ORCID Profile
0000-0002-5644-8555
Current Organisation
UNSW Sydney
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Publisher: Elsevier BV
Date: 05-2023
Publisher: AIP Publishing
Date: 23-03-2020
DOI: 10.1063/1.5136289
Abstract: Environmentally friendly and earth abundant Cu2ZnSnS4 (CZTS) based thin films are potential absorbers for next generation photovoltaics. Their optical properties provide the option to be used as upper cells for Si based tandem solar cells, together with a similar structure to Si, triggering interest in investigation of CZTS/Si tandem cells. However, epitaxially growing CZTS on Si can be challenging. Here, we heteroepitaxially grow tetragonal Cu2ZnSnS4 (CZTS) thin films on single crystalline cubic Si (111) wafers with a 4° miscut by simple and low-cost radio frequency magnetron sputtering from a single target. The CZTS film displays a mirror-like surface with a surface roughness of 8.46 nm. The absorption coefficients of the epitaxial CZTS are over 104 cm−1 at 1.5 eV and 1.0 × 105 cm−1 at 2.1 eV. The bandgap is 1.45 eV, and the photoluminescence lifetime is 7.04 ns. Our results demonstrate the potential of the epitaxial CZTS films fabricated by sputtering on the Si substrate for application in CZTS/Si based tandem solar cells.
Publisher: Elsevier BV
Date: 08-2021
Publisher: Springer Science and Business Media LLC
Date: 2014
DOI: 10.1557/OPL.2014.271
Abstract: In this work, sulfurizing metal precursors prepared by magnetron sputtering was applied in Cu 2 ZnSnS 4 (CZTS) thin film fabrication. Three precursor structures, namely substrate/ Zn/(Cu& Sn), substrate/Zn/Cu/Sn/Cu and substrate/Zn/Sn/Cu, were compared for their synthesized CZTS film quality. It is notable that CZTS film made of the precursor structure of substrate/Zn/(Cu& Sn) has the best film quality with no obvious voids and biggest average grain size. When applying this precursor structure into device fabrication, a working CZTS device with an efficiency of 2.26% was made. The impact of metal precursors on the structural property of CZTS film were characterised by SEM, XRD, Raman and TEM. Thick MoS 2 interfacial layer (∼200nm) between absorber and back Mo contact and ZnS formed in the front and back absorber regions are the possible reasons limiting short-circuit current and fill factor of the cell.
Publisher: IEEE
Date: 14-06-2020
Publisher: IEEE
Date: 06-2017
Publisher: American Chemical Society (ACS)
Date: 07-10-2015
Abstract: Back contact modification plays an important role in improving energy conversion efficiency of Cu2ZnSnS4 (CZTS) thin film solar cells. In this paper, an ultrathin carbon layer is introduced on molybdenum (Mo)-coated soda lime glass (SLG) prior to the deposition of CZTS precursor to improve the back contact and therefore enhance CZTS solar cell efficiency. By introducing this layer, the short circuit current (Jsc) and device conversion efficiency increase for both nonvacuum (sol-gel) and vacuum (sputtering) methods. Specifically, for the sol-gel based process, Jsc increases from 13.60 to 16.96 mA/cm(2) and efficiency from 4.47% to 5.52%, while for the sputtering based process, Jsc increases from 17.50 to 20.50 mA/cm(2) and efficiency from 4.10% to 5.20%. Furthermore, introduction of this layer does not lead to any deterioration of either open circuit voltage (Voc) or fill factor (FF).
Publisher: Royal Society of Chemistry (RSC)
Date: 2018
DOI: 10.1039/C8CE00728D
Abstract: Improvements in charge carrier transport and equivalent photoluminescence were obtained for CuInS 2 nanoparticles with Ag-surface termination in photovoltaic devices.
Publisher: Elsevier BV
Date: 05-2011
Publisher: AIP Publishing
Date: 30-03-2015
DOI: 10.1063/1.4916994
Abstract: In this work, an industrially viable manufacturing process—rapid thermal annealing (RTA) of Molybdenum back contact is proposed and investigated to improve the performance of sputtered Cu2ZnSnS4 (CZTS) solar cells. The RTA process was found to facilitate Na diffusion from soda lime glass to Mo as well as CZTS and improve the crystallinity of the Mo film. Consequently, the surface morphology of the subsequently deposited CZTS absorbers is improved, which results in significant enhancement of open circuit voltage, short-circuit current density, fill factor, and conversion efficiency.
