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研究生： 唐翰
MUJAHID, ANAS
論文名稱： 有機共軛分子二極體單重態裂變與三重態湮滅上轉換反應
SINGLET FISSION AND TRIPLET–TRIPLET ANNIHILATION UPCONVERSION REACTIONS IN ORGANIC CONJUGATED MOLECULE DIODES
指導教授： 郭宗枋
Guo, Tzung-Fang
學位類別： 博士
Doctor
系所名稱： 理學院 - 光電科學與工程學系
Department of Photonics
論文出版年： 2026
畢業學年度： 114
語文別： 英文
論文頁數： 132
外文關鍵詞： singlet fission, triplet-triplet annihilation, sub-bandgap, above bandgap energy
ORCID： 0009-0004-0719-0430
ResearchGate： https://www.researchgate.net/profile/Anas-Mujahid-2/research
相關次數： 點閱：5  下載：0 
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    • First, this dissertation establishes that magneto-electroluminescence (MEL) measurements must be performed under constant-current conditions. At constant voltage, the MEL response is mediated by magnetoconductance (MC), leading to misinterpretation. This is systematically validated in both polymer-based and TADF organic light-emitting diodes, providing a critical guideline for reliable magnetic field characterization.
    Second, it validates the possibility of utilizing the above-bandgap excitation energy through the endothermic singlet fission (SF) process. Using tetracene as a model, excitation-energy-dependent SF is revealed by magneto-photoluminescence, showing a breakdown of Kasha’s rule, where high-energy excitation yields a higher degree of SF. Endothermic SF proceeds via ultrafast formation of a correlated triplet–triplet 1(TT) pair followed by thermally activated triplet separation. Device-level validation confirms SF-assisted photocurrent generation, with enhanced IPCE in the 300-400 nm region contributing ~33% of total short-circuit current. Incorporation of a C60 acceptor enabling ultrafast charge transfer (~0.5 ps) suppresses this SF-related feature, confirming SF-mediated photocurrent generation.
    Finally, the dissertation uncovers the overlooked back charge separation (BCS) effect in sub-bandgap rubrene/C60 devices, where the charge transfer (CT) state acts as a recombination zone, and emission is obtained from rubrene through the triplet–triplet annihilation (TTA) upconversion process. BCS limits luminance and rapidly reduces EQE. Rubrene thickness optimization and interfacial engineering mitigate BCS but shift recombination from TTA to SF. Introducing FRET dopants bypasses BCS and enhances EQE by an order of magnitude via efficient TTA, with all mechanisms confirmed by magnetic field effect measurements.

    ABSTRACT I ACKNOWLEDGEMENTS II TABLE OF CONTENTS IV LIST OF FIGURES VIII LIST OF ACRONYMS X CHAPTER 1 INTRODUCTION 1 1.1 Background 1 1.2 Overview of organic devices 2 1.3 Magnetic field effects in organic devices 6 1.4 Motivation of the research 7 1.5 Objectives and scope of the thesis 8 CHAPTER 2 LITERATURE REVIEW 10 2.1 Overview of organic semiconductors 10 2.2 Exciton dynamics: singlets and triplets 11 2.3 Role of exciton dynamics and spin physics 12 2.4 Brief overview of magnetic field effects in organic semiconductors 14 2.5 Theoretical models of magnetic-field effects 16 2.5.1 Polaron pair model 17 2.5.2 Bipolaron model 18 2.5.3 Δg model 19 2.5.4 Exciton model 20 2.6 Singlet fission 22 2.6.1 Exothermic singlet fission 23 2.6.2 Endothermic singlet fission 24 2.7 Triplet-triplet annihilation upconversion 24 2.8 Thermally activated delayed fluorescence process 26 2.9 Summary and research gaps 28 2.9.1 First research gap 28 2.9.2 Second research gap 29 2.9.3 Third research gap 30 CHAPTER 3 DEVICE FABRICATION AND MEASUREMENTS 32 3.1 Fabrication 32 3.1.1 ITO electrode patterning via photolithography 32 3.1.2 Substrate cleaning 32 3.1.3 Soft bake 33 3.1.4 UV exposure 33 3.1.5 Development 33 3.1.6 Hard bake 33 3.1.7 Etching 33 3.1.8 Final cleaning 33 3.2 Final fabrication process 34 3.3 Chemical structures of materials used in this dissertation 36 3.4 Measurement setup 37 3.4.1 Electrical characterization 37 3.4.2 MEL and MC measurements 37 3.4.3 MPL measurement 41 3.4.4 IPCE measurement 41 3.4.5 Femtosecond transient absorption measurement analysis 43 3.4.6 Theoretical data analysis 45 CHAPTER 4 MAGNETOELECTROLUMINENCE RESPONSES MEDIATED BY MAGNETOCONDUCTANCE IN POLYMER AND TADF-BASED LEDS 46 4.1 Introduction 46 4.2 Theoretical framework and device structure 48 4.2.1 The SYPPV-based device with balanced charge carrier dynamics 49 4.2.2 The energy band diagram of the TADF-based device with unbalanced charge carrier dynamics 50 4.2.3 The energy band diagram of the TADF-based device with balanced charge carrier dynamics 52 4.3 Experimental results and discussion 54 4.4 Summary 66 CHAPTER 5 ENDOTHERMIC SINGLET FISSION PROCESS IN HARVESTING THE HIGH-LEVEL EXCITATION ENERGY FOR TETRACENE-BASED PHOTODIODE 67 5.1 Introduction 67 5.2 Experimental results and discussion 71 5.3.1 Endothermic SF in a practical organic photodiode 80 5.4 Summary 86 CHAPTER 6 UNPRECEDENTED EXTERNAL QUANTUM EFFICIENCY BOOST IN SUB-BANDGAP OLEDS 87 6.1 Introduction 87 6.2 Discussion 89 6.2.1 Blocking interface method 90 6.2.2 Thickness-dependent recombination 91 6.3.1 Enabling FRET by introducing a dopant 91 6.3 Summary 92 CHAPTER 7 CONCLUSION AND FUTURE WORK 93 7.1 Conclusion 93 7.2 Future work 95 7.2.1 Singlet fission-enabled UV photodetectors 95 7.2.2 Singlet fission energy transfer to perovskites 97 7.2.3 Sub-bandgap OLEDs enabled by controlled CT-FRET balance 98 REFERENCES 99 LIST OF PUBLICATIONS 120 LIST OF RECEIVED AWARDS 120

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