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Since the first report on the solid-state perovskite solar cell with power conversion efficiency (PCE) of 9.7% in 2012 by our group, its certified PCE now reaches 22%. It is believed that perovskite solar cell is promising next-generation photovoltaics (PVs) due to superb performance and very low cost. In this talk, the history of perovskite photovoltaics will be briefly presented along with their scientific progress. Methodologies to achieve hysteresis-free, stable and high PCE perovskite solar cells will be introduced. Lewis acid-base adduct approach has been found to be very reliable and reproducible method to get high quality perovskite layer minimizing non-radiative recombination. Non-stoichiometric precursor in adduct process demonstrated grain boundary healing effect, which further improved voltage and fill factor due to long carrier life time of perovskite and improved charge transporting at grain boundary as well. Grain boundary healing process yields PCE as high as 20.4%. Moisture was effectively protected and hysteresis was significantly reduced by introducing 2-dimensioanl perovskite at grain boundary of 3-dimensional perovskite grains. Ion migration is one of factors affecting stability and hysteresis, which can be deactivated by 2-dimensional perovskite with higher barrier energy for ion migration. Thermal stability of perovskite material was found to be stable up to 120°C in the absence of moisture, but that of full device was sensitive to selective contacts, indicating that thermally stable selective contacts are equally important. Universal method to remove hysteresis will be also given in this talk.
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