Zeguo Tang - Academia.edu (original) (raw)

Papers by Zeguo Tang

Nanotechnology, Apr 26, 2017

The solution-processed polycrystalline perovskite film contributes critically to the high photovo... more The solution-processed polycrystalline perovskite film contributes critically to the high photovoltaic performance of perovskite based solar cells (PSCs). The inevitable electronic trap states at grain boundaries and the intrinsic defects such as metallic lead (Pb0) and halide vacancies in perovskite film cause serious carrier recombination loss. Furthermore, the film can easily decompose into PbI2 in moisture atmosphere. Here, we introduce a simple strategy through a small increase in methylammonium iodide (CH3NH3I, MAI) molar proportion (5%) for perovskite fabrication in ambient air with a ~50% relative humidity. The analysis of morphology and crystallography demonstrates that excess MAI significantly promotes the grain growth without decomposition. X-ray photoemission spectroscopy (XPS) shows that no metallic Pb0 exists in the perovskite film and the I/Pb ratio is improved. The time-resolved photoluminescence (TRPL) measurement indicates an efficient suppression of non-radiative recombination in perovskite layer. As a result, the device yields improved power conversion efficiency (PCE) from 14.06% to 18.26% with reduced hysteresis and higher stability under AM1.5G illumination (100 mW/cm2). This work strongly provides a feasible and low-cost way to develop high-efficient PSCs in ambient air.

Nanotechnology, Jan 27, 2017

The solution-processed polycrystalline perovskite film contributes critically to the high photovo... more The solution-processed polycrystalline perovskite film contributes critically to the high photovoltaic performance of perovskite based solar cells (PSCs). The inevitable electronic trap states at grain boundaries and the intrinsic defects such as metallic lead (Pb0) and halide vacancies in perovskite film cause serious carrier recombination loss. Furthermore, the film can easily decompose into PbI2 in moisture atmosphere. Here, we introduce a simple strategy through a small increase in methylammonium iodide (CH3NH3I, MAI) molar proportion (5%) for perovskite fabrication in ambient air with a ~50% relative humidity. The analysis of morphology and crystallography demonstrates that excess MAI significantly promotes the grain growth without decomposition. X-ray photoemission spectroscopy (XPS) shows that no metallic Pb0 exists in the perovskite film and the I/Pb ratio is improved. The time-resolved photoluminescence (TRPL) measurement indicates an efficient suppression of non-radiative ...

EPJ Photovoltaics, 2012

Rapid thermal annealing of sputter-deposited ZnO and Al-doped ZnO (AZO) films with and without an... more Rapid thermal annealing of sputter-deposited ZnO and Al-doped ZnO (AZO) films with and without an amorphous silicon (a-Si) capping layer was investigated using a radio-frequency (rf) argon thermal plasma jet of argon at atmospheric pressure. The resistivity of bare ZnO films on glass decreased from 108 to 104–105 Ω cm at maximum surface temperatures Tmaxs above 650 °C, whereas the resistivity increased from 10-4 to 10-3–10-2Ω cm for bare AZO films. On the other hand, the resistivity of AZO films with a 30-nm-thick a-Si capping layer remained below 10-4Ω cm, even after TPJ annealing at a Tmax of 825 °C. The film crystallization of both AZO and a-Si layers was promoted without the formation of an intermixing layer. Additionally, the crystallization of phosphorous- and boron-doped a-Si layers at the sample surface was promoted, compared to that of intrinsic a-Si under the identical plasma annealing conditions. The TPJ annealing of n+-a-Si/textured AZO was applied for single junction n-...