Publisher: Elsevier BV
Date: 06-2014
Publisher: Elsevier BV
Date: 2016
Publisher: American Chemical Society (ACS)
Date: 20-11-2019
Abstract: Electrically conductive polymer/rGO (reduced graphene oxide) films based on styrene and
Publisher: IEEE
Date: 06-2016
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2018
Publisher: Springer Science and Business Media LLC
Date: 07-10-2014
Publisher: AIP Publishing
Date: 28-04-2014
DOI: 10.1063/1.4873715
Abstract: The heterojunctions of different n-type buffers, i.e., CdS, Zn(O,S), and In2S3 on p-type Cu2ZnSnS4 (CZTS) were investigated using X-ray Photoelectron Spectroscopy (XPS) and Near Edge X-ray Absorption Fine Structure (NEXAFS) Measurements. The band alignment of the heterojunctions formed between CZTS and the buffer materials was carefully measured. The XPS data were used to determine the Valence Band Offsets (VBO) of different buffer/CZTS heterojunctions. The Conduction Band Offset (CBO) was calculated indirectly by XPS data and directly measured by NEXAFS characterization. The CBO of the CdS/CZTS heterojunction was found to be cliff-like with CBOXPS = −0.24 ± 0.10 eV and CBONEXAFS = −0.18 ± 0.10 eV, whereas those of Zn(O,S) and In2S3 were found to be spike-like with CBOXPS = 0.92 ± 0.10 eV and CBONEXAFS = 0.87 ± 0.10 eV for Zn(O,S)/CZTS and CBOXPS = 0.41 ± 0.10 eV for In2S3/CZTS, respectively. The CZTS photovoltaic device using the spike-like In2S3 buffer was found to yield a higher open circuit voltage (Voc) than that using the cliff-like CdS buffer. However, the CBO of In2S3/CZTS is slightly higher than the optimum level and thus acts to block the flow of light-generated electrons, significantly reducing the short circuit current (Jsc) and Fill Factor (FF) and thereby limiting the efficiency. Instead, the use of a hybrid buffer for optimization of band alignment is proposed.
Publisher: Elsevier BV
Date: 04-2018
Publisher: American Chemical Society (ACS)
Date: 02-07-2015
Abstract: A facile sol-gel and selenization process has been demonstrated to fabricate high-quality single-phase earth abundant kesterite Cu2ZnSn(S,Se)4 (CZTSSe) photovoltaic absorbers. The structure and band gap of the fabricated CZTSSe can be readily tuned by varying the [S]/([S] + [Se]) ratios via selenization condition control. The effects of [S]/([S] + [Se]) ratio on device performance have been presented. The best device shows 8.25% total area efficiency without antireflection coating. Low fill factor is the main limitation for the current device efficiency compared to record efficiency device due to high series resistance and interface recombination. By improving film uniformity, eliminating voids, and reducing the Mo(S,Se)2 interfacial layer, a further boost of the device efficiency is expected, enabling the proposed process for fabricating one of the most promising candidates for kesterite solar cells.
Publisher: Elsevier BV
Date: 09-2019
Publisher: AIP Publishing
Date: 27-01-2014
DOI: 10.1063/1.4863951
Abstract: In this work, 20 nm Ag is deposited on Mo coated soda lime glass prior to Cu2ZnSnS4 absorber deposition to improve the back contact and therefore enhance solar cell efficiency. This thin coating is found to inhibit the formation of SnS2, MoS2, and other defects especially voids at the back contact therefore, reduces the series resistance and recombination leading to substantially higher short circuit current density (JSC), fill factor, open circuit voltage (VOC), and efficiency in comparison to the controlled non-coating Mo, though the former results in lower material crystallinity.
Publisher: American Chemical Society (ACS)
Date: 21-11-2018
Abstract: The charge-storage kinetics of amorphous TiO
Publisher: IEEE
Date: 06-2016
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C5TA05813A
Abstract: By using sulfur atmosphere, Na compound, and suitable precursor composition, pure-sulfide Cu 2 ZnSnS 4 solar cells with 4.83% efficiency are fabricated by forming large grains from metastable wurtzite nanocrystals.
Publisher: American Chemical Society (ACS)
Date: 23-01-2020
Publisher: Springer Science and Business Media LLC
Date: 07-2020
DOI: 10.1557/MRE.2020.15
Publisher: IEEE
Date: 06-2019
Publisher: Elsevier BV
Date: 09-2020
Publisher: Royal Society of Chemistry (RSC)
Date: 2015
DOI: 10.1039/C5TC01750E
Abstract: Schematic representation of the CZTS absorber and device in this study.
