@article { ISI:000481931200016,
	title = {FAPbI(3) Flexible Solar Cells with a Record Efficiency of 19.38\% Fabricated in Air via Ligand and Additive Synergetic Process},
	journal = {ADVANCED FUNCTIONAL MATERIALS},
	volume = {29},
	number = {34},
	year = {2019},
	month = {AUG},
	abstract = {Compared with silicon-based solar cells, organic-inorganic hybrid perovskite solar cells (PSCs) possess a distinct advantage, i.e., its application in the flexible field. However, the efficiency of the flexible device is still lower than that of the rigid one. First, it is found that the dense formamidinium (FA)-based perovskite film can be obtained with the help of N-methyl-2-pyrrolidone (NMP) via low pressure-assisted method. In addition, CH3NH3Cl (MACl) as the additive can preferentially form MAPbCl(3-)(x)I(x) perovskite seeds to induce perovskite phase transition and crystal growth. Finally, by using FAI center dot PbI2 center dot NMP+x\%MACl as the precursor, i.e., ligand and additive synergetic process, a FA-based perovskite film with a large grain size, high crystallinity, and low trap density is obtained on a flexible substrate under ambient conditions due to the synergetic effect, e.g., MACl can enhance the crystallization of the intermediate phase of FAI center dot PbI2 center dot NMP. As a result, a record efficiency of 19.38\% in flexible planar PSCs is achieved, and it can retain about 89\% of its initial power conversion efficiency (PCE) after 230 days without encapsulation under ambient conditions. The PCE retains 92\% of the initial value after 500 bending cycles with a bending radii of 10 mm. The results show a robust way to fabricate highly efficient flexible PSCs.},
	issn = {1616-301X},
	doi = {10.1002/adfm.201902974},
	author = {Wu, Cuncun and Wang, Duo and Zhang, Yuqing and Gu, Feidan and Liu, Canghong and Ning Zhu and Luo, Wei and Dong Han and Guo, Xuan and Qu, Bo and Wang, Shufeng and Bian, Zuqiang and Chen, Zhijian and Xiao, Lixin}
}
