Pub Date : 2012-06-03DOI: 10.1109/PVSC.2012.6318214
H. Sugimoto, H. Hiroi, N. Sakai, S. Muraoka, T. Katou
An efficiency of 8.6% on Cu2ZnSnS4 (CZTS) submodule is achieved by revising absorber formation and optimizing buffer layer thickness with the improved absorber. The CZTS submodule is fabricated by following process. Mo back electrode and metal precursor are deposited by vacuum-based processes. The CZTS absorber layer is formed through high-temperature annealing with sulfur containing gas. CdS buffer layer and ZnO window layer are then deposited by chemical bath deposition and metal-organic chemical vapor deposition, respectively. In this paper, we focus on the CZTS absorber uniformity and its thickness. Buffer thickness is also optimized. At first, performance of submodules with void-rich absorber and void-free absorber is investigated. Then, the impact of absorber thickness is investigated. We observe that thinner absorbers contribute to higher open circuit voltage whereas void-free absorbers contribute to higher fill factor. Over 8% submodule efficiency is achieved with void-free ultra-thin CZTS absorber layer with only 600 nm in thickness. Electron beam induced current (EBIC) mapping is performed to map out the distribution of current collection. The EBIC result clearly shows that the void-free and ultra-thin absorber has uniform and wide EBIC distribution. In addition, re-optimization of buffer layer thickness for the void-free and ultra-thin absorber further boosts the performance. We find that thinner CdS which lead to less absorption loss at short wavelength region works well with the void-free ultra-thin absorber. Further optimization will contribute to the development of lower cost and higher productivity CZTS fabrication process.
{"title":"Over 8% efficiency Cu2ZnSnS4 submodules with ultra-thin absorber","authors":"H. Sugimoto, H. Hiroi, N. Sakai, S. Muraoka, T. Katou","doi":"10.1109/PVSC.2012.6318214","DOIUrl":"https://doi.org/10.1109/PVSC.2012.6318214","url":null,"abstract":"An efficiency of 8.6% on Cu2ZnSnS4 (CZTS) submodule is achieved by revising absorber formation and optimizing buffer layer thickness with the improved absorber. The CZTS submodule is fabricated by following process. Mo back electrode and metal precursor are deposited by vacuum-based processes. The CZTS absorber layer is formed through high-temperature annealing with sulfur containing gas. CdS buffer layer and ZnO window layer are then deposited by chemical bath deposition and metal-organic chemical vapor deposition, respectively. In this paper, we focus on the CZTS absorber uniformity and its thickness. Buffer thickness is also optimized. At first, performance of submodules with void-rich absorber and void-free absorber is investigated. Then, the impact of absorber thickness is investigated. We observe that thinner absorbers contribute to higher open circuit voltage whereas void-free absorbers contribute to higher fill factor. Over 8% submodule efficiency is achieved with void-free ultra-thin CZTS absorber layer with only 600 nm in thickness. Electron beam induced current (EBIC) mapping is performed to map out the distribution of current collection. The EBIC result clearly shows that the void-free and ultra-thin absorber has uniform and wide EBIC distribution. In addition, re-optimization of buffer layer thickness for the void-free and ultra-thin absorber further boosts the performance. We find that thinner CdS which lead to less absorption loss at short wavelength region works well with the void-free ultra-thin absorber. Further optimization will contribute to the development of lower cost and higher productivity CZTS fabrication process.","PeriodicalId":6318,"journal":{"name":"2012 38th IEEE Photovoltaic Specialists Conference","volume":"28 1","pages":"002997-003000"},"PeriodicalIF":0.0,"publicationDate":"2012-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83664350","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 : 2012-06-03DOI: 10.1109/PVSC.2012.6318103
D. Alonso-Álvarez, D. Ross, K. McIntosh, B. Richards
In this work we address the performance of luminescence down shifting (LDS) layers in combination with cadmium sulfide/cadmium telluride (CdS/CdTe) solar cells as a function of the solar spectrum irradiance and power distribution, as would be the case in a real outdoor situation. To this purpose we have simulated the module efficiency when a CdS/CdTe mini-module is illuminated with a solar spectrum characteristic of different hours of the day and for five distinct days. Our results indicate that the LDS layer improves the conversion efficiency of the module in all scenarios (between 6 and 10%), where the improvement is most prominent at dawn and dusk (more than 20% on cloudy/summer days). The reason for this variation lies in the power distribution of the spectra, having a greater contribution of short-wavelength light in the morning or late in the afternoon. Under such blue-rich spectra the LDS layers operate very efficiently. Furthermore, we find that the relative efficiency improvement induced by an LDS layer has a roughly linear dependence with the average photon energy of the solar spectrum.
