Manipulation of excited states in organic-inorganic hybrid perovskite optoelectronic devices

In recent years, a huge success on photovoltaic and light emitting has been achieved in the field of organic-inorganic hybrid perovskites owing to the superior optoelectronic properties of excited states. Regulating the primary excited states is the foundation of developing multi-functional optoelectronics, including the light-emitting, photovoltaic and lasing actions. By revisiting the photophysical processes of excited states, some new strategies are suggested to further pushing the efficiency of perovskites forward. This thesis focuses on the manipulation of excited states through combining optoelectronic devices, from excited states generation to excited charge carrier transport.

Chapter 1 presents a basic introduction to excited states in semiconductors and some optoelectronic applications of organic inorganic hybrid perovskites. Chapter 2 demonstrates charge-transfer excitons in 2D perovskite heterostructures. In this chapter, we first discover charge-transfer excitons in 2D perovskite heterostructure (PEA₂PbI₄/PEA₂SnI₄), which opens up the potential applications in perovskite LEDs and photodetectors. Chapter 3 reveals doping enhanced orbit-orbit interaction in Sn based perovskites and Chapter 4 introduces long-order orbital interaction through slow hot-carrier cooling. In these two chapters, we explore the possible strategies to increase the population of dark states through orbit-orbit interaction toward highly efficient quasi-2D perovskite solar cells and lead-free perovskite solar cells. Chapter 5 proposes a new strategy (uniform permutation of 2D nanoplates) in quasi-2D perovskite films toward efficient charge collection and Chapter 6 realizes AC electroluminescence in quasi-2D perovskite LEDs. In these two chapters, we propose a new strategy to facilitate bipolar carrier transport in quasi-2D perovskite films toward world record high fill factor in quasi-2D perovskite solar cells and efficient alternating current driven LED. Chapter 7 summarizes the entire studies in this dissertation.