Correlation of annealing time with crystal structure, composition, and electronic properties of CH3NH3PbI3−xClx mixed-halide perovskite films. Issue 1 (8th December 2016)

• Record Type: Journal Article
• Authors: Ralaiarisoa, Maryline; Busby, Yan; Frisch, Johannes; Salzmann, Ingo; Pireaux, Jean-Jacques; Koch, Norbert
• Is Part Of: Physical chemistry chemical physics. Volume 19:Issue 1(2017)
• Page Start: 828
• Page End: 836
• Publication Date: 2016-12-08
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c6cp06347k
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : Perovskite films composition evolves from a phase separation into uniform single phase with high preferred crystal orientation upon annealing. Abstract : Using 3D imaging with time-of-flight secondary ion mass spectrometry (ToF-SIMS) complemented by grazing-incidence X-ray diffraction (GIXRD), we spatially resolve changes in both the composition and structure of CH3 NH3 I3− x Cl x perovskite films on conducting polymer substrates at different annealing stages, in particular, before and after complete perovskite crystallization. The early stage of annealing is characterized by phase separation throughout the entire film into domains with perovskite and domains with a dominating chloride-rich phase. After sufficiently long annealing, one single perovskite phase of homogeneous composition on the (lateral) micrometer scale is observed, along with pronounced film texture. This composition evolution is accompanied by diffusion of chloride from the perovskite layer towards the conducting polymer substrate, and even accumulation there. Photoelectron spectroscopy analysis further shows that perovskite films become increasingly n-type with annealing time and upon full conversion, which correlates with the change of film composition. Our results accentuate the importance of chloride for the formation of crystalline and textured films, which are crucial for enhancing the PV performance of perovskite-based solar cells.