Japanese Journal of Applied Physics, 2014

ABSTRACT

Chemistry of Materials, 2016

Solar Energy Materials and Solar Cells, 2015

Abstract Reaction path for fabrication of Cu 2 SnSe 3 (CTSe) film by selenization of Cu–Sn precur... more Abstract Reaction path for fabrication of Cu 2 SnSe 3 (CTSe) film by selenization of Cu–Sn precursor was investigated via in-situ X-ray diffraction (XRD) as well as glazing incident XRD (GIXRD) measurements. Cross-sectional scanning electron microscopy (SEM)-energy dispersive spectrometry (EDS) and transmission electron microscope (TEM) analyses revealed the element and phase distribution along the depth direction. Based on these results, a proposed growth model was concluded below: first, the Se atoms from evaporation source reacted with Cu and Sn atoms to produce Cu 2− x Se and SnSe 2 phases. Noticeably, resulting film presented bilayer feature with Cu 2− x Se located at the surface and SnSe 2 located at bottom. Second, CTSe phase formed at the interface of Cu 2− x Se and SnSe 2 as the increasing temperature. The Cu 2− x Se was depleted by Sn-related secondary phases when the Cu/Sn ratio was smaller than 1.72. The secondary phases of SnSe 2 and SnSe were coexisted with CTSe phase independent of Cu/Sn ratio in metallic precursor, which was attributed to the weak diffusion ability of Sn and Sn-related secondary phases in the CTSe film. The origins for high carrier concentration in CTSe films were ascribed to the Cu 2− x Se and intrinsic acceptor concentration and effective approach to reduce the value was explored. An attempt of solar cell with CTSe as absorber was performed and photocurrent of 9.9 mA/cm 2 was detected.

physica status solidi (a), 2015

Japanese Journal of Applied Physics, 2014

ABSTRACT We fabricated Cu2ZnSn(S,Se)4 (CZTSSe) solar cells with (Zn,Mg)O buffer layers as an alte... more ABSTRACT We fabricated Cu2ZnSn(S,Se)4 (CZTSSe) solar cells with (Zn,Mg)O buffer layers as an alternative to the CdS buffer layer for the improvement of cell performance, where the (Zn,Mg)O layers are deposited by sputtering. However, the solar cell efficiency decreased with the (Zn,Mg)O layer as compared with the CdS layer. Photoluminescence measurements indicated that the damage near the surface of the CZTSSe absorber was induced by the sputtering. To suppress the damage, a 10-nm-thick CdS layer was deposited on the absorber before sputtering. As a result, the efficiency achieved with the (Zn,Mg)O layer was the same as that with the CdS layer. To further improve the efficiency of the cell with the (Zn,Mg)O layer, it is necessary to eliminate sputtering damage. In addition, the conduction band offset of the (Zn,Mg)O/CZTSSe interface is controllable by varying the Mg content. Therefore, the (Zn,Mg)O buffer layer can be suitable against a large-band-gap CZTSSe absorber.

Progress in Photovoltaics: Research and Applications, 2015

Thin Solid Films, 2015

ABSTRACT Cu2ZnSn(S,Se)4 (CZTSSe) solar cells were fabricated with an annealing treatment before t... more ABSTRACT Cu2ZnSn(S,Se)4 (CZTSSe) solar cells were fabricated with an annealing treatment before the deposition of buffer layers to improve their photovoltaic performance. The CZTSSe absorbers were produced by sulfurization and selenization of metallic precursors. The efficiency of the solar cells increased from 5.5% without the annealing treatment to 8.8% with the annealing treatment at a temperature of 200 °C before buffer layer fabrication. Photoluminescence (PL) measurements revealed that the density of defects in the CZTSSe absorber that acted as non-radiative recombination centers decreased with the annealing treatment. The PL peak intensity exhibited a linear relationship with the open circuit voltage and the fill factor. In addition, the carrier density and hole mobility of the CZTSSe absorbers, which were respectively investigated by capacitance–voltage and Hall effect measurements, increased with the annealing treatment, thus improving cell performance.

Journal of Alloys and Compounds, 2014

Applied Physics Letters, 2012

ABSTRACT We demonstrate a highly efficient hybrid crystalline silicon (c-Si) based photovoltaic d... more ABSTRACT We demonstrate a highly efficient hybrid crystalline silicon (c-Si) based photovoltaic devices with hole-transporting transparent conductive poly-(3,4-ethlenedioxythiophene):poly(styrenesufonic acid) (PEDOT:PSS) films, incorporating a Zonyl fluorosurfactant as an additive, compared to non additive devices. The usage of a 0.1% Zonly treated PEDOT:PSS improved the adhesion of precursor solution on hydrophobic c-Si wafer without any oxidation process. The average power conversion efficiency η value was 10.8%-11.3%, which was superior to those of non-treated devices. Consequently, c-Si/Zonyl-treated PEDOT:PSS heterojunction devices exhibited the highest η of 11.34%. The Zonyl-treated soluble PEDOT:PSS composite is promising as a hole-transporting transparent conducting layer for c-Si/organic photovoltaic applications.