{"title":"Performance of luminescence down shifting for CdTe solar cells as a function of the incident solar spectrum","authors":"D. Alonso-Álvarez, D. Ross, K. McIntosh, B. Richards","doi":"10.1109/PVSC.2012.6318103","DOIUrl":"https://doi.org/10.1109/PVSC.2012.6318103","url":null,"abstract":"In this work we address the performance of luminescence down shifting (LDS) layers in combination with cadmium sulfide/cadmium telluride (CdS/CdTe) solar cells as a function of the solar spectrum irradiance and power distribution, as would be the case in a real outdoor situation. To this purpose we have simulated the module efficiency when a CdS/CdTe mini-module is illuminated with a solar spectrum characteristic of different hours of the day and for five distinct days. Our results indicate that the LDS layer improves the conversion efficiency of the module in all scenarios (between 6 and 10%), where the improvement is most prominent at dawn and dusk (more than 20% on cloudy/summer days). The reason for this variation lies in the power distribution of the spectra, having a greater contribution of short-wavelength light in the morning or late in the afternoon. Under such blue-rich spectra the LDS layers operate very efficiently. Furthermore, we find that the relative efficiency improvement induced by an LDS layer has a roughly linear dependence with the average photon energy of the solar spectrum.","PeriodicalId":6318,"journal":{"name":"2012 38th IEEE Photovoltaic Specialists Conference","volume":"37 1","pages":"002504-002508"},"PeriodicalIF":0.0,"publicationDate":"2012-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88457699","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 : 2012-06-03DOI: 10.1109/PVSC.2012.6317570
Jongwon Lee, S. Dahal, C. Honsberg
The efficiency limit of an intermediate band (IB) solar cell can be increased by a “tandem” configuration of multiple intermediate band devices. Thermodynamic models show that the efficiency of a two-stack tandem of IB devices achieves the efficiency of a six junction series connected solar cell. The efficiency of an IB in conjunction with a single or double stack tandem has similar efficiency advantages. Further, analysis of the materials which can be used to implement IB solar cells in a tandem configuration shows advantages relating to the ability to implement IB materials with quantum wells or quantum dots. For a single IB solar cell, a key difficulty is identifying materials for the barrier and the quantum well which have a small valence band offset and large conduction band offset (or the reverse). The use of an IB solar cell as the bottom solar cell of a tandem allows a larger range of materials with suitable barrier band gaps and a smaller ideal conduction band offset. A further theoretical advantage of such a structure is that it avoids the extremely low open circuit voltages achieved from pn junctions in low bandgap materials; for example, the thermodynamic optimum for a 6 junction tandem solar cell has its lowest bandgap below 0.4 eV. We present a thermodynamic model for IB hybrid tandem configurations which does not assume spectral selectivity among the different solar cells and predicts that a barrier/quantum dot structure can have an efficiency as high as 60 to 70 percent at 1000X blackbody radiation.
{"title":"Theoretical analysis for intermediate band and tandem hybrid solar cell materials","authors":"Jongwon Lee, S. Dahal, C. Honsberg","doi":"10.1109/PVSC.2012.6317570","DOIUrl":"https://doi.org/10.1109/PVSC.2012.6317570","url":null,"abstract":"The efficiency limit of an intermediate band (IB) solar cell can be increased by a “tandem” configuration of multiple intermediate band devices. Thermodynamic models show that the efficiency of a two-stack tandem of IB devices achieves the efficiency of a six junction series connected solar cell. The efficiency of an IB in conjunction with a single or double stack tandem has similar efficiency advantages. Further, analysis of the materials which can be used to implement IB solar cells in a tandem configuration shows advantages relating to the ability to implement IB materials with quantum wells or quantum dots. For a single IB solar cell, a key difficulty is identifying materials for the barrier and the quantum well which have a small valence band offset and large conduction band offset (or the reverse). The use of an IB solar cell as the bottom solar cell of a tandem allows a larger range of materials with suitable barrier band gaps and a smaller ideal conduction band offset. A further theoretical advantage of such a structure is that it avoids the extremely low open circuit voltages achieved from pn junctions in low bandgap materials; for example, the thermodynamic optimum for a 6 junction tandem solar cell has its lowest bandgap below 0.4 eV. We present a thermodynamic model for IB hybrid tandem configurations which does not assume spectral selectivity among the different solar cells and predicts that a barrier/quantum dot structure can have an efficiency as high as 60 to 70 percent at 1000X blackbody radiation.","PeriodicalId":6318,"journal":{"name":"2012 38th IEEE Photovoltaic Specialists Conference","volume":"51 1","pages":"000068-000072"},"PeriodicalIF":0.0,"publicationDate":"2012-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90972231","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 : 2012-06-03DOI: 10.1109/PVSC.2012.6317989
Tzu‐Ying Lin, Chia-Hsiang Chen, C. Lai
In this study, we have investigated the working pressure effect on the properties of molybdenum (Mo) films and how the Mo back contact affects the chalcopyrite Cu(In,Ga)Se2 (CIGS) films, which are prepared by one-step sputtering process. The properties of surface morphology, crystalline structure and residual stress are discussed. Mo films sputtered at low working pressure have dense structure with compressive stress, and become porous with tensile stress at high working pressure. In addition, the preferred orientation of following deposited CIGS film shows strong correlation with the residual stress of Mo back contact.
