Fabrication of PNC optoelectronics
ITO-coated glass substrates were cleaned in an ultrasonic bath with detergent, deionized water, acetone, and isopropanol for 15 min and dried in the oven at 80 ◦C overnight.
After treatment with UV/ozone for 30 min, PEDOT:PSS (AI4083) was spin-coated onto the ITO-coated glass substrate at 4500 rpm for the 40 s and dried for 10 min at 140 °C in air. Then poly-TPD (12 mg mL-1 in chlorobenzene (CB)) solution was spin-coated onto the PEDOT:PSS layer at 4000 rpm for 40 s followed by annealing at 120 °C for 5 min in the glovebox. TFB (16 mg mL-1 in xylene) layer was spin-coated on poly-TPD layer at 4000 rpm for 40 s and annealed at 150 °C for 30 min.
The PNC emissive layer was spin-coated on HTL layer at 2000 rpm for 20 s.
Finally, TPBi (75 nm), LiF (1 nm) and Al (100 nm) were sequentially deposited by thermal evaporation under ~10–6 Torr. The full structure of the device was : ITO/PEDOT:PSS/Poly-TPD/TFB/PNCs/TPBi/LiF/Al.
Figure 1. (a) Schematics depicting the respective device architectures of PNC-based LEDs. (b) corresponding PNC matrices that are employed as an emissive layer for the LEDs. (c) J-V-L, and (d) EQE curves of the LED devices, respectively. (e) EL spectra of target LED.
Table 1. Summarized performance of the LED device.
Characterization
XRD spectra of the PNCs were collected using a Rigaku SmartLab diffractometer. SEM images were taken with Verios G4 UC (FEI) SEM instrument equipped at the Hanyang LINC + Analytical Equipment Center. J–V–L characteristics and device performances were measured using a Konica Minolta spectroradiometer (CS-2000) with a Keithley 2400 sourcemeter. UPS measurements were conducted using a photoelectron spectrometer (Thermo Fisher Scientific, Theta Probe) installed at the Hanyang LINC+ Analytical Equipment Center. For UPS measurements, Al Kα (1486.7 eV) and He I (21.22 eV) beamlines were, respectively, used. A fixed sample-to-detector angle of 30° was used to mainly collect surface-oriented signals.