Applied Surface Science, 2010

Nanotechnology, Apr 26, 2017

The solution-processed polycrystalline perovskite film contributes critically to the high photovo... more The solution-processed polycrystalline perovskite film contributes critically to the high photovoltaic performance of perovskite based solar cells (PSCs). The inevitable electronic trap states at grain boundaries and the intrinsic defects such as metallic lead (Pb0) and halide vacancies in perovskite film cause serious carrier recombination loss. Furthermore, the film can easily decompose into PbI2 in moisture atmosphere. Here, we introduce a simple strategy through a small increase in methylammonium iodide (CH3NH3I, MAI) molar proportion (5%) for perovskite fabrication in ambient air with a ~50% relative humidity. The analysis of morphology and crystallography demonstrates that excess MAI significantly promotes the grain growth without decomposition. X-ray photoemission spectroscopy (XPS) shows that no metallic Pb0 exists in the perovskite film and the I/Pb ratio is improved. The time-resolved photoluminescence (TRPL) measurement indicates an efficient suppression of non-radiative recombination in perovskite layer. As a result, the device yields improved power conversion efficiency (PCE) from 14.06% to 18.26% with reduced hysteresis and higher stability under AM1.5G illumination (100 mW/cm2). This work strongly provides a feasible and low-cost way to develop high-efficient PSCs in ambient air.

Nanotechnology, Jan 27, 2017

The solution-processed polycrystalline perovskite film contributes critically to the high photovo... more The solution-processed polycrystalline perovskite film contributes critically to the high photovoltaic performance of perovskite based solar cells (PSCs). The inevitable electronic trap states at grain boundaries and the intrinsic defects such as metallic lead (Pb0) and halide vacancies in perovskite film cause serious carrier recombination loss. Furthermore, the film can easily decompose into PbI2 in moisture atmosphere. Here, we introduce a simple strategy through a small increase in methylammonium iodide (CH3NH3I, MAI) molar proportion (5%) for perovskite fabrication in ambient air with a ~50% relative humidity. The analysis of morphology and crystallography demonstrates that excess MAI significantly promotes the grain growth without decomposition. X-ray photoemission spectroscopy (XPS) shows that no metallic Pb0 exists in the perovskite film and the I/Pb ratio is improved. The time-resolved photoluminescence (TRPL) measurement indicates an efficient suppression of non-radiative ...

EPJ Photovoltaics, 2012

Rapid thermal annealing of sputter-deposited ZnO and Al-doped ZnO (AZO) films with and without an... more Rapid thermal annealing of sputter-deposited ZnO and Al-doped ZnO (AZO) films with and without an amorphous silicon (a-Si) capping layer was investigated using a radio-frequency (rf) argon thermal plasma jet of argon at atmospheric pressure. The resistivity of bare ZnO films on glass decreased from 108 to 104–105 Ω cm at maximum surface temperatures Tmaxs above 650 °C, whereas the resistivity increased from 10-4 to 10-3–10-2Ω cm for bare AZO films. On the other hand, the resistivity of AZO films with a 30-nm-thick a-Si capping layer remained below 10-4Ω cm, even after TPJ annealing at a Tmax of 825 °C. The film crystallization of both AZO and a-Si layers was promoted without the formation of an intermixing layer. Additionally, the crystallization of phosphorous- and boron-doped a-Si layers at the sample surface was promoted, compared to that of intrinsic a-Si under the identical plasma annealing conditions. The TPJ annealing of n+-a-Si/textured AZO was applied for single junction n-...