{"title":"Mo effect on one-step sputtering chalcopyrite CIGS thin films","authors":"Tzu‐Ying Lin, Chia-Hsiang Chen, C. Lai","doi":"10.1109/PVSC.2012.6317989","DOIUrl":"https://doi.org/10.1109/PVSC.2012.6317989","url":null,"abstract":"In this study, we have investigated the working pressure effect on the properties of molybdenum (Mo) films and how the Mo back contact affects the chalcopyrite Cu(In,Ga)Se2 (CIGS) films, which are prepared by one-step sputtering process. The properties of surface morphology, crystalline structure and residual stress are discussed. Mo films sputtered at low working pressure have dense structure with compressive stress, and become porous with tensile stress at high working pressure. In addition, the preferred orientation of following deposited CIGS film shows strong correlation with the residual stress of Mo back contact.","PeriodicalId":6318,"journal":{"name":"2012 38th IEEE Photovoltaic Specialists Conference","volume":"3 1","pages":"001999-002002"},"PeriodicalIF":0.0,"publicationDate":"2012-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89514051","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 : 2012-06-03DOI: 10.1109/PVSC.2012.6317754
Chia-Wei Chen, Xu dong Chen, K. Church, Haixin Yang, K. Tate, I. Cooper, A. Rohatgi
Screen printed low to medium concentrator silicon solar cells have potential to drive down the cost of PV since it replaces expensive semiconductor material by less expensive optics while maintaining high efficiency. However, the conventional screen-printed finger width is generally ≥100μm which limits the efficiency under higher concentration. In this paper, we report on the application of 50μm wide fingers fabricated by nScrypt non-contact direct printing technology to resolve this problem Two approaches were used to evaluate the merit of fine line extrusion printed fingers relative to normal screen-printed fingers. First approach involves keeping the metal coverage the same by increasing the number of lines, from 50 to 100, which lowers the series-resistance (Rs) and increases the FF. Second strategy involves keeping the Rs same by decreasing the number of lines, from 100 to 69, or reducing metal coverage which leads to higher Jsc. In this study, conventional screen-printed concentrator cells gave a peak efficiency of 19.2% at ~7 suns and 18.5% at 20 suns. The first strategy raised the peak efficiency to 19.7-20.0% in the range of 5 to 20 suns. The second approach to reducing metal coverage which keeping the same Rs raised the peak efficiency to 20.3% at ~7 suns which decreased gradually to 19.2% at 20 suns. Thus the use of 50μm wide lines can give 0.5 to 1.3% absolute efficiency enhancement in the range of 1-20 suns. These are among the most efficient metal paste printed low to medium concentrator solar silicon cells.
