Schueleraktion Solare Zukunft auf der Solar Energy 2002, Berlin, 13-15 Juni 2002 Abschlussbericht

This project was intended to intensify environmental education, specifically in the field of renewable energy sources, in German schools and to improve the communication competence of German pupils. Selected activities were presented at the SolarEnergy 2002 in Berlin. (orig.)Das Projekt Schueleraktion Solare Zukunft hatte das Ziel, Umweltbildungsaspekte, speziell des Bereiches Erneuerbarer Energien, an deutschen Schulen zu intensivieren und auf diesem Sektor zur Staerkung der Kommunikationskompetenz von Schuelern beizutragen. Das Projekt gab ausgewaehlten Schuelern die Moeglichkeit, sich mit ihren Arbeiten auf der Berliner Weltmesse fuer Erneuerbare Energien - SolarEnergy 2002 - zu praesentieren und mit Vertretern von Wissenschaft, Politik und Wirtschaft in Kontakt zu treten. Damit war es ein weiteres Ziel, ein besseres Verstaendnis der Theorie durch angewandten Praxisbezug zu foerdern. Ausgangspunkt fuer die Ueberlegungen, ein Projekt des Namens Schueleraktion Solare Zukunft auf der Weltmesse SolarEnergy 2002 durchzufuehren, waren mehrere Punkte. (orig.)SIGLEAvailable from TIB Hannover: F04B298 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDeutsche Bundesstiftung Umwelt, Osnabrueck (Germany)DEGerman

Novel back contact silicon solar cells designed for very high efficiencies and low-cost mass production

To make photovoltaics an economic source of energy the efficiency of industrial crystalline silicon solar cells has to be drastically increased without complicating the fabrication process. Solar cells with both contacts on the rear side are promising candidates for further increasing cell and module efficiency as well as significantly simplifying module assembly. A new generation of back contact silicon solar cells, based on the self-aligned mask and photolithography-free Oblique-Evaporation-of- Contact (OECO) technology is introduced. The outstanding high-efficiency features and the low-cost production features including the advantages for thin wafers and bifacial operation of the so called BACK-OECO solar cells are outlined. Simulation studies based on the experimental experience with front-contacted OECO cells are revealing that these new devices have the potential to achieve efficiencies up to 22% under industrial conditions using Cz grown silicon. Custom-made high-throughput processing equipment recently completed by us for the crucial fabrication steps including back surface grooving, oblique metal evaporation and high quality low temperature surface passivation is described.SIGLEAvailable from: http://www.isfh.de/institut/publika/NewOrleans.htm / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Highly efficient industrial-size silicon solar cells based on innovative OECO technology Paper

The obliquely evaporated contact (OECO) solar cell structure recently developed at ISFH allows to reach efficiencies of 20% and above by applying an industrially feasible manufacturing process. In this paper, the key technologies for the fabrication of OECO-type solar cells: (i) mechanical grinding for surface structuring, (ii) oblique vacuum evaporation for metallization, (iii) remote plasma-enhanced chemical vapour deposition (RPECVD) of silicon nitride (SiNx) for surface passivation and (iv) conductive adhesive technology for cell interconnection are discussed in detail. Furthermore, the latest results of industrial-size OECO solar cells are presented.Available from: http://www.isfh.de/institut/publika/muenchen.htm / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

EN

The outstanding surface passivation properties of remote plasma-enhanced chemical vapour deposited (RPECVD) silicon nitride (SiN_x) films developed at ISFH clearly correlate with Si/N-ratio. Since the physical reason of this correlation is still unknown, this work presents a comprehensive study of the relationship between film composition and surface passivation quality of RPECVD SiN_x on p-type crystalline silicon. The films were characterised by photoconductance decay measurements, infrared spectroscopy, nuclear reaction analysis and capacitance voltage curves recorded in the dark and - for the first time - under illumination using Al/SiN_x/p-Si metal-nitride-silicon capacitors. As a key result clear correlations were found between the surface recombination velocity and the concentration of N and Si dangling bonds in the volume of SiN_x films featuring a refractive index of 1.9 and 2.1, respectively.SIGLEAvailable from: http://www.isfh.de/institut/publika/muenchen.htm / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Hoechsteffiziente multikristalline Silicium-Solarzellen mit industrie-relevantem Herstellungsverfahren Schlussbericht

