Almadori Yann, Moerman David, Martinez Jaume Llacer, Leclère Philippe, Grévin Benjamin
Université Grenoble Alpes, CNRS, CEA, INAC-SyMMES, 38000 Grenoble, France.
Laboratory for Chemistry of Novel Materials, Center of Innovation and Research in Materials & Polymers (CIRMAP), University of Mons, Place du Parc 20, B7000 Mons, Belgium.
Beilstein J Nanotechnol. 2018 Jun 7;9:1695-1704. doi: 10.3762/bjnano.9.161. eCollection 2018.
In this work, methylammonium lead tribromide (MAPbBr) single crystals are studied by noncontact atomic force microscopy (nc-AFM) and Kelvin probe force microscopy (KPFM). We demonstrate that the surface photovoltage and crystal photostriction can be simultaneously investigated by implementing a specific protocol based on the acquisition of the tip height and surface potential during illumination sequences. The obtained data confirm the existence of lattice expansion under illumination in MAPbBr and that negative photocarriers accumulate near the crystal surface due to band bending effects. Time-dependent changes of the surface potential occurring under illumination on the scale of a few seconds reveal the existence of slow ion-migration mechanisms. Lastly, photopotential decay at the sub-millisecond time scale related to the photocarrier lifetime is quantified by performing KPFM measurements under frequency-modulated illumination. Our multimodal approach provides a unique way to investigate the interplay between the charges and ionic species, the photocarrier-lattice coupling and the photocarrier dynamics in hybrid perovskites.
在这项工作中，通过非接触原子力显微镜（nc-AFM）和开尔文探针力显微镜（KPFM）对甲基溴化铅（MAPbBr）单晶进行了研究。我们证明，通过实施一种基于在光照序列期间获取针尖高度和表面电势的特定方案，可以同时研究表面光电压和晶体光致伸缩。所获得的数据证实了MAPbBr在光照下存在晶格膨胀，并且由于能带弯曲效应，负光载流子在晶体表面附近积累。在几秒钟的时间尺度上，光照下表面电势随时间的变化揭示了缓慢离子迁移机制的存在。最后，通过在调频光照下进行KPFM测量，对与光载流子寿命相关的亚毫秒时间尺度上的光势衰减进行了量化。我们的多模态方法为研究混合钙钛矿中电荷与离子物种之间的相互作用、光载流子-晶格耦合以及光载流子动力学提供了一种独特的方式。