{"title":"High efficiency screen printed low-medium concentrator silicon solar cells with direct printed 50µm wide fingers","authors":"Chia-Wei Chen, Xu dong Chen, K. Church, Haixin Yang, K. Tate, I. Cooper, A. Rohatgi","doi":"10.1109/PVSC.2012.6317754","DOIUrl":"https://doi.org/10.1109/PVSC.2012.6317754","url":null,"abstract":"Screen printed low to medium concentrator silicon solar cells have potential to drive down the cost of PV since it replaces expensive semiconductor material by less expensive optics while maintaining high efficiency. However, the conventional screen-printed finger width is generally ≥100μm which limits the efficiency under higher concentration. In this paper, we report on the application of 50μm wide fingers fabricated by nScrypt non-contact direct printing technology to resolve this problem Two approaches were used to evaluate the merit of fine line extrusion printed fingers relative to normal screen-printed fingers. First approach involves keeping the metal coverage the same by increasing the number of lines, from 50 to 100, which lowers the series-resistance (Rs) and increases the FF. Second strategy involves keeping the Rs same by decreasing the number of lines, from 100 to 69, or reducing metal coverage which leads to higher Jsc. In this study, conventional screen-printed concentrator cells gave a peak efficiency of 19.2% at ~7 suns and 18.5% at 20 suns. The first strategy raised the peak efficiency to 19.7-20.0% in the range of 5 to 20 suns. The second approach to reducing metal coverage which keeping the same Rs raised the peak efficiency to 20.3% at ~7 suns which decreased gradually to 19.2% at 20 suns. Thus the use of 50μm wide lines can give 0.5 to 1.3% absolute efficiency enhancement in the range of 1-20 suns. These are among the most efficient metal paste printed low to medium concentrator solar silicon cells.","PeriodicalId":6318,"journal":{"name":"2012 38th IEEE Photovoltaic Specialists Conference","volume":"30 1","pages":"000928-000931"},"PeriodicalIF":0.0,"publicationDate":"2012-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89908817","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 : 2012-06-03DOI: 10.1109/PVSC.2012.6318249
Z. Bittner, D. Forbes, C. Bailey, S. Polly, M. Slocum, C. Kerestes, S. Hubbard
Heterojunction emitter InAs/GaAs quantum dot solar cells (QDSC) with an In0.48Ga0.52P (InGaP) n-type emitter and p-type GaAs base were fabricated along with homojunction nip solar cells in order to enable sub-cell polarity compatibility of InAs/GaAs QDSCs with current state-of-the-art monolithic InGaP/GaAs/Ge triple junction solar cells for space applications and to investigate potential dark current suppression effects and electronic field enhancement effects on carrier collection in InAs/GaAs QDSC. Quantum dot solar cells with one-Sun AM0 open circuit voltages greater than 970 mV were fabricated as compared to a 1.020 V heterojunction emitter `control' sample. Preliminary testing showed a reduction in short circuit current density from homojunction to heterojunction GaAs solar cells, primarily from changes in reflection and uncollected absorption in the InGaP emitter.
{"title":"Characterization of InGaP heterojunction emitter quantum dot solar cells","authors":"Z. Bittner, D. Forbes, C. Bailey, S. Polly, M. Slocum, C. Kerestes, S. Hubbard","doi":"10.1109/PVSC.2012.6318249","DOIUrl":"https://doi.org/10.1109/PVSC.2012.6318249","url":null,"abstract":"Heterojunction emitter InAs/GaAs quantum dot solar cells (QDSC) with an In0.48Ga0.52P (InGaP) n-type emitter and p-type GaAs base were fabricated along with homojunction nip solar cells in order to enable sub-cell polarity compatibility of InAs/GaAs QDSCs with current state-of-the-art monolithic InGaP/GaAs/Ge triple junction solar cells for space applications and to investigate potential dark current suppression effects and electronic field enhancement effects on carrier collection in InAs/GaAs QDSC. Quantum dot solar cells with one-Sun AM0 open circuit voltages greater than 970 mV were fabricated as compared to a 1.020 V heterojunction emitter `control' sample. Preliminary testing showed a reduction in short circuit current density from homojunction to heterojunction GaAs solar cells, primarily from changes in reflection and uncollected absorption in the InGaP emitter.","PeriodicalId":6318,"journal":{"name":"2012 38th IEEE Photovoltaic Specialists Conference","volume":"16 1","pages":"003158-003161"},"PeriodicalIF":0.0,"publicationDate":"2012-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90899387","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 : 2012-06-03DOI: 10.1109/PVSC.2012.6317826
M. Young, M. Benamara, H. Abu-Safe, Shui-Qing Yu, H. Naseem
Our progress with the creation of an a-Si:H/c-Si nanocomposite (NC) material for solar cells is given. The NC material is comprised of silicon nanowires (SiNW) embedded in a-Si:H. Discussion of how the nanowires are to be incorporated into a PV device is given. Scanning Electron Microscope (SEM) images show that the wires grow in a dense array with varied growth properties. Transmission Electron Microscope (TEM) images reveal that the nanowires contain crystalline Si. A conceptual overview of the fabrication process and predicted behaviors is given.