Publisher: Elsevier BV
Date: 10-2014
Publisher: Elsevier BV
Date: 05-2015
Publisher: Elsevier BV
Date: 09-2017
Publisher: Elsevier BV
Date: 11-2016
Publisher: Elsevier BV
Date: 08-2018
Publisher: WIP
Date: 2013
Publisher: IEEE
Date: 06-2017
Publisher: IEEE
Date: 06-2017
Publisher: Wiley
Date: 21-10-2014
Publisher: Springer Science and Business Media LLC
Date: 2014
DOI: 10.1557/OPL.2014.405
Abstract: For structural investigation, highly (112) oriented tetragonal Cu 2 ZnSnS 4 (CZTS) thin films on hexagonal sapphire (0001) single crystal substrates were obtained by radio frequency (RF) magnetron sputtering. The influences of the deposition parameters, such as substrate temperature (T sub ) and working Ar pressure (P Ar ) on the chemical composition and structural properties of as deposited CZTS films were investigated. The film sputtered at 500°C has the only orientation of (112), also, it bears the best structural quality with pure CZTS phase and an estimated band gap of 1.51eV.
Publisher: The Electrochemical Society
Date: 2016
DOI: 10.1149/2.0441614JES
Publisher: Springer Science and Business Media LLC
Date: 2014
DOI: 10.1557/OPL.2014.208
Abstract: The focus of this work is on back contact improvement for sputtered CZTS thin film solar cells. Three methods have been investigated including a thin Ag coating, a thin ZnO coating on the Mo back contact and rapid thermal annealing of the back contact. All of these methods have been found to reduce defects such as voids as well as secondary phases at the back contact region and inhibit the formation of MoS 2 . Consequently all the mothods effectively enhances Voc, Jsc, FF and therefore efficiency significantly.
Publisher: Wiley
Date: 11-05-2021
DOI: 10.1002/PIP.3425
Abstract: This study investigated the laser‐induced damage arising from 266 and 532 nm laser ablation of SiN x films on alkaline textured Si surfaces with nanosecond and picosecond pulse durations using a combination of optical‐thermal simulations and measurements of carrier recombination current density. Simulations predict that the melting depth is limited to within 150 nm of the SiN x /Si surface after 266 nm ps laser irradiation due to the greater absorption in both the SiN x and Si resulting in more direct ablation, while temperatures exceeding the melting temperature of Si are predicted to extend up to 1000 nm into the Si substrate with 532 nm ps pulses leading primarily to spallation. Ablation of the SiN x by 266 nm ps irradiation is predicted to be more homogeneous on smaller sized pyramids due to the increased absorption of double‐bounce reflected light on the pyramid faces. This finding has implications for applications requiring uniform ablation of dielectrics on textured Si surfaces. Ablation of SiN x by the longer wavelength 532 nm ps pulses also increases carrier recombination compared to that incurred with 266 nm ps pulses due to the increased melting depth. Longer ns pulses result in less steep temperature gradients and, for 266 nm pulses, an increased melting depth compared to ps pulses. Consequently, shorter ps UV pulses are preferred for SiN x ablation on Si surfaces due to their reduced laser damage penetration, whereas the less steep temperature gradients resulting from ns 532 nm pulses are beneficial for laser doping to form selective emitters.
Publisher: Elsevier BV
Date: 07-2020
Publisher: IEEE
Date: 06-2016
Publisher: AIP Publishing
Date: 03-03-2014
DOI: 10.1063/1.4867093
Abstract: The heteroepitaxy of tetragonal Cu2ZnSnS4 (CZTS) thin films on hexagonal sapphire (0001) single crystal substrates is successfully obtained by radio frequency magnetron sputtering. The sputtered CZTS film has a mirror-like smooth surface with a root mean square roughness of about 5.44 nm. X-ray θ-2θ scans confirm that CZTS film is (112) oriented on sapphire with an out of plane arrangement of CZTS (112) ‖ sapphire (0001). X-ray Phi scan further illustrates an in plane ordering of CZTS [201¯] ‖ sapphire [21¯1¯0]. The high resolution transmission electron microscopy image of the interface region clearly shows that the CZTS thin film epitaxially grows on the sapphire (0001) substrate. The band gap of the film is found to be approximately 1.51 eV.
Publisher: IEEE
Date: 12-2012
Publisher: AIP Publishing
Date: 22-06-2015
DOI: 10.1063/1.4922992
Abstract: To explore the possibility of Cu2ZnSnS4 (CZTS)/Si based tandem solar cells, the heteroepitaxy of tetragonal Cu2ZnSnS4 thin films on single crystalline cubic Si (111) wafers with 4° miscut is obtained by molecular beam epitaxy. The X-ray θ-2θ scan and selected area diffraction patterns of the CZTS thin films and Si substrates, and the high resolution transmission electron microscopy image of the CZTS/Si interface region demonstrate that the CZTS thin films are epitaxially grown on the Si substrates. A CZTS/Si P-N junction is formed and shows photovoltaic responses, indicating the promising application of epitaxial CZTS thin films on Si.
Publisher: Elsevier BV
Date: 11-2018
Publisher: Wiley
Date: 05-2014
Publisher: Elsevier BV
Date: 11-2017
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 07-2018
Publisher: Wiley
Date: 31-03-2017
No related grants have been discovered for Ning Song.