Molecular Design of Opto-Electronic Materials

Zhen Li has been a full professor at Wuhan University since 2006, a chair professor at Tianjin University since 2018, and Vice President of Hubei University since 2025, China. His research focuses on polymeric optoelectronic materials, their mechanisms, and applications.

• Preface xi1 A Brief Introduction to Molecular Aggregates 1Jiaqiang Wang, Juqing Gu, Guigui Ye, Wei Cao, Meng Wang, Changzun Jiang, Shuhui li, Arui Huang, Qianqian li, and Zhen li1.1 Introduction 11.1.1 Motivation 11.1.2 A Brief History 41.1.3 Basic Knowledge of Organic Compounds in Aggregated States 71.1.3.1 The Driving Force of Molecular Aggregates 71.1.3.2 The Adjustment of Molecular Interactions in Molecular Aggregates 101.1.4 Overview of Topics Covered 13References 172 The Molecular Engineering and Fabrication Processes for Molecular Aggregates 33Yujie Yang, Boxi Wu, Wentao Yuan, Shiyue Tang, Panpan Qiao, Yifan Niu, Peidong Xie, Ruixing Wang, Yan Gao, Yuexin Li, Wanni Yao, Kai Wang, Qianqian li, and Zhen li2.1 Crystal Engineering 332.1.1 Organic Crystals Grown from Solution 342.1.1.1 Solvent Evaporation Method 342.1.1.2 Slow Cooling Method 362.1.1.3 Vapor Diffusion Method 362.1.1.4 Liquid–Liquid Diffusion Method 372.1.2 Vapor Phase Growth Method 372.1.3 Melt Growth 372.1.3.1 Bridgman–Stockbarger Method 382.1.3.2 Subcooled Melt Method 382.1.3.3 Zone-melting Recrystallization 392.1.3.4 Czochralski Growth Method 402.1.3.5 Laser Heating Base Method 402.2 Self-assembly System 412.2.1 Drivers of Molecular Self-assembly 412.2.1.1 Hydrogen Bonding Interactions 412.2.1.2 Hydrophobic Effect 422.2.1.3 Electrostatic Interactions 432.2.1.4 ​π–π​ Interaction 432.2.1.5 Coordination Interactions 432.2.2 Aggregation Types in Molecular Self-assembly 442.2.2.1 Nanoparticles 442.2.2.2 Membranes 442.2.2.3 Micelles 452.2.3 Control Methods of Molecular Self-assembly 452.2.3.1 Stimuli-responsive Self-assembly 462.2.3.2 Solvent Evaporation Self-assembly 462.2.3.3 Template-guided Self-assembly 482.2.3.4 Adsorption-based Self-assembly 482.3 Gel System 492.3.1 Chemical Gels 502.3.1.1 Free Radical Polymerization 502.3.1.2 Dynamic Covalent Cross-linking 512.3.1.3 Radiation Cross-linking 522.3.2 Supramolecular Gels 532.3.2.1 Electrostatic Interactions 532.3.2.2 Hydrophobic Interactions 542.3.2.3 Crystallization 552.3.2.4 Hydrogen Bonding 552.3.2.5 Ligand Binding 562.3.2.6 Host–Guest Interaction 582.4 Cross-linking System 592.4.1 Chemical Cross-linking 592.4.1.1 Triggered by Chemical Agents 592.4.1.2 Triggered by Heat 602.4.1.3 Triggered by Light 612.4.1.4 Triggered by Radicals 612.4.2 Physical Cross-linking 622.4.2.1 Physical Entanglement 632.4.2.2 Hydrogen Bonding 632.4.2.3 Crystallization 632.4.2.4 Ionic Interactions 632.4.2.5 Self-assembly and Supramolecular Interactions 632.4.3 Radiation Cross-linking 632.4.4 The Advantages of Cross-linking in the Regulation of Aggregated Structures 642.4.4.1 Fixed Orientation and Structural Stability 642.4.4.2 Enhanced Mechanical Properties 652.4.4.3 Dynamic Covalent Bonding for Adaptive Materials 662.5 Host–Guest System 672.5.1 Non-covalent Interactions in the Host–Guest System 682.5.1.1 Hydrogen Bonding 682.5.1.2 Hydrophobic Interactions 692.5.1.3 Electrostatic Interactions 692.5.1.4 ​π–π​Interactions 702.6 Conclusion 70References 703 The Research Methodology of Molecular Aggregation Science 87Jiajia Song, Aisen li, Kun Yang, Weilong Che, and Zhen li3.1 The Theoretical Calculation 873.1.1 Introduction 873.1.2 Overview of Quantum Chemistry Calculation 883.1.2.1 Ab Initio Calculation 893.1.2.2 Density Functional Theory 913.1.2.3 Semiempirical Molecular Orbital Methods 923.1.3 Calculation Software 943.1.3.1 Gaussian 943.1.3.2 Vasp 943.1.4 Calculation of the Properties of Semiconductor Opto-electronic Materials 953.1.4.1 Structure Optimization 953.1.4.2 Band Structure and Density of States 963.1.4.3 Thermodynamic Stability and Chemical Formation Energy 963.1.4.4 Carrier Effective Mass 963.1.4.5 Optical Absorption Spectrum 993.1.4.6 Exciton and Binding Energy of Exciton 1003.1.5 Conclusion and Outlook 1013.2 General Methods 1023.3 