{"title":"A-Si:H/c-Si nanocomposite material for solar cells fabricated from PECVD","authors":"M. Young, M. Benamara, H. Abu-Safe, Shui-Qing Yu, H. Naseem","doi":"10.1109/PVSC.2012.6317826","DOIUrl":"https://doi.org/10.1109/PVSC.2012.6317826","url":null,"abstract":"Our progress with the creation of an a-Si:H/c-Si nanocomposite (NC) material for solar cells is given. The NC material is comprised of silicon nanowires (SiNW) embedded in a-Si:H. Discussion of how the nanowires are to be incorporated into a PV device is given. Scanning Electron Microscope (SEM) images show that the wires grow in a dense array with varied growth properties. Transmission Electron Microscope (TEM) images reveal that the nanowires contain crystalline Si. A conceptual overview of the fabrication process and predicted behaviors is given.","PeriodicalId":6318,"journal":{"name":"2012 38th IEEE Photovoltaic Specialists Conference","volume":"15 1","pages":"001236-001240"},"PeriodicalIF":0.0,"publicationDate":"2012-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90957786","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 : 2012-06-03DOI: 10.1109/PVSC.2012.6317849
Qi Zhang, Qun Li
Whether a crystalline Si PV cell in a module would fail in hotspot endurance test under partial shading condition is a practical question to many cell and module manufacturers. Answers to this question are associated with the reverse bias and elevated temperature across a partially shaded cell in a string of a module that is under illumination. This study reveals the reverse bias and temperature. It is found that the temperature has almost a linear relationship with the string length, and the reverse voltage is related to both cell Vpm and string length. The maximum reverse voltage and temperature under given string length and cell Vpm are summarized, which can serve as a pair of criteria to simulate the hot spot test condition to examine individual cell, study its hotspot properties. The elevated temperature can easily reach 130°C, when tested in a 24 cell string that is under short circuit condition during the test. And, the temperature can reach 150°C in a 30 cell string, which may cause permanent damage in module in such a test. Thus, it is cautioned that substantial increase in string length from 24 cells is not a realistic practice.
{"title":"Temperature and reverse voltage across a partially shaded Si PV cell under hot spot test condition","authors":"Qi Zhang, Qun Li","doi":"10.1109/PVSC.2012.6317849","DOIUrl":"https://doi.org/10.1109/PVSC.2012.6317849","url":null,"abstract":"Whether a crystalline Si PV cell in a module would fail in hotspot endurance test under partial shading condition is a practical question to many cell and module manufacturers. Answers to this question are associated with the reverse bias and elevated temperature across a partially shaded cell in a string of a module that is under illumination. This study reveals the reverse bias and temperature. It is found that the temperature has almost a linear relationship with the string length, and the reverse voltage is related to both cell Vpm and string length. The maximum reverse voltage and temperature under given string length and cell Vpm are summarized, which can serve as a pair of criteria to simulate the hot spot test condition to examine individual cell, study its hotspot properties. The elevated temperature can easily reach 130°C, when tested in a 24 cell string that is under short circuit condition during the test. And, the temperature can reach 150°C in a 30 cell string, which may cause permanent damage in module in such a test. Thus, it is cautioned that substantial increase in string length from 24 cells is not a realistic practice.","PeriodicalId":6318,"journal":{"name":"2012 38th IEEE Photovoltaic Specialists Conference","volume":"10 1","pages":"001344-001347"},"PeriodicalIF":0.0,"publicationDate":"2012-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89628526","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 : 2012-06-03DOI: 10.1109/PVSC.2012.6317574
B. Roberts, M. Boyd, P. Ku
Semi-transparent photovoltiacs are of interest for improving integration of solar energy harvesting with architecture. However, the competing requirements of optical transparency and efficient absorption of the incident spectrum severely limit performance. To address this tradeoff, we propose an angle selective organic photovoltaic window structure, structured such that normally incident light is transmitted to maintain window-quality transparency, while direct sunlight at an elevated angle is targeted for absorption. The localized surface plasmon resonance properties of metal nanorods are employed for angle and spectrally dependant scattering. The optical interference patterns arising when light propagates through subwavelength planar dielectric stacks are engineered to optimize the optical mode created by the metal scatterers via an evolutionary algorithm. We numerically model the transmission and absorption performance of a thin semi-transparent organic photovoltiac film under angled solar illumination to evaluate the potential for the proposed design. An optimized selective structure can maintain 70% optical transparency at normal incidence while improving total absorbed power by a factor of 2.3 vs. a lone semi-transparent cell of comparable transparency.
