.692, 0.307). To the best of the knowledge, this is the first report of high color‐purity CD‐LEDs in the deep‐red region, opening the door for the application of CDs in the development of high‐resolution light‐emitting display technologies.
Elaborate engineering of emitting wavelength of green down‐converter in the spectral range of ≈525–535 nm with narrow full‐width at half‐maximum (fwhm < 25 nm) is an essential prerequisite for faithfully reproducing colors in the quantum dot (QD)‐based backlit display. Herein, different from the previous complex synthesis for green films, FAPbBr3 perovskite QDs films are fabricated by a dual‐additive assisted in situ growth strategy. Both C6H5CH2CH2NH3+ and 1,4,7,10,13,16‐hexaoxacyclooctadecane additives are introduced to synergistically tune green emitting (≈525–535 nm) with the narrowest fwhm down to 21 nm and the highest photoluminescence quantum yield (PLQY) up to 99%. Improved nanocomposite film with excellent long‐term stability is used to construct a prototype liquid crystal display (LCD) with a wide color gamut (118% National Television System Committee and 88% Recommendation BT 2020), a high saturation, and a remarkable color rendition. The performance is superior to that of the commercial white‐LED‐based LCD, showing a great potential of the present green film for high‐definition display application in the future.
High-performance 86 μJ, 11.2 fs pulses with a spectrum range of 800-1050 nm are generated based on 1030 nm, 190 fs Yb femtosecond pulses by using multi-plate based spectral broadening and filtering. Taking advantage of single beam configuration, the obtained pulses own excellent power and spectral stabilities. Since the output spectrum is obtained by spectrally filtering the broadened components, the temporal contrast of output pulses is enhanced by at least four orders of magnitude. Together with the robust and simple setup, the proposed method is expected to be a competitive option for the generation of seed pulses for 10s-100s petawatt lasers.
To achieve multi-petawatt pulses, the generation of high-temporal-contrast few-cycle seed pulses with the central wavelength of 910 nm is the first step. In this research, high-performance seed pulses with a spectrum ranging from 800 nm to 1050 nm and pulse energy of 86 μJ are generated based on the filtered multi-plate spectral broadening and spectral filtering from a Yb-based femtosecond laser system. With self-phase modulation (SPM) induced spectral broadening, the input with relatively narrow spectrum bandwidth is broadened widely, which enables the final output pulse be compressed from full width at half maximum (FWHM) of 190 fs to 11.2 fs and a compression ratio of about 18 after dispersion compensation. The experiments show that the temporal contrast of the final output pulse is improved by at least four orders of magnitude through spectral filtering and new spectral components generated by third-order nonlinear processes such as SPM and self-focusing. Furthermore, taking advantage of single beam and self-focusing process, the final output has high energy stability and spectrum stability. Based on the merits above, together with its simplicity and robustness, this method proposed is expected to be used for the seed pulse generation of 10s-100s petawatt (PW) level laser system in the future.
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