| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 1263638 | Organic Electronics | 2015 | 6 Pages |
•Violet cadmium-free quantum dot-based light-emitting diodes (QD-LEDs) were demonstrated.•The performance of QD-LEDs was optimized by selecting the hole transport materials.•Violet QD-LEDs with high efficiency and low turn-on voltage could be obtained via controlling the amount of TFB mixed PVK.•No obvious broad emission could be recorded in all the regions of the EL spectrum of TFB–PVK mixture HTL devices.
Bright and efficient violet quantum dot (QD) based light-emitting diodes (QD-LEDs) with heavy-metal-free ZnSe/ZnS have been demonstrated by choosing different hole transport layers, including poly(4-butyl-phenyl-diphenyl-amine) (poly-TPD), poly[9,9-dioctylfluorene-co-N-[4-(3-methylpropyl)]-diphenylamine] (TFB), and poly-N-vinylcarbazole (PVK). Violet QD-LEDs with maximum luminance of about 930 cd/m2, the maximum current efficiency of 0.18 cd/A, and the peak EQE of 1.02% when poly-TPD was used as HTL. Higher brightness and low turn-on voltage (3.8 V) violet QD-LEDs could be fabricated when TFB was used as hole transport material. Although the maximum luminance could reach up to 2691 cd/m2, the devices exhibited only low current efficiency (∼0.51 cd/A) and EQE (∼2.88%). If PVK is used as hole transport material, highly efficient violet QD-LEDs can be fabricated with lower maximum luminance and higher turn-on voltages compared with counterpart using TFB. Therefore, TFB and PVK mixture in a certain proportion has been used as HTL, turn-on voltage, brightness, and efficiency all have been improved greatly. The QD-LEDs is fabricated with 7.39% of EQE and 2856 cd/m2 of maximum brightness with narrow FWHM less than 21 nm. These results represent significant improvements in the performance of heavy-metal-free violet QD-LEDs in terms of efficiency, brightness, and color purity.
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