Double Junction Amorphous Silicon Research Articles

The construction of a modified Typical Meteorological Year for photovoltaic modeling in India

Typical Meteorological Years (TMY) provide a basis for modeling solar photovoltaics. Their use, however, assumes continued historical norms inconsistent with climate change. Modifying TMYs with Regional Climate Models (RCMs) responds to this issue and has applications in renewable energy evaluations. This paper provides perspective on using modified TMYs for solar resource assessments, offers methodological improvements, and analyzes the impacts of insolation and irradiation changes on photovoltaic performance. For Ahmedabad, India, a TMY is constructed from Indian Meteorological Department measurements and modified with two Regional Climate Models - REGCM4 and REMO 2009. For each modified TMY and baseline, the performances of three photovoltaic technologies (monocrystalline, polycrystalline, and double-junction amorphous silicon) are considered for 2015–2050. Increases in ambient temperature are found to have small (<1.0%) but increasing negative impacts on monocrystalline and polycrystalline performance through 2050. A less significant positive trend (<0.1%) was observed for double-junction amorphous silicon. Insolation adjustments for REGCM4 were excluded after an error analysis. Insolation changes from REMO 2009 projected a 4% decrease in photovoltaic output by 2050, but should be considered cautiously given concerns over cloud modeling. A sensitivity analysis of monthly insolation modifications on photovoltaic performance revealed the relative impact of insolation changes in different months.

BIPV-temp: A demonstrative Building Integrated Photovoltaic installation

This paper presents the results of a demonstrative Building Integrated Photovoltaic (BIPV) installation in Lugano where five BiPV modules with different integration solutions (fully integrated as Double Glaze Units (DGUs) and ventilated), different inclinations (30° and 90°) and different technologies (double junction amorphous silicon (a-Si/a-Si) and crystalline silicon (c-Si)) were investigated. The paper aims at evaluating the impact of the operating cell temperature on the modules’ performance for different investigating cases. Two models were used to calculate the junctions’ temperatures of the modules under operation: the simplified Nominal Operating Temperature (NOCT) model and the Equivalent Cell Temperature (ECT). The first was used in a simplified version and the second was used for all modules, regardless of its limitations for thin film technologies. The two models agree well and give satisfactory results regardless of the inclination, integration solution or technology. The difference between the NOCT and ECT calculated average daily temperatures of the modules was found to be less than 5–6°C, with only one exception. As expected, fully integrated modules exhibit higher temperatures. In terms of performance, the integrated c-Si modules, regardless of their inclination, ranked lower – in terms of energy yield – than the integrated and ventilated a-Si/a-Si modules, for which the high operating temperatures proved to be beneficial. The inclination of 90° was found to be ideal for Lugano for both c-Si and a-Si/a-Si modules.

Full characterization of photovoltaic modules in real operating conditions: theoretical model, measurement method and results

AbstractThe photovoltaic (PV) system performance essentially depends on the modules response to five effects: spectral, reflection, temperature, irradiance, and nominal power variations. Providing a full characterization of modules behavior in terms of the impact of these effects on real operating conditions performance is very important both to compare different PV technologies and to choose the best technology for a specific site, position, and installation feature. In this work, a systematic approach is used. A theoretical model to calculate the performance ratio related to each effect is proposed. The model is used to compare and to explain the annual behavior of two different technologies: a multicrystalline silicon module (mc‐Si) and a double junction amorphous silicon module (a‐Si/DJ). The basic features of these modules performance are observed. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Artificial Leaf Goes Simpler and More Efficient for Solar Fuel Generation

Layer upon layer: Solar-to-fuel conversion through water splitting is among the most challenging and growing fields in present day science. Herein, a report is highlighted that successfully demonstrates an efficient photoanodic system utilizing simple and low-cost tungsten-doped bismuth vanadate on single- or double-junction amorphous silicon photovoltaic in a tandem configuration.

Comparative analysis of the outdoor performance of a dye solar cell mini‐panel for building integrated photovoltaics applications

AbstractNew generation photovoltaic (PV) devices such as polymer and dye sensitized solar cells (DSC) have now reached a more mature stage of development, and among their various applications, building integrated PVs seems to have the most promising future, especially for DSC devices. This new generation technology has attracted an increasing interest because of its low cost due to the use of cheap printable materials and simple manufacturing techniques, easy production, and relatively high efficiency. As for the more consolidated PV technologies, DSCs need to be tested in real operating conditions and their performance compared with other PV technologies to put into evidence the real potential. This work presents the results of a 3 months outdoor monitoring activity performed on a DSC mini‐panel made by the Dyepower Consortium, positioned on a south oriented vertical plane together with a double junction amorphous silicon (a‐Si) device and a multi‐crystalline silicon (m‐Si) device at the ESTER station of the University of Rome Tor Vergata. Good performance of the DSC mini‐panel has been observed for this particular configuration, where the DSC energy production compares favorably with that of a‐Si and m‐Si especially at high solar angles of incidence confirming the suitability of this technology for the integration into building facades. This assumption is confirmed by the energy produced per nominal watt‐peak for the duration of the measurement campaign by the DSC that is 12% higher than that by a‐Si and only 3% lower than that by m‐Si for these operating conditions. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Optimization of an i-a-SiOx:H absorber layer for thin film silicon solar cell applications

