Atmospheric pressure chemical vapor deposition of methylammonium bismuth iodide thin films,Journal of Materials Chemistry A

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Atmospheric pressure chemical vapor deposition of methylammonium bismuth iodide thin films
Journal of Materials Chemistry A ( IF 10.7 ) Pub Date : 2017-10-31 00:00:00 , DOI: 10.1039/c7ta06578g
Xiao Chen _{1,

2,

3,

4} , Yoon Myung _{1,

2,

3,

4,

5} , Arashdeep Thind _{2,

3,

4,

6} , Zhengning Gao _{2,

3,

4,

6} , Bo Yin _{2,

3,

4,

6} , Meikun Shen _{2,

3,

4,

7} , Sung Beom Cho _{1,

2,

3,

4} , Peifu Cheng _{1,

2,

3,

4} , Bryce Sadtler _{2,

3,

4,

6,

7} , Rohan Mishra _{1,

2,

3,

4,

6} , Parag Banerjee _{1,

2,

3,

4,

6}

Affiliation

We demonstrate the atmospheric pressure chemical vapor deposition of methyl ammonium bismuth iodide ((CH₃NH₃)₃Bi₂I₉ or MA₃Bi₂I₉) films. MA₃Bi₂I₉ 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 × 10¹⁸ cm⁻³ and a Hall mobility of 18 cm² 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.

中文翻译：

甲基碘化铋铋薄膜的大气压化学气相沉积

我们证明了大气压化学气相沉积的甲基溴化铵（（CH ₃ NH ₃）₃ Bi ₂ I ₉或MA ₃ Bi ₂ I ₉）薄膜。MA ₃ Bi ₂ I ₉具有1.80 eV的间接光学带隙和511 nm处的室温激子峰。与最近的报道相反，这些膜是室温载流子浓度为3.36×10 ¹⁸ cm ^-3且霍尔迁移率为18 cm ² V ^-1 s ^-1的n型半导体。优于溶液处理的未掺杂薄膜。用于沉积的前体是甲基碘化铵和碘化铋，它们分别在具有可变温度曲线的管式炉内的Ar流中分别在199°C和230°C共同升华。基板温度设置为160°C，并沉积致密的多晶膜（约775 nm厚）。广泛的表征与第一性原理密度泛函理论计算相结合，揭示了这些薄膜的合成-结构-性质关系。在环境条件下性能下降是由于膜氧化导致电阻率出现双指数特征衰减，这意味着表面快速氧化，随后整体氧化较慢。

更新日期：2017-11-20

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