Hybrid perovskite solar cells: In situ investigation of solution-processed PbI2 reveals metastable precursors and a pathway to producing porous thin films. Issue 10 (17th April 2017)

• Record Type: Journal Article
• Authors: Barrit, Dounya; Sheikh, Arif D.; Munir, Rahim; Barbé, Jérémy M.; Li, Ruipeng; Smilgies, Detlef-M.; Amassian, Aram
• Is Part Of: Journal of materials research. Volume 32:Issue 10(2017)
• Page Start: 1899
• Page End: 1907
• Publication Date: 2017-04-17
• Subjects: hybrid perovskite solar cells, -- lead iodide, -- two-step conversion, -- solution processing, -- sol–gel, -- in situ grazing incidence wide angle X-ray scattering; Materials -- Research -- Periodicals; 620.1105
• DOI: 10.1557/jmr.2017.117
• Languages: English
• ISSNs: 0884-2914

Abstract

Abstract: Abstract : The successful and widely used two-step process of producing the hybrid organic-inorganic perovskite CH3 NH3 PbI3, consists of converting a solution deposited PbI2 film by reacting it with CH3 NH3 I. Here, we investigate the solidification of PbI2 films from a DMF solution by performing in situ grazing incidence wide angle X-ray scattering (GIWAXS) measurements. The measurements reveal an elaborate sol–gel process involving three PbI2 ⋅DMF solvate complexes—including disordered and ordered ones—prior to PbI2 formation. The ordered solvates appear to be metastable as they transform into the PbI2 phase in air within minutes without annealing. Morphological analysis of air-dried and annealed films reveals that the air-dried PbI2 is substantially more porous when the coating process produces one of the intermediate solvates, making this more suitable for subsequent conversion into the perovskite phase. The observation of metastable solvates on the pathway to PbI2 formation open up new opportunities for influencing the two-step conversion of metal halides into efficient light harvesting or emitting perovskite semiconductors.