Luminescent transition metal complexes for organic light-emitting diodes and photocatalytic CO₂ reduction

Abstract

Nowadays, energy crisis and carbon dioxide (CO₂) emission have already been threats in the whole world. In the view of energy saving, the development of lighting, which occupies around 19% of the total power consumed on earth, is essential to improve the energy conversion efficiency. As a result, organic light-emitting diodes (OLEDs) have received much attention by scientists for lighting with lower power input at the same brightness. On the other hand, the CO2 conversion system by utilizing the solar energy is considered to be one of the most promising renewable energy sources and fulfil environmental requirements. However, the existing photocatalytic CO₂ reduction system is not efficient and durable enough for practical application, and a standard criterion is still not built. This provides research opportunities for the improvement of photocatalytic efficiency and investigation of the relationship between molecular design and functional properties. The basic concepts and conspectuses regarding organic light-emitting diodes and light-driven carbon dioxide reduction are collected in Chapter 1. In Chapter 2, five series of twenty carbene-metal-amide complexes with copper(I) or silver(I) metal center and two coordinated ligands are presented as possible dopants for organic light-emitting diodes. The discussion is focused on its interesting photophysical properties. Importantly, the structure-property relationship is studied by modifying the two coordinated ligands, N-heterocyclic carbene ligands as electron acceptors and amide ligands as electron donors. Although the primary results of vacuum-processed OLEDs are collected and presented, optimization of OLEDs is further required. Besides, solution-processed OLEDs are more suitable for this family of complexes based on observation. In Chapter 3, the studies of photophysical properties and tests of photocatalytic CO₂ reduction were conducted using two series of iridium(III) photosensitizers. One has the same neutral N-heterocyclic carbene ligand and different C^N ligands. The other one has the same C^N ligand and different N-heterocyclic carbene ligand attached with pyrene functional group. The pyrene chromophore inducing reversible electronic energy transfer is accounted. Finally, Chapter 4 presents the concluding remarks and possible future works, while Chapter 5 includes all the experimental details in Chapter 2 and Chapter 3.