Atmospheric pressure chemical vapor deposition of methylammonium bismuth iodide thin films. Issue 47 (20th November 2017)

• Record Type: Journal Article
• Authors: Chen, Xiao; Myung, Yoon; Thind, Arashdeep; Gao, Zhengning; Yin, Bo; Shen, Meikun; Cho, Sung Beom; Cheng, Peifu; Sadtler, Bryce; Mishra, Rohan; Banerjee, Parag
• Is Part Of: Journal of materials chemistry. Volume 5:Issue 47(2017)
• Page Start: 24728
• Page End: 24739
• Publication Date: 2017-11-20
• Subjects: Materials -- Research -- Periodicals; Chemistry, Analytic -- Periodicals; Environmental sciences -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c7ta06578g
• Languages: English
• ISSNs: 2050-7488

Abstract

Abstract : High quality methylammonium bismuth iodide films made using atmospheric pressure chemical vapor deposition. Abstract : We demonstrate the atmospheric pressure chemical vapor deposition of methyl ammonium bismuth iodide ((CH3 NH3 )3 Bi2 I9 or MA3 Bi2 I9 ) films. MA3 Bi2 I9 possesses an indirect optical bandgap of 1.80 eV and a room temperature excitonic peak at 511 nm. In contrast to recent reports, the films are n-type semiconductors with a room temperature carrier concentration of 3.36 × 10 18 cm −3 and a Hall mobility of 18 cm 2 V −1 s −1, which are superior to those of solution-processed, undoped films. The precursors used for the deposition are methylammonium iodide and bismuth iodide which are co-sublimated at 199 °C and 230 °C, respectively, in an Ar flow inside a tube furnace with a variable temperature profile. The substrate temperature is set at 160 °C, and dense polycrystalline films (∼775 nm thick) are deposited. Extensive characterization combined with first-principles density functional theory calculations unravels the synthesis–structure–property relationship in these films. The degradation of properties under ambient conditions results from film oxidation with a characteristic bi-exponential decay in resistivity, signifying a fast surface oxidation followed by a slower oxidation of the bulk.