Examination Committee

Prof Woo Young LIM, ECON/HKUST (Chairperson)
Prof Zhiyong FAN, ECE/HKUST (Thesis Supervisor)
Prof Ni ZHAO, Department of Electronic Engineering, The Chinese University of Hong Kong (External Examiner)
Prof Kevin CHEN, ECE/HKUST
Prof George YUAN, ECE/HKUST
Prof Shihe YANG, CHEM/HKUST
 

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 perovskite nanowires (NWs) are grown as a result of the reaction between MAI or 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. 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 ~1010 Jones. These reported 3-D vertical perovskite NWs have attractive properties of (1) enhanced stability, (2) single crystallinity (3) very high-density 4×108/cm2, (3) periodic symmetry, (4) Low cost fabrication, and (5) tunable geometry of NWs.