Pub Date : 2009-06-07DOI: 10.1109/PVSC.2009.5411396
M. A. Matin, N. Amin, K. Sopian
Polycrystalline thin film CdTe shows great promise for efficient, low-cost photovoltaics (PV) cell. A numerical analysis was conducted utilizing AMPS simulator to explore the possibility of higher efficiency and stable CdS/CdTe cell among seven different cell structures with tin oxide (SnO2) and cadmium stannate (Cd2SnO4) as front contact layer, zinc oxide (ZnO) and zinc stannate (Zn2SnO4) as buffer layer and Ag or antimony telluride (Sb2Te3) with Mo as back contact material. It was found that the structure of CTO/ZTO/CdS/CdTe/Ag produced best efficiency over 17%. This analysis has also shown that Cd2SnO4 front contact, Zn2SnO4 buffer layer and Sb2Te3 back contact materials are suitable for high efficiency (≫15.5%) and stable CdTe based cells. Moreover, it was found that the cell normalized efficiency linearly decreased at the temperature gradient of −0.3%/°C.
{"title":"Investigation of different buffer layers, front and back contacts for CdS/CdTe PV from numerical analysis","authors":"M. A. Matin, N. Amin, K. Sopian","doi":"10.1109/PVSC.2009.5411396","DOIUrl":"https://doi.org/10.1109/PVSC.2009.5411396","url":null,"abstract":"Polycrystalline thin film CdTe shows great promise for efficient, low-cost photovoltaics (PV) cell. A numerical analysis was conducted utilizing AMPS simulator to explore the possibility of higher efficiency and stable CdS/CdTe cell among seven different cell structures with tin oxide (SnO<inf>2</inf>) and cadmium stannate (Cd<inf>2</inf>SnO<inf>4</inf>) as front contact layer, zinc oxide (ZnO) and zinc stannate (Zn<inf>2</inf>SnO<inf>4</inf>) as buffer layer and Ag or antimony telluride (Sb<inf>2</inf>Te<inf>3</inf>) with Mo as back contact material. It was found that the structure of CTO/ZTO/CdS/CdTe/Ag produced best efficiency over 17%. This analysis has also shown that Cd<inf>2</inf>SnO<inf>4</inf> front contact, Zn<inf>2</inf>SnO<inf>4</inf> buffer layer and Sb<inf>2</inf>Te<inf>3</inf> back contact materials are suitable for high efficiency (≫15.5%) and stable CdTe based cells. Moreover, it was found that the cell normalized efficiency linearly decreased at the temperature gradient of −0.3%/°C.","PeriodicalId":411472,"journal":{"name":"2009 34th IEEE Photovoltaic Specialists Conference (PVSC)","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115115953","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2009-06-07DOI: 10.1109/PVSC.2009.5411637
Larry Wang, A. Wang, R. Hockett
Impurities can adversely affect wafer yields and solar cell performance. Secondary Ion Mass Spectrometry (SIMS) is a very effective technique to quantitatively measure the elemental impurity concentrations in CIGS and CdTe based thin film solar cells. Na in CIGS: Na is an important composition element in CIGS based solar cells. SIMS depth profiles can provide the Na concentration distribution throughout the CIGS layer. The variation of compositions in different layers in CIGS presents a challenge for SIMS to accurately quantify Na concentrations, because SIMS quantification relies on reference materials with compositions that match the compositions of the different layers. In this study, we will present SIMS results of Na in CIGS films with different compositions, and solutions that can provide accurate Na quantification (within +−15%) of CIGS samples with unknown compositions. Impurities in CdTe/CdS: SIMS quantification at the CdTe/CdS interface and thin CdS layer is difficult due to change of materials. In this study, we will present solutions for accurate quantifications in CdTe/CdS.
