Deciphering the NH4PbI3 Intermediate Phase for Simultaneous Improvement on Nucleation and Crystal Growth of Perovskite
Deciphering the NH4PbI3 Intermediate Phase for Simultaneous Improvement on Nucleation and Crystal Growth of Perovskite
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破译 NH4PbI3 中间相以同时改善钙钛矿的成核和晶体生长
DOI：
10.1002/adfm.201701804
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发表时间：
2017-08-11
影响因子：
19
通讯作者：
Zhang, Yue
中科院分区：
文献类型：
--
作者：
Si, Haonan;Liao, Qingliang;Zhang, Yue
添加NH4I添加剂即可实现NH4PbI3基相变，以同时控制钙钛矿形核和晶体生长。在成核过程中，离子半径较小的NH4+优先扩散到[PbI6](4-)八面体层中形成NH4PbI3，弥补了CH3NH3I(MAI)沉淀的不足。NH4PbI3中间相的产生导致了额外的非均相成核位，减少了由于MA(+)的存在而产生的缺陷。在晶体生长过程中，MA(+)与NH4+之间的阳离子交换过程成功地延缓了晶体的生长，而不是MAS的直接进入。这样的NH4PbI3消耗过程减缓了晶体的生长，在降低缺陷密度的同时有效地提高了钙钛矿的质量。这两种效应的协同作用最终导致了高质量的钙钛矿结构，其颗粒尺寸增大，光致发光寿命延长，缺陷密度降低，载流子浓度增加，最终提高了光伏性能。此外，NH3作为副产物进一步促进了所提出的转化过程，即使没有任何后处理，也不会留下外部残留物。这种引入新的相变来同时控制成核和晶体生长过程的方法对于进一步致力于可预见的钙钛矿太阳能电池(PSCs)的发展具有普遍意义。
The NH4PbI3-based phase transformation is realized by simply adding NH4I additive, in order to simultaneously control perovskite nucleation and crystal growth. Regarding the nucleation process, the NH4+ with small ionic radius preferentially diffuses into the [PbI6](4-) octahedral layer to form NH4PbI3, which compensates the lack of CH3NH3I (MAI) precipitation. The generation of NH4PbI3 intermediate phase results in extra heterogeneous nucleation sites and reduces the defects derived from the absence of MA(+). Regarding the crystal growth process, the cation exchange process between MA(+) and NH4+, instead of the MAs directly entering, successfully retards the crystal growth. Such NH4PbI3 consumption process slows down the crystal growth, which effectively improves the perovskite quality with lowered defect density. The cooperation of these two effects eventually leads to the high-quality perovskite with enlarged grain size, prolonged photoluminescence lifetime, lowered defect density, and increased carrier concentration, as well as the finally enhanced photovoltaic performance. Moreover, NH3 as a byproduct further facilitates the proposed transformation process and no external residue remains even without any post-treatment. Such methodology of introducing a novel phase transformation to simultaneously control nucleation and crystal growth processes is of universal significance for further devotion in the foreseeable perovskite solar cells (PSCs) evolution.