Wide gap, high quality hydrogenated intrinsic amorphous silicon (i-a-Si:H) alloy films are essentially required for multi-junction solar cells fabrication to enhance the open-circuit voltage (Voc) of the top cell. In this paper, intrinsic hydrogenated amorphous silicon oxide films (i-a-SiOx:H) have been prepared using a very high frequency plasma-enhanced chemical vapor deposition technique for use as an absorber layer of the top cell for double-junction amorphous silicon thin film solar cells. We studied the effects of the carbon dioxide (CO2) to silane (SiH4) ratio on the properties of the i-a-SiOx:H films and also optimized these films for application in a-SiOx:H/a-Si:H double-junction solar cells. The Voc of the a-SiOx:H/a-Si:H double-junction solar cells was higher than that of conventional a-Si:H/a-Si:H double-junction solar cells. Using an optimized deposition condition, a-SiOx:H/a-Si:H double-junction solar cell with an initial cell efficiency (η) of 10.2% was produced.

Comparative Analysis of Crystalline and Double-Junction Amorphous Silicon Modules Performance in Outdoor Conditions

The paper deals with an extensive photovoltaic (PV) modules monitoring activity carried out at the outdoor station ESTER (Solar Energy TEst and Research) of the University of Rome Tor Vergata, Italy. The purpose of the work was to evaluate and compare the performance of PV silicon modules of polycrystalline (poli-Si) and amorphous (a-Si) technologies during a medium-term outdoor exposure at optimized tilt angle, facing south. Two PV modules, one polycrystalline silicon and one double-junction amorphous silicon, have been exposed since May 2009 until Oct. 2010. A complete characterization of the weather conditions at the site during the test has been performed, and the most relevant parameters for the performance comparison of the two technologies have been derived. In order to compare different technologies and power productions, the energy yield (Y) and performance ratio (PR) for the two modules have been evaluated on a monthly and yearly basis. The typical seasonal trend of PR has been observed for the polycrystalline module, essentially due to the temperature influence on the module performance. For the a-Si module, instead, a degradation trend has been observed for the first months of operation. Subsequently, a significant recovery in the PR and energy production has been registered.

Influence of Average Photon Energy index on solar irradiance characteristics and outdoor performance of photovoltaic modules

ABSTRACTSolar spectral irradiance measurements on a routinely basis are relevant to study the influence of solar spectrum on the photovoltaic (PV) module performance, especially for thin film and third generation PV. Two spectroradiometers from EKO were added to the instrumentation available at the ESTER outdoor station of the University of Rome Tor Vergata. A detailed characterisation of the spectral irradiance at the site was carried on during more than 6 months of monitoring activity measuring spectral solar irradiance in the range 350–1700 nm with a time interval of 10 min on a horizontal plane. A wide variety of spectra were acquired in various weather conditions, and indications about the spectra behaviour on a daily and seasonal basis were obtained. Moreover, information about the effect of the weather conditions on the solar radiation spectral distribution were identified. The Average Photon Energy index was used as an indicator of the spectra characteristics. The same index was also used to evidence the solar spectrum influence on polycrystalline and double junction amorphous silicon PV modules. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Efficient Anode and Cathode Materials for Amorphous Silicon Solar Cell Driven all Solar Electrolysis of Water

AbstractFew non-noble metal based anode and cathode materials were investigated for all solar electrolysis of water to hydrogen and oxygen gases powered by double junction amorphous silicon (Dj-a-Si) solar cell under solar simulated light of 1 sun. The highest hydrogen generation current efficiency of 58.68% was obtained when Pt wire was used as a cathode with the non-noble metal based Ni-Co

In Search of Efficient Anode and Cathode Materials for Double Junction Amorphous Silicon Solar Cell Driven all Solar Electrolysis of Water to Hydrogen and Oxygen Gases

Few non-noble metal based anode and cathode materials were investigated for all solar electrolysis of water to hydrogen and oxygen gases powered by double junction amorphous silicon (Dj-a-Si) solar cell under solar simulated light of 1 sun. The highest hydrogen generation current efficiency of 58.68 % was obtained when Pt wire was used as a cathode with the non-noble metal based Ni-Co3O4 as an anode in the electrochemical cell. However, when Pt metal was replaced by a non-noble metal Ni the maximum hydrogen generation current efficiency of 51.28 % was observed. Comparable hydrogen generation current efficiencies were found when Ni-Co3O4 anode or thin RuO2 coated Ti metal anode (RuO2-Ti) was used in combination with Pt metal cathode. The percent solar to hydrogen conversion efficiencies (% STH) were found to be 8.66 % and 8.46 % for the Dj-a-Si solar cell driven electrolysis of water in the Ni-Co3O4||Pt and RuO2-Ti||Pt electrochemical cells respectively. For non-noble metal based electrochemical cell, Ni-Co3O4||Ni the % STH efficiency was found to be 7.57 %.