{"title":"SIMS study of Na in CIGS and impurities in CdTe/CdS","authors":"Larry Wang, A. Wang, R. Hockett","doi":"10.1109/PVSC.2009.5411637","DOIUrl":"https://doi.org/10.1109/PVSC.2009.5411637","url":null,"abstract":"Impurities can adversely affect wafer yields and solar cell performance. Secondary Ion Mass Spectrometry (SIMS) is a very effective technique to quantitatively measure the elemental impurity concentrations in CIGS and CdTe based thin film solar cells. Na in CIGS: Na is an important composition element in CIGS based solar cells. SIMS depth profiles can provide the Na concentration distribution throughout the CIGS layer. The variation of compositions in different layers in CIGS presents a challenge for SIMS to accurately quantify Na concentrations, because SIMS quantification relies on reference materials with compositions that match the compositions of the different layers. In this study, we will present SIMS results of Na in CIGS films with different compositions, and solutions that can provide accurate Na quantification (within +−15%) of CIGS samples with unknown compositions. Impurities in CdTe/CdS: SIMS quantification at the CdTe/CdS interface and thin CdS layer is difficult due to change of materials. In this study, we will present solutions for accurate quantifications in CdTe/CdS.","PeriodicalId":411472,"journal":{"name":"2009 34th IEEE Photovoltaic Specialists Conference (PVSC)","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115355101","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2009-06-07DOI: 10.1109/PVSC.2009.5411770
H. Jin, K. Weber, B. Paudyal, C. Zhang
Negative charges were tunneled from Si surface into nitride film in the nitride/oxide/Si stacks by bias or corona charging. The tunneled charges appear to have linear relationship with the applied electrical field. A maximum negative charge density exists, when all K centers in nitride film are negative charged. At high bias condition, Si interface will take the risk of high energy electron damage. The damage is thermal unstable and can be annealed out at 300–400°C for very short time. Linear relationship is discovered with nitride thickness and threshold voltage, from which the electrical field strengths across nitride (3.4 MV/cm) and oxide (6 MV/cm) layers for tunneling were calculated. The tunneled charges are stable at room temperature, but will decay at elevated temperatures. At the cell operation conditions (around 90°C), 20% of the tunneled charges will disappear. At higher annealing conditions (350°C to 500°C), all tunneled charges vanish rapidly. Negative bias can also introduce negative charges around the top of the nitride layer through electrons injection. However, the negative charges are in very small amount and of little interest for PV applications.
{"title":"Introduction of negative charges in nitride for PV applications","authors":"H. Jin, K. Weber, B. Paudyal, C. Zhang","doi":"10.1109/PVSC.2009.5411770","DOIUrl":"https://doi.org/10.1109/PVSC.2009.5411770","url":null,"abstract":"Negative charges were tunneled from Si surface into nitride film in the nitride/oxide/Si stacks by bias or corona charging. The tunneled charges appear to have linear relationship with the applied electrical field. A maximum negative charge density exists, when all K centers in nitride film are negative charged. At high bias condition, Si interface will take the risk of high energy electron damage. The damage is thermal unstable and can be annealed out at 300–400°C for very short time. Linear relationship is discovered with nitride thickness and threshold voltage, from which the electrical field strengths across nitride (3.4 MV/cm) and oxide (6 MV/cm) layers for tunneling were calculated. The tunneled charges are stable at room temperature, but will decay at elevated temperatures. At the cell operation conditions (around 90°C), 20% of the tunneled charges will disappear. At higher annealing conditions (350°C to 500°C), all tunneled charges vanish rapidly. Negative bias can also introduce negative charges around the top of the nitride layer through electrons injection. However, the negative charges are in very small amount and of little interest for PV applications.","PeriodicalId":411472,"journal":{"name":"2009 34th IEEE Photovoltaic Specialists Conference (PVSC)","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121792225","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2009-06-07DOI: 10.1109/PVSC.2009.5411205
K.A.K. Chidvilas, Pramod Mani, S. Lyer, B. K. Rajbongshi, R. Gurunath
The fabricated devices reported here are based on small molecules. Device 2 performs better than device 1 under the same conditions. Further improvement s in device performance can be achieved by optimizing various layers. Also new molecules in the same family, with different functional groups, are being investigated for improved electrical and optical properties of the molecules.
{"title":"Bilayer organic solar cells based on imidazolin-5-one molecules","authors":"K.A.K. Chidvilas, Pramod Mani, S. Lyer, B. K. Rajbongshi, R. Gurunath","doi":"10.1109/PVSC.2009.5411205","DOIUrl":"https://doi.org/10.1109/PVSC.2009.5411205","url":null,"abstract":"The fabricated devices reported here are based on small molecules. Device 2 performs better than device 1 under the same conditions. Further improvement s in device performance can be achieved by optimizing various layers. Also new molecules in the same family, with different functional groups, are being investigated for improved electrical and optical properties of the molecules.","PeriodicalId":411472,"journal":{"name":"2009 34th IEEE Photovoltaic Specialists Conference (PVSC)","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121105064","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2009-06-07DOI: 10.1109/PVSC.2009.5411125
P. Altermatt, Yang Yang, T. Langer, A. Schenk, R. Brendel
We solve the Maxwell equations to quantify the amount of photo-generation in Si solar cells consisting of arrays of wires instead of bulk thin-films. Published transmission and reflectance measurements suggest that an array of Si wires absorbs sunlight very effectively due to strong diffraction and scattering. However, a detailed theoretical understanding and quantification of the actual photo-generation is only in its initial stage. In our simulations, the geometrical parameters of the wires are synthesized by means of cluster simulations. Applying the finite element method, we are able to compute randomly aligned wires within manageable time limits and affordable computer capacity. We show that Si wires have strong photonic properties. For example, our simulations surpass the Lambertian limit (for isotropically incident light) at λ = 1000 nm, as has been reported in many experiments.
