Title Page
Contents
Abstract 9
Chapter 1. Introduction 10
1.1. History of Perovskite Nanocrystals 10
1.2. Development of Perovskite LEDs 14
1.3. Working Principle of Perovskite LEDs 16
1.4. Characterization of Perovskite LEDs 18
1.4.1. Turn-on and Operating Voltage 18
1.4.2. Device Efficiency 19
Chapter 2. Research Background 20
Chapter 3. Experiment section 22
3.1. Materials 22
3.2. Preparation of DDAF precursor 23
3.3. Synthesis of CsPbBr₃ nanocrystals 23
3.4. Synthesis of Cadmium acetate treated CsPbBr₃ Nanocrystals 24
3.5. Device fabrication and characterization 25
Chapter 4. Result and Discussion 26
4.1. Concept of Surface passivation and TEM & PXRD analysis 26
4.2. Fourier-transform infrared spectroscopy and Optical analysis 30
4.3. Electrical analysis on PNCs and Perovskite LED 35
Chapter 5. Conclusion 42
Reference 43
Table 1. Summarized device performances with pristine and CdAc treated device 39
Figure 1. Structure of perovskite materials 11
Figure 2. Working principle of perovskite LEDs 17
Figure 3. Schematic band diagrams of perovskite LEDs 19
Figure 4. Schematic illustration of PNCs defect passivation and ligand exchange process 26
Figure 5. High magnification TEM image of pristine and CdAc treated CsPbBr₃ nanocrystals, size histogram of PNCs (inset) 27
Figure 6. Low magnification TEM image of pristine and CdAc treated CsPbBr₃ PNCs and EDS mapping images of Cs, Pb, Cd and Br atoms 28
Figure 7. Powder X-ray diffraction pattern for pristine and CdAc treated PNCs 29
Figure 8. Fourier-transform infrared spectroscopy of neat, pristine and CdAc treated PNCs 30
Figure 9. Normalized absorption and PL spectra and UV-visible absorption of the pristine and CdAc treated PNCs 31
Figure 10. PL decay curves of the pristine and CdAc treated PNCs 32
Figure 11. Solution PLQY plots of the pristine and CdAc treated PNCs 33
Figure 12. Time dependent storage film PLQY plots of the pristine and CdAc treated PNCs 34
Figure 13. Photo of Time dependent storage film of the pristine and CdAc treated PNCs 34
Figure 14. J-V characteristics of hole-only devices with VTFL kink point behavior in pristine and CdAc treated PNCs films.[이미지참조] 36
Figure 15. Energy level diagram of perovskite LED device 37
Figure 16. UPS spectra of pristine and CdAc treated PNCs 38
Figure 17. a) Current density–voltage (J–V) curves of perovskite LED device. b) Luminance–voltage (L–V) curves of perovskite LED device. c) Current density–EQE... 38
Figure 18. EL spectra with voltage from 2.7 V to 4.5 V 39
Figure 19. Operational stability of pristine and CdAc treated perovskite LEDs measured at each current densities 41
Figure 20. EL spectra at each point of operation 41
Figure 21. The temperature of both devices measured with an IR thermal imaging camera during the device's operation 42