Red C-dots and C-dot films: solvothermal synthesis, excitation-independent emission and solid-state-lighting

Abstract

a Currently, fluorescent carbon dots (CDs) have attracted great attention for their unique optical performance. However, the shortage of red emissive CDs and the corresponding CD solid samples with intense luminescence significantly limit their applications in optoelectronic fields. In the present work, red fluorescence CDs were successfully synthesized via a facile solvothermal reaction using pphenylenediamine as the carbon source and isopropanol as the solvent. Excitation-independent luminescence and emission-independent decay indicated that one dominant type of emissive state was responsible for red luminescence, which was evidenced to be a N-related surface defect state with the help of structural and spectroscopic characterizations. Furthermore, CD-embedded PVA solid films, exhibiting bright red emission with intense absorption in the blue-light region, were prepared to explore their possible application as a color converter in solid-state lighting. As a proof-of-concept experiment, white light-emitting diode devices were constructed by combining a red CD solid film and yellow Ce:YAG phosphor-in-glass with a commercial InGaN blue chip, showing tunable color coordinates, color rendering index and correlated color temperature via modifying the thickness of the CD film.

Bright Electroluminescent White‐Light‐Emitting Diodes Based on Carbon Dots with Tunable Correlated Color Temperature Enabled by Aggregation

“…The characteristic G band centered at ≈1588 cm −1 can be attributed to the graphitic sp 2 carbon, while the D band centered at 1388 cm −1 originates from defects on the surface of Y‐CDs. [ 17 ] The intensity ratio of I G / I D is ≈1.16, indicating a high degree of crystallinity of the as‐prepared Y‐CDs.…”

Gram‐Scale Room‐Temperature Synthesis of Solid‐State Fluorescent Carbon Nanodots for Bright Electroluminescent Light Emitting Diodes

“…The G to D intensity ratio (I G /I D ) was calculated to be 1.4, further implying the good crystallinity of RT-CDs. [35,36] Figure 2b presents the recorded Fourier transform infrared spectrum data of the RT-CDs. The broad absorption peak located at 3410 cm −1 is associated with the strong stretching vibration of N-H bonds.…”

Solid‐State, Hectogram‐Scale Preparation of Red Carbon Dots as Phosphor for Energy‐Transfer‐Induced High‐Quality White LEDs with CRI of 97

“…Currently, only a few studies reported the synthesis of C-dots on a hectogram scale, [24][25][26][27][28][29][30] not mentioning majority of these reports only achieved blue-and green-emissive C-dots with relatively low yields. [24][25][26][27][28][29] Secondly, current WLEDs constructed from red C-dots and YAG generally suffered from poor color coordinates, [31][32][33][34] low CRI, [32,33,35,36] or pool CCT [37] (Table S1, Supporting Information, entries 1-7) due to the (Carbon 2022, 192, 198-208) for the synthesis of red C-dots via the microwaveassisted hydrothermal treatment of o-phenylenediamine, in which there were many impurities due to the less controlled molecular orientation and stacking as well as complicated purifications. b) Scheme showing the convenient synthesis of red C-dots in a cleaner, convenient, and safer manner via pre-crystallization-assisted solid-state calcination of o-phenylenediamine developed in this study.…”