{"title":"Simulation of optical properties of Si wire cells","authors":"P. Altermatt, Yang Yang, T. Langer, A. Schenk, R. Brendel","doi":"10.1109/PVSC.2009.5411125","DOIUrl":"https://doi.org/10.1109/PVSC.2009.5411125","url":null,"abstract":"We solve the Maxwell equations to quantify the amount of photo-generation in Si solar cells consisting of arrays of wires instead of bulk thin-films. Published transmission and reflectance measurements suggest that an array of Si wires absorbs sunlight very effectively due to strong diffraction and scattering. However, a detailed theoretical understanding and quantification of the actual photo-generation is only in its initial stage. In our simulations, the geometrical parameters of the wires are synthesized by means of cluster simulations. Applying the finite element method, we are able to compute randomly aligned wires within manageable time limits and affordable computer capacity. We show that Si wires have strong photonic properties. For example, our simulations surpass the Lambertian limit (for isotropically incident light) at λ = 1000 nm, as has been reported in many experiments.","PeriodicalId":411472,"journal":{"name":"2009 34th IEEE Photovoltaic Specialists Conference (PVSC)","volume":"56 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121235852","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2009-06-07DOI: 10.1109/PVSC.2009.5411329
Yifen Liu, Jaeyoun Kim
We designed an organic photovoltaic (PV) device with a gold (Au) grating top and a silver (Ag) bottom electrode. The Au grating will induce laterally propagating surface plasmon-polaritons (SPPs) along the interface between the PV active layer and the bottom Ag electrode. The SPPs enhance the light absorption length without increasing the PV active layer thickness.
{"title":"Absorption enhancement in thin film photovoltaic devices based on surface plasmon-polariton","authors":"Yifen Liu, Jaeyoun Kim","doi":"10.1109/PVSC.2009.5411329","DOIUrl":"https://doi.org/10.1109/PVSC.2009.5411329","url":null,"abstract":"We designed an organic photovoltaic (PV) device with a gold (Au) grating top and a silver (Ag) bottom electrode. The Au grating will induce laterally propagating surface plasmon-polaritons (SPPs) along the interface between the PV active layer and the bottom Ag electrode. The SPPs enhance the light absorption length without increasing the PV active layer thickness.","PeriodicalId":411472,"journal":{"name":"2009 34th IEEE Photovoltaic Specialists Conference (PVSC)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127444544","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2009-06-07DOI: 10.1109/PVSC.2009.5411607
S. Seyrling, S. Bucheler, A. Chirilă, J. Perrenoud, S. Wenger, T. Nakada, M. Gratzel, A. Tiwari
Due to the possibility of band gap engineering in Cu(In,Ga)Se2 (CIGS) absorbers and the spectral tunability of dye-sensitized solar cells (DSCs) with suitable choice of the sensitizer, this combination of solar cells could be ideal for the construction of dual junction photovoltaic devices. Factors for performance limitations of mechanically stacked tandem cells have been identified and alternative remedies are developed to overcome efficiency losses. Limiting factors of the efficiency have been determined. In a monolithical configuration, the issue of corrosion of the CIGS cell caused by exposure to the DSC electrolyte has been investigated.
