THESIS
2017
xix, 101 pages : illustrations ; 30 cm
Abstract
Organic/Inorganic metal halide perovskite materials have triggered enormous attention for a
wide range of energy efficient and high-performance optoelectronic devices. However, their poor
stability poses a great challenge for further device fabrication and is a major bottle neck
challenge for practical applications. In this work, for the first time, three-dimensional, stable,
vertical CH
3NH
3PbI
3, CH
3NH
3SnI
3 and CsPbI
3 perovskite nanowires (NWs) are grown as a
result of the reaction between methylammonium iodide (MAI) or Cesium Iodide (CsI) with the
metal (Pb or Sn) in nano engineered porous alumina template (PAT) through a vapor–solid–solid
(VSS) process. Perovskite nanowire fabricated in nanoengineering can not only address
nanowire integration but also stability issue at the s...[
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Organic/Inorganic metal halide perovskite materials have triggered enormous attention for a
wide range of energy efficient and high-performance optoelectronic devices. However, their poor
stability poses a great challenge for further device fabrication and is a major bottle neck
challenge for practical applications. In this work, for the first time, three-dimensional, stable,
vertical CH
3NH
3PbI
3, CH
3NH
3SnI
3 and CsPbI
3 perovskite nanowires (NWs) are grown as a
result of the reaction between methylammonium iodide (MAI) or Cesium Iodide (CsI) with the
metal (Pb or Sn) in nano engineered porous alumina template (PAT) through a vapor–solid–solid
(VSS) process. Perovskite nanowire fabricated in nanoengineering can not only address
nanowire integration but also stability issue at the same time. Intriguingly, it was discovered that
as the nanowires are embedded in mechanically and chemically robust PAT, the material decay
process has been dramatically slowed down by up to 840 times, as compared with a planar thin
film. This significant improvement in stability can be attributed to the effective blockage of the
diffusion of water and oxygen molecules within the templates. These results clearly demonstrate
a new and alternative strategy to address the stability issue of perovskite materials which is the
major roadblock for high-performance optoelectronics. The optical characterization results
demonstrate that the as-synthesized NWs with an ultra-high nanostructure density can serve as
ideal candidates for optoelectronic devices, such as photodetectors. The reported growth approach here is highly versatile combining the merits of excellent controllability, cost-effectiveness
and tunability of material composition and physical properties. As a proof concept,
photodetector devices based on these as grown three types of stable, perovskite NWs array were
fabricated and the devices show decent and reasonable performance measures with specific
detectivity reaching to ~10
10 Jones.
Overall, this work demonstrates for the first-time a low cost, simple, novel and well controlled
guided growth of single crystalline organic/inorganic metallic halide perovskite NWs from the
chemical reaction between Pb/Sn metal precursor and MAI/CsI vapors by chemical vapor
deposition (CVD). This is a non-catalytic growth mechanism, which is distinctively different
with inorganic NWs growth in the past. These reported 3-D vertical perovskite NWs have
attractive properties of (1) enhanced stability, (2) single crystallinity (3) very high-density
4×10
8/cm
2, (3) periodic symmetry, (4) Low cost fabrication, and (5) tunable geometry of NWs.
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