Colloidal semiconductor nanoparticles have a great potential for designing high-quality white-light-emitting diodes (WLEDs). However, the nanoparticles suffer from the reabsorption effect due to the characteristic small Stokes-shifts, which limits the power conversion efficiency of the light sources. In order to resolve this problem, absorption and emission spectra of the nanoparticles should be separated. Here, we report on gradient alloy CdSe_1–xS_x nanoplatelets (NPLs), which allow for suppression of the reabsorption. Thanks to the gradient composition, the S-rich domains of CdSe_1–xS_x NPLs behave as an efficient antenna, adsorbing light and funneling the generated carriers into the Se-rich domains, where they recombine. The gradient structure of CdSe_1–xS_x NPLs allows one to control the overlap of the emission and absorption spectra simply by varying their composition. By controlling the composition of CdSe_1–xS_x NPLs, their photometric parameters, including chromaticity color coordinates, color rendering index (CRI), and correlated color temperature (CCT), can be tuned. Due to the wide trap-assisted emissions associated with unsaturated S/Se surface atoms, CdSe_1–xS_x NPLs demonstrate exceptionally high CRI values ranging from 87 up to 94 at CCT values in the range of 2509–6448 K, making them promising for high-quality white-light generation. Finally, WLEDs based on as-obtained gradient alloy CdSe_1–xS_x NPLs are fabricated that show high luminous efficiencies (LE) reaching values up to 250 lm/W and CRI values as high as 91, demonstrating their potential for commercial applications.

中文翻译：

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高度发光的梯度CdSe _{1– x} S _x纳米片，具有减少的重吸收，可产生白光

胶体半导体纳米粒子在设计高质量的白光发光二极管（WLED）方面具有巨大的潜力。然而，由于特征性的小斯托克斯位移，纳米颗粒遭受重吸收效应，这限制了光源的功率转换效率。为了解决该问题，应当分离纳米颗粒的吸收和发射光谱。在这里，我们报道了梯度合金CdSe _{1– x} S _x纳米片（NPLs），它可以抑制重吸收。多亏了梯度成分，CdSe _{1– x} S _x的富S域NPL充当有效的天线，吸收光并将生成的载流子集中到富硒域中，并在其中进行重组。CdSe _{1- x} S _x NPLs的梯度结构使人们可以简单地通过改变其组成来控制发射光谱和吸收光谱的重叠。通过控制CdSe _{1- x} S _x NPL的成分，可以调整其光度参数，包括色度色坐标，显色指数（CRI）和相关色温（CCT）。由于与不饱和S / Se表面原子相关的宽陷阱辅助发射，CdSe _{1– x} S _xNPL在2509-6448 K范围内的CCT值下显示出极高的CRI值，范围从87到94，这使其有希望产生高质量的白光。最后，制造出的基于已获得的渐变合金CdSe _{1– x} S _x NPL的WLED表现出高达250 lm / W的高发光效率（LE）和高达91的CRI值，证明了其在商业应用中的潜力。