PTAA/TPBi Host–Guest Engineering Enables High‐Brightness Yellow Carbon Dot Based Light‐Emitting Diodes through Electron Confinement

Abstract Carbon dots have been extensively studied as a ‐stable, tunable, and environmentally friendly light‐emitting material in light‐emitting diodes. However, it has been found that no matter how the properties of carbon dots (CDs) are optimized, the device performance is still unsatisfactory, and even solid‐state CDs with high quantum yields do not necessarily imply better device performance. In this study, CDs are doped into host materials— to form an emissive layer. When excited by an applied electric field, the CDs act as luminescent guest molecules, while the host material provides the desired charge transport properties and stability. This method‐ improves the morphology of the emissive layer and balances the charge transport and distribution, thus increasing the charge compounding efficiency and improving the device performance, with poly[bis(4‐phenyl)(2,4,6‐trimethylphenyl)amine] as the hole transport layer and 1,3,5‐tris(1‐phenyl‐1H‐benzimidazol‐2‐yl)benzene as the host material doped with CDs, the luminance is as high as 9754 cd m −2 and the efficiency is 8.53 cd A −1 . The results of the study show that in addition to the synthesis of highly efficient solid‐state fluorescent CDs, the design of the device structure and the development of more efficient hole‐transporting materials are also key factors to improve the performance of CDs‐based light‐emitting diodes.