{"title":"Development of multijunction thin film solar cells","authors":"S. Seyrling, S. Bucheler, A. Chirilă, J. Perrenoud, S. Wenger, T. Nakada, M. Gratzel, A. Tiwari","doi":"10.1109/PVSC.2009.5411607","DOIUrl":"https://doi.org/10.1109/PVSC.2009.5411607","url":null,"abstract":"Due to the possibility of band gap engineering in Cu(In,Ga)Se2 (CIGS) absorbers and the spectral tunability of dye-sensitized solar cells (DSCs) with suitable choice of the sensitizer, this combination of solar cells could be ideal for the construction of dual junction photovoltaic devices. Factors for performance limitations of mechanically stacked tandem cells have been identified and alternative remedies are developed to overcome efficiency losses. Limiting factors of the efficiency have been determined. In a monolithical configuration, the issue of corrosion of the CIGS cell caused by exposure to the DSC electrolyte has been investigated.","PeriodicalId":411472,"journal":{"name":"2009 34th IEEE Photovoltaic Specialists Conference (PVSC)","volume":"88 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125091107","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2009-06-07DOI: 10.1109/PVSC.2009.5411453
M. Hetzer, L. Brillson, D. Jensen
Nanoscale depth-resolved and cross sectional cathodoluminescence spectroscopy (DRCLS) provides correlations of local electronic and chemical structure with actual solar cell performance in sets of copper indium gallium diselenide (CIGS)/CdS/ZnO/ITO thin film solar cells. Local cross sectional and depth-dependent results throughout the various layers within the solar cells reveal local spatial variations in the CIGS band structure, even within the same grain. Band structure correlations to the efficiency, open circuit voltage, short circuit current performance characteristics of individual solar cells show evidence for alloying or intermixing between the CdS and ZnO layers forming alloys with higher band gap energies and degraded performance. Also, higher ZnO/ITO band edge intensities correspond to higher short circuit currents.
{"title":"Interfacial alloying and defect formation inside operational cigs solar cells","authors":"M. Hetzer, L. Brillson, D. Jensen","doi":"10.1109/PVSC.2009.5411453","DOIUrl":"https://doi.org/10.1109/PVSC.2009.5411453","url":null,"abstract":"Nanoscale depth-resolved and cross sectional cathodoluminescence spectroscopy (DRCLS) provides correlations of local electronic and chemical structure with actual solar cell performance in sets of copper indium gallium diselenide (CIGS)/CdS/ZnO/ITO thin film solar cells. Local cross sectional and depth-dependent results throughout the various layers within the solar cells reveal local spatial variations in the CIGS band structure, even within the same grain. Band structure correlations to the efficiency, open circuit voltage, short circuit current performance characteristics of individual solar cells show evidence for alloying or intermixing between the CdS and ZnO layers forming alloys with higher band gap energies and degraded performance. Also, higher ZnO/ITO band edge intensities correspond to higher short circuit currents.","PeriodicalId":411472,"journal":{"name":"2009 34th IEEE Photovoltaic Specialists Conference (PVSC)","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123670436","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2009-06-07DOI: 10.1109/PVSC.2009.5411520
Jian Li, Jie Chen, M. Sestak, Courtney Thornberry, R. Collins
Real time, in situ, and ex situ spectroscopic ellipsometry (SE) methods have been applied in systematic studies of the structure and optical properties of polycrystalline CdTe and CdS thin films deposited by rf magnetron sputtering. The goal of this ongoing research is to establish a basic understanding of the relationships between the physical and optical properties, including how the void fraction, grain size, strain, and temperature of measurement affect the complex dielectric function. This goal has been achieved through recent in situ and real time SE determinations of the structural evolution and dielectric functions of CdTe, CdS, and related alloys, in conjunction with in-depth analyses of the dielectric functions and their critical points. With a collection of parameterized dielectric functions and parameters linked to the physical properties, ex situ SE analysis of solar cell structures becomes possible for extracting not only thicknesses, but other useful physical properties as well.
{"title":"Spectroscopic ellipsometry studies of thin film CdTe and CdS: From dielectric functions to solar cell structures","authors":"Jian Li, Jie Chen, M. Sestak, Courtney Thornberry, R. Collins","doi":"10.1109/PVSC.2009.5411520","DOIUrl":"https://doi.org/10.1109/PVSC.2009.5411520","url":null,"abstract":"Real time, in situ, and ex situ spectroscopic ellipsometry (SE) methods have been applied in systematic studies of the structure and optical properties of polycrystalline CdTe and CdS thin films deposited by rf magnetron sputtering. The goal of this ongoing research is to establish a basic understanding of the relationships between the physical and optical properties, including how the void fraction, grain size, strain, and temperature of measurement affect the complex dielectric function. This goal has been achieved through recent in situ and real time SE determinations of the structural evolution and dielectric functions of CdTe, CdS, and related alloys, in conjunction with in-depth analyses of the dielectric functions and their critical points. With a collection of parameterized dielectric functions and parameters linked to the physical properties, ex situ SE analysis of solar cell structures becomes possible for extracting not only thicknesses, but other useful physical properties as well.","PeriodicalId":411472,"journal":{"name":"2009 34th IEEE Photovoltaic Specialists Conference (PVSC)","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123692748","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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