Fundamental Properties And Interface Researches On Methylammonium Lead-Halide Perovskite

As a kind of clean and renewable energy resource, solar energy plays significant role in national economic and people’s daily life. Photovoltaic solar cell is regarded as one of the most promising way to store and utilize solar energy. However, the traditional inorganic silicon solar cell is limited in mass production by the high cost and sophisticated producing technology. Novel organic photovoltaic device can meet these features, its relative low power conversion efficiency（PCE）, however, turning into the key deficiency. The superb carrier mobility and broad light absorption abilities of methylammonium lead-halide perovskite have evoked tremendous interests in the whole world, since it was first introduced into photovoltaic field in 2009. With six years advances, perovskite based solar cell has achieved 20% in PCE, which is an undisputed grand breakthrough. However the operation mechanism in the high-performance device remains unclear. Thus a series of related fundamental work are urgently needed, for the guidance of perfect device design and manufacture.In this thesis, we utilize many characterization techniques for measurement. They are Photoemission Energy Spectroscopy（PES）, Inverted Photoemission Energy Spectroscopy（IPES）, Scanning Electron Microscopy（SEM）, Ultraviolet-visible Spectroscopy（UV-vis） and Powder X-ray Diffraction Spectroscopy（XRD）. These techniques allowed us to measure the electronic structure, surface morphology and crystal structure of perovskite. Further energy level alignment study at perovskite/organic interface was also investigated. More details are listed below,（1） Firstly, we investigated the impact of film manufacture factors, such as solution concentration, spin coating speed, annealing temperature and time etc., to the film morphology, crystallinity and electronic structure. Final results shows that the 40 wt. % perovskite precursor solution spin coated with 6000 rpm for 40 seconds on ITO substrate, following by 40 minutes annealing at 110 oC will finally lead to the best film morphology. Further analysis indicate that among all these investigated factors, annealing temperature is the most influential one. High temperature especially when it is beyond 120 oC, perovskite film can be decomposed.（2） Then we pay attention to the halogen composition effect. While introducing another halogen into CH₃NH₃PbX₃, the original features would tuning respectively. The experimental result reveals that the extent of energy level shift and crystal diffraction position changing is bound up with the quantity of introduced halogen. The features of doped perovskite always deriving from the combination of those two tri-halide perovskites. Besides, no brand new electronic or optical features are discovered in our experiments.（3） At last, the energy level alignment at perovskite/organic interface was investigated by in-site UPS and XPS. FAPbI₃ and MAPbI₃ are chosen as substrate deliberately, due to their high performance in recent solar cell device. No obvious energy level alignment discrepancy was observed as they contact with organics. However in some cases tiny difference could appear. So, more experiments should be taken before we treat them as the same.