Other Methods (Pressure, Light, and Temperature) 1083.3.1 Pressure 1093.3.1.1 Mechanical Grinding 1103.3.1.2 Hydrostatic Pressure 1123.3.2 Light 1143.3.3 Temperature 1163.3.4 Chemical Substances 117References 1194 Photoluminescence of Molecular Aggregates 125Jie Yang, Manman Fang, and Zhen li4.1 Introduction 1254.2 Fluorescence 1274.2.1 Aggregation-induced Emission 1274.2.2 Excimer 1304.2.3 J/H/X Aggregate 1334.3 Thermally Activated Delayed Fluorescence (TADF) 1374.3.1 Generation of Delayed Fluorescence 1374.3.2 Aggregation-induced Delayed Fluorescence 1384.3.3 Through-space Charge Transfer based TADF 1414.3.4 Exciplex-based TADF 1434.4 Phosphorescence 1454.4.1 Room-temperature Phosphorescence 1454.4.2 Nonaromatic Room-temperature Phosphorescence 1494.4.3 Long Persistent Luminescence 1524.5 Conclusion 155References 1555 Mechanoluminescence of Molecular Aggregates 163Yujun Xie, Jinfeng Wang, and Zhen li5.1 The Emission Mechanism of Mechanoluminescence 1635.1.1 Brief Introduction to the History of Organic Mechanoluminescence 1635.1.2 ml Derives from the Gas Discharge of Organic Crystal Without Luminescent Center 1655.1.3 ml from the Organic Compounds Contain Luminescent Center 1675.2 Organic Crystals with Fluorescent Mechanoluminescence 1695.2.1 Triphenylamine Derivatives 1695.2.2 Tetraphenylethylene Derivatives 1725.2.3 N-containing Heterocyclic Derivatives 1785.3 Organic Crystals with Phosphorescent Mechanoluminescence 1865.4 Mechanoluminescence from Doping System 1885.5 Special Mechanoluminescence Phenomena 1915.6 Summary 192References 1936 Molecular Aggregates as Charge Transport Layers in Perovskite Solar Cells 199Shuyan Shao and Zhen li6.1 Introduction 1996.2 Construction and Work Principle 2026.2.1 Device Structure 2026.2.2 Work Principle 2036.3 Small Molecules as Hole Transport Layers in HPSCs 2046.3.1 Chemically Doped Small Molecule HTLs 2056.3.2 Dopant-free Small Molecule HTLs 2186.3.2.1 Undoped HTLs in n-i-p Structure 2196.3.2.2 Undoped HTMs in p-i-n Structure 2216.4 Small Molecules as ETLs in HPSCs 2236.4.1 Fullerene and Derivatives 2236.4.2 Non-fullerene Small Molecules 2276.4.2.1 Perylene Diimides (PDIs) as ETLs in HPSCs 2276.4.2.2 NDIs as ETLs in HPSCs 2316.4.2.3 Azaacene-based Small Molecules as ETLs in HPSCs 2336.4.2.4 IDT-based Small Molecules as ETLs in HPSCs 2346.4.2.5 Other Small Molecules as ETLs 2376.5 Conclusion 238References 2397 Molecular Aggregates as Active Layers in Organic Solar Cells 245Jin He, Yibin li, Zhong’an li, and Zhen li7.1 Introduction 2457.1.1 Effects of Donor Aggregates 2487.1.1.1 Effects of Acceptor Aggregates 259References 2738 Molecular Aggregates for Second-order Nonlinear Optical Effect 281Wenbo Wu and Zhen li8.1 Microscopic and Macroscopic Nonlinearities of Organic Systems 2818.2 Organic Molecules for Second-order Nonlinear Optics 2848.3 Polymers for Second-order Nonlinear Optics 2878.4 Summary and Perspective 301Acknowledgements 302References 3029 Other Opto-electronic Materials in Aggregate 311Shaoqiang Dong, Meiting Zhao, Zhijun Ruan, Zekun Tong, Yutian Qin, Chaoyang Zheng, Xinfang Zhang, and Zhen li9.1 Magnetic Materials 3119.1.1 Introduction 3119.1.2 Molecular Magnetic Materials 3119.1.3 Summary and Perspective 3229.2 Metal–Organic Frameworks 3229.2.1 Introduction 3229.2.2 Structure of Opto-electronic MOFs 3239.2.2.1 TBAPy-based MOFs 3249.2.2.2 TCBPE-based MOFs 3259.2.2.3 TCPP-based MOFs 3269.2.2.4 Other MOFs 3289.2.3 Properties of Opto-electronic MOFs 3309.2.4 Summary 3329.3 Covalent Organic Frameworks 3339.3.1 Introduction 3339.3.2 Construction of COFs with Different Aggregation States 3349.3.3 Properties of COFs with Different Aggregation States 3369.3.3.1 Optical Properties of COFs 3369.3.3.2 Semiconducting Properties of COFs 3399.3.4 Summary and Perspectives 3429.4 Organic Radical Materials 3439.4.1 Introduction 3439.4.2 Triarylmethyl-based Fluorescent Radical Materials 3439.4.3 ​π-conjugated Conductive Radical Materials 3529.4.4 Charged Radical Materials 3589.4.5 Room-temperature Ferromagnetic Radical Materials 3619.4.6 Summary and Perspective 362References 36310 Conclusions and Outlook 377Zhen liIndex 379