Abstract
Using poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) as hole conductor, a series of inverted planar CH3NH3PbI3−xClx perovskite solar cells (PSCs) were fabricated based on perovskite annealed by an improved time-temperature dependent (TTD) procedure in a flowing nitrogen atmosphere for different time. Only after an optimum annealing time, an optimized power conversion efficiency of 14.36% could be achieved. To understand their performance dependence on annealing time, an in situ real-time synchrotron-based grazing incidence X-ray diffraction (GIXRD) was used to monitor a step-by-step gradual structure transformation from distinct mainly organic-inorganic hybrid materials into highly ordered CH3NH3PbI3 crystal during annealing. However, a re-crystallization process of perovskite crystal was observed for the first time during such an annealing procedure, which helps to enhance the perovskite crystallization and preferential orientations. The present GIXRD findings could well explain the drops of the open circuit voltage (Voc) and the fill factor (FF) during the ramping of temperature as well as the optimized power conversion efficiency achieved after an optimum annealing time. Thus, the present study not only illustrates clearly the decisive roles of post-annealing in the formation of solution-processed perovskite to better understand its formation mechanism, but also demonstrates the crucial dependences of device performance on the perovskite microstructure in PSCs.
Highlights
As well as the physical characters of the perovskite film are known to be critical to the film crystalline, morphology and devices performance[10,14,15,16,17,18]
Single halide perovskite film is typically prepared by mixing metal halide and organohalide containing the same halogen, which often shows poor quality induced by extensive crystallization caused by solvent evaporation as well as strong ionic interactions between the metalcations and the halides during the annealing treatment process; On the other hand, mixed halide perovskite film is typically prepared using precursors containing more than one halogens which is found to effectively improve the crystalline and morphology of perovskite films due to the removal of excess CH3NH3+ ions with the help of Cl− ions during the post-annealing process[26,38]
In order to understand how annealing time influence the performance of perovskite solar cells (PSCs), in situ real time two dimensional (2D) synchrotron-based grazing incidence X-ray diffraction (GIXRD), which is briefly illustrated in Fig. 1(b), was used to investigate the annealing process of CH3NH3PbI3−xClx perovskite thin films, during which a step-by-step gradual transformation was found from distinct mainly organic-inorganic hybrid materials into highly ordered CH3NH3PbI3 crystals
Summary
Yingguo Yang1,2,*, Shanglei Feng1,2,*, Meng Li3,*, Weidong Xu3, Guangzhi Yin[1,2], Zhaokui Wang[3], Baoquan Sun3 & Xingyu Gao[1,2]. After an optimum annealing time, an optimized power conversion efficiency of 14.36% could be achieved To understand their performance dependence on annealing time, an in situ real-time synchrotron-based grazing incidence X-ray diffraction (GIXRD) was used to monitor a step-by-step gradual structure transformation from distinct mainly organicinorganic hybrid materials into highly ordered CH3NH3PbI3 crystal during annealing. In order to understand how annealing time influence the performance of PSCs, in situ real time two dimensional (2D) synchrotron-based GIXRD, which is briefly illustrated, was used to investigate the annealing process of CH3NH3PbI3−xClx perovskite thin films, during which a step-by-step gradual transformation was found from distinct mainly organic-inorganic hybrid materials into highly ordered CH3NH3PbI3 crystals. Of solution-processed perovskite, and demonstrates the crucial dependences of device performance on the perovskite microstructure in PSCs
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