ORCID Profile
0000-0001-9059-1745
Current Organisation
Nanyang Technological University
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Publisher: AIP Publishing
Date: 04-12-2006
DOI: 10.1063/1.2402227
Abstract: The authors previously reported an unusual phenomenon of strain relaxation accompanied by a reduction in threading dislocation density (TDD) on a Si0.77Ge0.23 layer grown on top of alternating layers of Si0.77Ge0.23∕Si0.76Ge0.23C0.01 [Appl. Phys. Lett. 88, 041915 (2006)]. In this letter, the mechanism by which SiGeC domains, formed during annealing at 1000°C, assist in TDD annihilation process is further investigated. A g∙b analysis of transmission electron microscope images showed the formation of pure edge dislocations from the reaction of two 60° misfit dislocations, which glide and/or slip with the assistance of the localized interfacial strain of the SiGeC domains. TDD reduction in this structure is thus due to the annihilation of threading dislocation arms during misfit dislocation combination.
Publisher: American Chemical Society (ACS)
Date: 21-10-2020
Publisher: American Chemical Society (ACS)
Date: 20-10-2018
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 05-2018
Publisher: AIP Publishing
Date: 23-01-2006
DOI: 10.1063/1.2165283
Abstract: We report an observation of strain relaxation in lattice-mismatched heteroepitaxial Si1−xGex layers, accompanied by a reduction in threading dislocation density (TDD). This occurs on a Si0.77Ge0.23 layer grown on top of alternating layers of Si0.77Ge0.23∕Si0.76Ge0.23C0.01. The present scheme allows us to grow a high-quality 85% relaxed Si0.77Ge0.23 layer with a TDD of ∼104∕cm2. The high-resolution transmission electron microscope results showed the presence of Si1−x−yGexCy domains (with x⩽0.23 and y⩽0.01) after annealing at 1000°C. We infer that the formation of these domains assist the low TDD relaxation by releasing the epitaxial misfit strain as localized discrete strain and by blocking the propagation of misfit dislocations.
Publisher: Wiley
Date: 05-08-2020
Publisher: American Chemical Society (ACS)
Date: 23-10-2017
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C4TA05783J
Abstract: An aqueous spray-pyrolysis approach for synthesizing Cu(In,Ga)(S,Se) 2 thin film, which leads to 10.54% power conversion efficiency in solar cell, and shows ease of fabrication of films in large-scale at a much cheaper cost.
Publisher: American Chemical Society (ACS)
Date: 24-04-2014
DOI: 10.1021/JA501786S
Abstract: Single-phase Cu2ZnSnS4 (CZTS) is an essential prerequisite toward a high-efficiency thin-film solar cell device. Herein, the selective phase formation of single-phase CZTS nanoparticles by ligand control is reported. Surface-enhanced Raman scattering (SERS) spectroscopy is demonstrated for the first time as a characterization tool for nanoparticles to differentiate the mixed compositional phase (e.g., CZTS, CTS, and ZnS), which cannot be distinguished by X-ray diffraction. Due to the superior selectivity and sensitivity of SERS, the growth mechanism of CZTS nanoparticle formation by hot injection is revealed to involve three growth steps. First, it starts with nucleation of Cu(2-x)S nanoparticles, followed by diffusion of Sn(4+) into Cu(2-x)S nanoparticles to form the Cu3SnS4 (CTS) phase and diffusion of Zn(2+) into CTS nanoparticles to form the CZTS phase. In addition, it is revealed that single-phase CZTS nanoparticles can be obtained via balancing the rate of CTS phase formation and diffusion of Zn(2+) into the CTS phase. We demonstrate that this balance can be achieved by 1 mL of thiol with Cu(OAc)2, Sn(OAc)4, and Zn(acac)2 metal salts to synthesize the CZTS phase without the presence of a detectable binary/ternary phase with SERS.
Publisher: American Chemical Society (ACS)
Date: 18-07-2023
Publisher: The Electrochemical Society
Date: 2006
DOI: 10.1149/1.2168289
Publisher: American Chemical Society (ACS)
Date: 11-02-2016
DOI: 10.1021/ACS.NANOLETT.5B05124
Abstract: P-type transparent conducting films of nanocrystalline (CuS)x:(ZnS)1-x were synthesized by facile and low-cost chemical bath deposition. Wide angle X-ray scattering (WAXS) and high resolution transmission electron microscopy (HRTEM) were used to evaluate the nanocomposite structure, which consists of sub-5 nm crystallites of sphalerite ZnS and covellite CuS. Film transparency can be controlled by tuning the size of the nanocrystallites, which is achieved by adjusting the concentration of the complexing agent during growth optimal films have optical transmission above 70% in the visible range of the spectrum. The hole conductivity increases with the fraction of the covellite phase and can be as high as 1000 S cm(-1), which is higher than most reported p-type transparent materials and approaches that of n-type transparent materials such as indium tin oxide (ITO) and aluminum doped zinc oxide (AZO) synthesized at a similar temperature. Heterojunction p-(CuS)x:(ZnS)1-x/n-Si solar cells were fabricated with the nanocomposite film serving as a hole-selective contact. Under 1 sun illumination, an open circuit voltage of 535 mV was observed. This value compares favorably to other emerging heterojunction Si solar cells which use a low temperature process to fabricate the contact, such as single-walled carbon nanotube/Si (370-530 mV) and graphene/Si (360-552 mV).
Publisher: IOP Publishing
Date: 21-01-2015
DOI: 10.1088/0957-4484/26/6/064001
Abstract: Atomic layer deposition (ALD) provides a unique tool for the growth of thin films with excellent conformity and thickness control down to atomic levels. The application of ALD in energy research has received increasing attention in recent years. In this review, the versatility of ALD in solar cells will be discussed. This is specifically focused on the fabrication of nanostructured photoelectrodes, surface passivation, surface sensitization, and band-structure engineering of solar cell materials. Challenges and future directions of ALD in the applications of solar cells are also discussed.
Publisher: Wiley
Date: 18-09-2014
Abstract: Two new electron-rich molecules, 2,3,4,5-tetra[4,4'-bis(methoxyphenyl)aminophen-4"-yl]-thiophene (H111) and 4,4',5,5'-tetra[4,4'-bis(methoxyphenyl)aminophen-4"-yl]-2,2'-bithiophene (H112), which contain thiophene cores with arylamine side groups, are reported. When used as the hole-transporting material (HTM) in perovskite-based solar cell devices, power conversion efficiencies of up to 15.4% under AM 1.5G solar simulation were obtained. This is the highest efficiency achieved with HTMs not composed of 2,2',7,7'-tetrakis(N,N'-di-p-methoxyphenylamine)-9,9'-spirobifluorene (spiro-OMeTAD) and its isomers. Both HTMs, especially H111, have great potential to replace expensive spiro-OMeTAD given their much simpler and less expensive syntheses.
No related grants have been discovered for Lydia Helena Wong.