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Organic small-molecule luminescent materials have high fluorescence quantum efficiency, are easy to purify, and show advantages related to brightness. However, the low mobility of hole carriers hinders their practical applications. To obtain luminescent materials with high fluorescence quantum efficiency, we investigated organic small-molecule thiophene oligomers with electron-donating or electron-accepting substituents at the terminal groups using the density functional theory. Compared with the electron-donating groups (–NH2, –CH3, –C2H5, and –C3H7), the electron-withdrawing groups (–NO2 and –COOH) resulted in unusual electronic and photoluminescent properties. The ultraviolet spectra of the thiophene oligomer derivatives could be modulated in the range of 200–500 nm, making them suitable for application in organic light-emitting devices. In particular, the group with the strongest electron-withdrawing effect (–NO2) resulted in blue light emission in the wavelength range of 400–480 nm, suitable for application in blue chips. Finally, the calculation results show that the donor–acceptor-modified oligomers are worthy of synthesis due to their relatively high electron mobilities. [ABSTRACT FROM AUTHOR]

Recently, Kovalenko and co-workers and Li and co-workers developed CsPbX3 (X = Cl, Br, I) inorganic perovskite quantum dots (IPQDs), which exhibited ultrahigh photoluminescence (PL) quantum yields (QYs), low-threshold lasing, and multicolor electroluminescence. However, the usual synthesis needs high temperature, inert gas protection, and localized injection operation, which are severely against applications. Moreover, the so unexpectedly high QYs are very confusing. Here, for the first time, the IPQDs' room-temperature (RT) synthesis, superior PL, underlying origins and potentials in lighting and displays are reported. The synthesis is designed according to supersaturated recrystallization (SR), which is operated at RT, within few seconds, free from inert gas and injection operation. Although formed at RT, IPQDs' PLs have QYs of 80%, 95%, 70%, and FWHMs of 35, 20, and 18 nm for red, green, and blue emissions. As to the origins, the observed 40 meV exciton binding energy, halogen self-passivation effect, and CsPbX3@X quantum-well band alignment are proposed to guarantee the excitons generation and high-rate radiative recombination at RT. Moreover, such superior optical merits endow them with promising potentials in lighting and displays, which are primarily demonstrated by the white light-emitting diodes with tunable color temperature and wide color gamut. [ABSTRACT FROM AUTHOR]

All-inorganic cesium lead halide perovskites have been emerging as the promising semiconductor materials for next-generation optoelectronics. However, the fundamental question of how the environmental atmosphere affects their photophysical properties, which is closely related to the practical applications, remains elusive. Here, we report the dynamic switching between radiative exciton recombination and non-radiative carrier trapping in CsPbBr3 by controlling the atmospheric conditions. Specifically, we show that the photoluminescence (PL) intensity from the CsPbBr3 crystals can be boosted by ~ 60 times by changing the surrounding from vacuum to air. Based on the comprehensive optical characterization, near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) as well as density functional theory (DFT) calculations, we unravel that the physisorption of oxygen molecules, which repairs the trap states by passivating the PL-quenching bromine vacancies, is accountable for the enhanced PL in air. These results are helpful for better understanding the optical properties of all-inorganic perovskites. Perovskite-based optoelectronics are expected to become an important component of devices such as solar cells and light-emitting diodes. However, how they are affected by environmental conditions is still not fully understood. The authors investigate the mechanisms, which occur for inorganic perovskites when in contact with ambient atmosphere and how this could potentially impact upon device performance. [ABSTRACT FROM AUTHOR]

A room‐temperature supersaturated recrystallization method is developed on page 2435 by H. Zeng and co‐workers, to rapidly synthesize all‐inorganic halide perovskite quantum dots with blue, green, and red luminescent quantum yields of 70–95% and line‐widths less than 35 nm. The origins of the optical superiority are proposed to be the 40 meV exciton binding energy, surface self‐passivation, and quantum‐well band alignment, leading to promising potential in healthy lighting and wide‐color‐gamut displays. [ABSTRACT FROM AUTHOR]