Pure-red perovskite LEDs (PeLEDs) based on CsPb(Br/I) 3 nanocrystals (NCs) usually suffer from a compromise in emission efficiency and spectral stability on account of the surface halide vacancies-induced nonradiative recombination loss, halide phase segregation, and self-doping effect. Herein, a “halide-equivalent” anion of benzenesulfonate (BS – ) is introduced into CsPb(Br/I) 3 NCs as multifunctional additive to simultaneously address the above challenging issues. Joint experiment-theory characterizations reveal that the BS – can not only passivate the uncoordinated Pb 2+ -related defects at the surface of NCs, but also increase the formation energy of halide vacancies. Moreover, because of the strong electron-withdrawing property of sulfonate group, electrons are expected to transfer from the CsPb(Br/I) 3 NC to BS – for reducing the self-doping effect and altering the n-type behavior of CsPb(Br/I) 3 NCs to near ambipolarity. Eventually, synergistic boost in device performance is achieved for pure-red PeLEDs with CIE coordinates of (0.70, 0.30) and a champion external quantum efficiency of 23.5%, which is one of the best value among the ever-reported red PeLEDs approaching to the Rec. 2020 red primary color. Moreover, the BS – -modified PeLED exhibits negligible wavelength shift under different operating voltages. This strategy paves an efficient way for improving the efficiency and stability of pure-red PeLEDs.
Xiaodong Zhang,Bohui Xu,Deshuai Xiao,Xinyuan Zhang,Pifu Gong,Zheshuai Lin
Ultraviolet (UV) nonlinear optical (NLO) materials are critical for laser frequency conversion to extend wavelength ranges. Sulfates have emerged as a promising family of UV NLO materials, yet their NLO performance is constrained by the low optical anisotropy of the constituent [SO4]2− groups. In this study, we investigate the [C6H5SO3]− group, formed by substituting a ligand of the non-π-conjugated [SO4]2− unit with a π-conjugated benzene ring, and demonstrate that this group has a strong second harmonic generation (SHG) response and large birefringence. Leveraging this optimized structural unit, we successfully synthesize the first UV NLO benzenesulfonate, Y(C6H5SO3)3·9H2O. This compound exhibits enhanced UV optical properties, including a short cutoff edge of 280 nm, a relatively large SHG efficiency (0.8 × KDP), and a large birefringence of 0.16 at 1064 nm. This work not only presents Y(C6H5SO3)3·9H2O as a competitive UV NLO material, but also highlights the [C6H5SO3]− group as a highly effective structural motif for the future development of advanced UV NLO materials.
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