The effect of spectral variations on the performance parameters of single and double junction amorphous silicon solar cells

We present the results of an experimental investigation into the effects of spectral variations in a maritime climate on the performance parameters of single and double junction amorphous silicon solar cells. Such considerations are important for accurate modelling of system performance. It is shown that one can distinguish between two effects: a primary effect that results from variations in the total irradiance in the spectrally useful range of the device, and a secondary (mismatch) effect observed in double junction devices that is related to details of device structure. Results showing the impact on the short-circuit current, the current at the maximum-power-point, the fill factor and the overall efficiency are discussed.

Performance assessment of a 2 kWp grid-connected, building-integrated, amorphous silicon photovoltaic installation in Brazil

In September 1997 the first grid-connected, building-integrated photovoltaic (BIPV) installation in Brazil started operating in Florianópolis (27°S). The 2 kWp double-junction amorphous silicon PV system was retrofitted to the Solar Energy Laboratory's (LABSOLAR) building envelope, and connected through four commercial line-commutated inverters to the building's supply network. To demonstrate the architectural features of thin film PV technologies, both semitransparent and opaque modules were mounted on a north-facing, latitude-tilted overhang configuration. BIPV systems operating under the warmer conditions common in Brazil will typically experience relatively high operating temperatures, which suits the a-Si PV technology well. The installation is fully instrumented and is continuously monitored in order to allow the performance assessment of amorphous silicon PV operating at the prevailing conditions. This paper describes the design of the installation and presents system performance data from the first 18 months of operation. Copyright © 2000 John Wiley & Sons, Ltd.

Performance assessment of a 2 kWp grid‐connected, building‐integrated, amorphous silicon photovoltaic installation in Brazil

In September 1997 the first grid-connected, building-integrated photovoltaic (BIPV) installation in Brazil started operating in Florianópolis (27°S). The 2 kWp double-junction amorphous silicon PV system was retrofitted to the Solar Energy Laboratory's (LABSOLAR) building envelope, and connected through four commercial line-commutated inverters to the building's supply network. To demonstrate the architectural features of thin film PV technologies, both semitransparent and opaque modules were mounted on a north-facing, latitude-tilted overhang configuration. BIPV systems operating under the warmer conditions common in Brazil will typically experience relatively high operating temperatures, which suits the a-Si PV technology well. The installation is fully instrumented and is continuously monitored in order to allow the performance assessment of amorphous silicon PV operating at the prevailing conditions. This paper describes the design of the installation and presents system performance data from the first 18 months of operation. Copyright © 2000 John Wiley & Sons, Ltd.

Development of highly conductive n-type μc-Si:H films at low power for device applications

Highly conductive phosphorus-doped n-type hydrogenated microcrystalline silicon (μc-Si:H) films have been prepared by the usual (13.56 MHz) radio-frequency glow discharge of silane (SiH4), phosphine (PH3), and hydrogen (H2) in an ultrahigh-vacuum deposition system. The highest conductivity of the films obtained in this study is 100 S cm−1 after optimizing the hydrogen dilution ratio, chamber pressure, substrate temperature, and doping concentration of phosphorus. The formation of microcrystallinity in the material has been studied by transmission electron microscopy, x-ray-diffraction studies, and Raman spectroscopy. The volume fraction of microcrystallinity in these amorphous-microcrystalline mixed-phase materials has been estimated from Raman spectra. Sizes of the crystallites and volume fraction of microcrystallinity vary with hydrogen dilution, chamber pressure, and substrate temperature. The variations in the properties with deposition parameters have been explained in terms of the growth kinetics. The n-type μc-Si:H thin film, thus developed, has been applied in the first cell of a double-junction amorphous silicon solar cell. The prepared p-i-n–p-i-n stacked cell employing the n-type μc-Si:H film has exhibited appreciable improvement in open-circuit voltage, fill factor, and efficiency compared to the one with amorphous n layer in the inner n–p contact. Degradation of the cells prepared with and without μc-n layer has been studied.

Double-junction amorphous silicon-based solar cells with 11% stable efficiency

The performance of dual-band gap, double-junction amorphous silicon alloy-based solar cells in which the component cells have different degrees of current mismatch has been studied under annealed and light-soaked conditions. Using a profiled band gap amorphous silicon-germanium alloy in the bottom cell, a stabilized active-area efficiency of 11.16% has been achieved.

Advances in double-junction amorphous silicon photovoltaic modules

Large-area hydrogenated amorphous silicon solar cells with a two-stacked p-i-n junction tandem structure are practical solar cells with high conversion efficiency and reliability. We attained a total-area efficiency of 10.05% for a 30 cm × 40 cm tandem submodule. We found that the initial degradation of these tandem cells was about 15% on the initial value. Using these results, we discuss the feasibility of a stable 10% efficient a-Si photovoltaic module.