Japanese Journal of Applied Physics, 2014

ABSTRACT

Chemistry of Materials, 2016

Solar Energy Materials and Solar Cells, 2015

Abstract Reaction path for fabrication of Cu 2 SnSe 3 (CTSe) film by selenization of Cu–Sn precur... more Abstract Reaction path for fabrication of Cu 2 SnSe 3 (CTSe) film by selenization of Cu–Sn precursor was investigated via in-situ X-ray diffraction (XRD) as well as glazing incident XRD (GIXRD) measurements. Cross-sectional scanning electron microscopy (SEM)-energy dispersive spectrometry (EDS) and transmission electron microscope (TEM) analyses revealed the element and phase distribution along the depth direction. Based on these results, a proposed growth model was concluded below: first, the Se atoms from evaporation source reacted with Cu and Sn atoms to produce Cu 2− x Se and SnSe 2 phases. Noticeably, resulting film presented bilayer feature with Cu 2− x Se located at the surface and SnSe 2 located at bottom. Second, CTSe phase formed at the interface of Cu 2− x Se and SnSe 2 as the increasing temperature. The Cu 2− x Se was depleted by Sn-related secondary phases when the Cu/Sn ratio was smaller than 1.72. The secondary phases of SnSe 2 and SnSe were coexisted with CTSe phase independent of Cu/Sn ratio in metallic precursor, which was attributed to the weak diffusion ability of Sn and Sn-related secondary phases in the CTSe film. The origins for high carrier concentration in CTSe films were ascribed to the Cu 2− x Se and intrinsic acceptor concentration and effective approach to reduce the value was explored. An attempt of solar cell with CTSe as absorber was performed and photocurrent of 9.9 mA/cm 2 was detected.

physica status solidi (a), 2015

Japanese Journal of Applied Physics, 2014

ABSTRACT We fabricated Cu2ZnSn(S,Se)4 (CZTSSe) solar cells with (Zn,Mg)O buffer layers as an alte... more ABSTRACT We fabricated Cu2ZnSn(S,Se)4 (CZTSSe) solar cells with (Zn,Mg)O buffer layers as an alternative to the CdS buffer layer for the improvement of cell performance, where the (Zn,Mg)O layers are deposited by sputtering. However, the solar cell efficiency decreased with the (Zn,Mg)O layer as compared with the CdS layer. Photoluminescence measurements indicated that the damage near the surface of the CZTSSe absorber was induced by the sputtering. To suppress the damage, a 10-nm-thick CdS layer was deposited on the absorber before sputtering. As a result, the efficiency achieved with the (Zn,Mg)O layer was the same as that with the CdS layer. To further improve the efficiency of the cell with the (Zn,Mg)O layer, it is necessary to eliminate sputtering damage. In addition, the conduction band offset of the (Zn,Mg)O/CZTSSe interface is controllable by varying the Mg content. Therefore, the (Zn,Mg)O buffer layer can be suitable against a large-band-gap CZTSSe absorber.

Progress in Photovoltaics: Research and Applications, 2015

Thin Solid Films, 2015

ABSTRACT Cu2ZnSn(S,Se)4 (CZTSSe) solar cells were fabricated with an annealing treatment before t... more ABSTRACT Cu2ZnSn(S,Se)4 (CZTSSe) solar cells were fabricated with an annealing treatment before the deposition of buffer layers to improve their photovoltaic performance. The CZTSSe absorbers were produced by sulfurization and selenization of metallic precursors. The efficiency of the solar cells increased from 5.5% without the annealing treatment to 8.8% with the annealing treatment at a temperature of 200 °C before buffer layer fabrication. Photoluminescence (PL) measurements revealed that the density of defects in the CZTSSe absorber that acted as non-radiative recombination centers decreased with the annealing treatment. The PL peak intensity exhibited a linear relationship with the open circuit voltage and the fill factor. In addition, the carrier density and hole mobility of the CZTSSe absorbers, which were respectively investigated by capacitance–voltage and Hall effect measurements, increased with the annealing treatment, thus improving cell performance.

Journal of Alloys and Compounds, 2014

Applied Physics Letters, 2012

ABSTRACT We demonstrate a highly efficient hybrid crystalline silicon (c-Si) based photovoltaic d... more ABSTRACT We demonstrate a highly efficient hybrid crystalline silicon (c-Si) based photovoltaic devices with hole-transporting transparent conductive poly-(3,4-ethlenedioxythiophene):poly(styrenesufonic acid) (PEDOT:PSS) films, incorporating a Zonyl fluorosurfactant as an additive, compared to non additive devices. The usage of a 0.1% Zonly treated PEDOT:PSS improved the adhesion of precursor solution on hydrophobic c-Si wafer without any oxidation process. The average power conversion efficiency η value was 10.8%-11.3%, which was superior to those of non-treated devices. Consequently, c-Si/Zonyl-treated PEDOT:PSS heterojunction devices exhibited the highest η of 11.34%. The Zonyl-treated soluble PEDOT:PSS composite is promising as a hole-transporting transparent conducting layer for c-Si/organic photovoltaic applications.

Applied Surface Science, 2010