{"title":"Optical design of selectively scattering nanostructures for angle sensitive semi-transparent photovoltaics","authors":"B. Roberts, M. Boyd, P. Ku","doi":"10.1109/PVSC.2012.6317574","DOIUrl":"https://doi.org/10.1109/PVSC.2012.6317574","url":null,"abstract":"Semi-transparent photovoltiacs are of interest for improving integration of solar energy harvesting with architecture. However, the competing requirements of optical transparency and efficient absorption of the incident spectrum severely limit performance. To address this tradeoff, we propose an angle selective organic photovoltaic window structure, structured such that normally incident light is transmitted to maintain window-quality transparency, while direct sunlight at an elevated angle is targeted for absorption. The localized surface plasmon resonance properties of metal nanorods are employed for angle and spectrally dependant scattering. The optical interference patterns arising when light propagates through subwavelength planar dielectric stacks are engineered to optimize the optical mode created by the metal scatterers via an evolutionary algorithm. We numerically model the transmission and absorption performance of a thin semi-transparent organic photovoltiac film under angled solar illumination to evaluate the potential for the proposed design. An optimized selective structure can maintain 70% optical transparency at normal incidence while improving total absorbed power by a factor of 2.3 vs. a lone semi-transparent cell of comparable transparency.","PeriodicalId":6318,"journal":{"name":"2012 38th IEEE Photovoltaic Specialists Conference","volume":"42 1","pages":"000087-000091"},"PeriodicalIF":0.0,"publicationDate":"2012-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90398834","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 : 2012-06-03DOI: 10.1109/PVSC.2012.6317971
K. Tanabe, D. Guimard, D. Bordel, R. Morihara, M. Nishioka, Y. Arakawa
Quantum dot solar cells can potentially realize ultrahigh efficiencies in single p-n junction structures utilizing intermediate-level energy bands. However, so far most fabricated quantum dot solar cells have suffered from severe reduction of open-circuit voltage by incorporation of quantum dots resulting in significantly lower efficiencies than those without quantum dot. Here we fabricate a high-efficiency InAs/GaAs quantum dot solar cell. Our cell contains five layers of high-density (4 × 1010 cm-2 per layer) self-assembled InAs quantum dots grown by metalorganic chemical vapor deposition suppressing open-circuit-voltage degradation. We develop a dual-layer anti-reflection coating of optimum thicknesses. The resulting cell exhibits efficiencies of 18.7% under AM1.5G, 1 sun and 19.4% for 2 suns, the highest reported thus far, for any kind of quantum dot cell. Our high-efficiency demonstration in a cell grown by MOCVD is a strong encouragement towards the commercialization of quantum dot solar cells.
{"title":"High-efficiency InAs/GaAs quantum dot solar cells by MOCVD","authors":"K. Tanabe, D. Guimard, D. Bordel, R. Morihara, M. Nishioka, Y. Arakawa","doi":"10.1109/PVSC.2012.6317971","DOIUrl":"https://doi.org/10.1109/PVSC.2012.6317971","url":null,"abstract":"Quantum dot solar cells can potentially realize ultrahigh efficiencies in single p-n junction structures utilizing intermediate-level energy bands. However, so far most fabricated quantum dot solar cells have suffered from severe reduction of open-circuit voltage by incorporation of quantum dots resulting in significantly lower efficiencies than those without quantum dot. Here we fabricate a high-efficiency InAs/GaAs quantum dot solar cell. Our cell contains five layers of high-density (4 × 1010 cm-2 per layer) self-assembled InAs quantum dots grown by metalorganic chemical vapor deposition suppressing open-circuit-voltage degradation. We develop a dual-layer anti-reflection coating of optimum thicknesses. The resulting cell exhibits efficiencies of 18.7% under AM1.5G, 1 sun and 19.4% for 2 suns, the highest reported thus far, for any kind of quantum dot cell. Our high-efficiency demonstration in a cell grown by MOCVD is a strong encouragement towards the commercialization of quantum dot solar cells.","PeriodicalId":6318,"journal":{"name":"2012 38th IEEE Photovoltaic Specialists Conference","volume":"66 1","pages":"001929-001930"},"PeriodicalIF":0.0,"publicationDate":"2012-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90469236","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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