The manufacturing of highly efficient silicon solar cells can be simplified drastically by introduction of a low-temperature passivation for both surfaces as well as a mechanical structuring of the front surface in conjunction with a mask-free shallow angle evaporation of the front side metallisation. Using single crystalline silicon, major progresses were made at ISFH in this area. The aim of this research project is to apply the highly efficient solar cell structures developed at ISFH (pn- as well as advanced metal insulator semiconductor inversion-layer (MIS-IL) silicon solar cells) for the first time to multicrystalline silicon from BAYER (BAYSIX "r"e"g"i"s"t"e"r"e"d, RGS) and from RWE Schott Solar (EFG). Large area multicrystalline silicon solar cells with highest efficiencies shall be manufactured using industrially relevant production processes. The efficiencies obtained due to the novel ISFH solar cell concepts are 18.1% on multicrystalline BAYSIC "r"e"g"i"s"t"e"r"e"d material. In a close co-operation with the companies BAYER and RWE Schott Solar a significant improvement of the photovoltaic economy shall be achieved with an innovative, worldwide leading product developed in Germany, possibly resulting in an important stimulation of the PV industry. In the course of the project 10 #chi# 10 cm"2 solar cells on single crystalline silicon with efficiencies up to 20% could be manufactured at ISFH due to the transfer of important insights to this material. These were international peak values for industrially manufacturable solar cells with such dimensions. This outstanding result suggested to transfer this so called OECO (Obliquely Evaporated COntacts) technique - developed at ISFH for easily and economically manufacturing highest efficient silicon solar cells - from the research scale into laboratory pilot line production state. Due to an increase of the financial resources the solar cell production facilities at ISFH were expanded so that there were enough solar cells to manufacture several different, industrially relevant PV modules with highest efficiencies. Of prime importance was the development of the OECO solar cell technology together with an adapted module technique up to a valuable, industrially feasible commercial product. (orig.)Available from TIB Hannover: F04B2116 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Umwelt, Naturschutz und Reaktorsicherheit, Bonn (Germany)DEGerman

Entwicklung einer CdTe/CdS Duennschicht-Solarzelle Schlussbericht

The focus was on the development and optimisation of the close-spaced sublimation process in an inline coating plant for production of stable high-efficiency CdS/CdTe solar wafers. An inline plant was to be constructed by ANTEC GmbH and ISFH. Film layers were to be optimised, and investigations were to show whether processing of single films is possible without breaking the vacuum, e.g. for etching. The results were to be used directly by ANTEC GmbH. An efficiency of 14 percent and an idle voltage of about 850 V were to be achieved with a film thickness of 2 #mu#m. To achieve these goals, the following project stages were envisaged: 1. Replacement of the expensive window material ITO by a less costly material. 2. Higher stability of the back contact by using appropriate intermediate layers. 3. Alternative activation processes other than the conventional CdCl_2 activation. 4. Investigation of the effects of the activation step on the electric properties of the sample.Die uebergreifende Aufgabenstellung des Projektes war die Entwicklung und Optimierung des Close-spaced-Sublimation verfahrens in einer Inline-Beschichtungsanlage fuer die Herstellung stabiler und hocheffizienter CdS/CdTe Duennschichtsolarzellen. Mit dem Wissen der ANTEC GmbH sollte zusammen mit dem ISFH eine Inline-Anlage konzipiert und gebaut werden. Die fuer die Solarzelle notwendigen Einzelschichten sollten in dem Inline-Prozess optimiert werden. Es sollte ermittelt werden, ob eine Prozessierung der Einzelschichten ohne Brechen des Vakuums, z.B. fuer einen Aetzschritt, moeglich ist. Die erzielten Ergebnisse sollen direkt der ANTEC GmbH zufliessen. In dem Projekt wurde als Endziel ein Wirkungsgrad der CdTe/CdS-Duennschichtsolarzelle von 14% und eine Erhoehung der Leerlaufspannung auf Werte um 850 mV angestrebt. Gleichzeitig sollte die CdTe-Schichtdicke auf 2 #mu#m vermindert werden. Um dieses Gesamtziel zu erreichen, sollen folgende Teilaufgaben bearbeitet werden: 1) Das teuere Fenstermaterial ITO soll durch ein kostenguenstiges Material ersetzt werden. 2) Die Stabilitaet des Rueckkontaktes soll durch geeignete Rueckkontaktzwischenschichten erhoeht werden. 3) Alternative Aktivierungsprozesse zur herkoemmlichen CdCl_2-Aktivierung sollen erprobt werden. 4) Die Auswirkung des Aktivierungsschrittes auf das elektrische Verhalten der Probe soll mit geeigneten Verfahren untersucht werden. (orig.)Available from TIB Hannover: F03B576+a / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEBundesministerium fuer Bildung und Forschung, Berlin (Germany)DEGerman

Effective reduction of the metastable defect concentration in boron-doped Czochralski silicon for solar cells

Different approaches to reduce the light-induced degradation of Czochralski silicon (Cz-Si) solar cells are investigated. In the first part of this paper the very promising possibility of using overcompensated oxygen-rich n-type silicon with residual boron as solar cell substrate material is demonstrated. Stable bulk carrier lifetimes in the millisecond range are achievable in this material. The second part of this work deals with new technological approaches to reduce the concentration of the metastable defect responsible for the light-induced carrier lifetime degradation in boron-doped Czochralski silicon. A permanent reduction of the defect concentration by a factor of up to 3.5 is achieved with an optimized emitter diffusion process at 850 C in a conventional quartz tube furnace using fast ramping conditions. Long-term annealing treatments performed at low temperature (450 C) are shown to reduce the metastable defect concentration by a factor of up to 3.3 and, at the same time, lead to the formation of thermal donors (TDs). These results are in good agreement with our new defect model which assumes a fast-diffusing oxygen dimer as part of the Cz-specific defect.Available from: http://www.isfh.de/institut/publika/NewOrleans.htm / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Formation and annihilation of the metastable defect in boron-doped Czochralski silicon

This paper aims at elucidating the physical mechanism responsible for the light-induced efficiency degradation of solar cells fabricated on boron-doped Czochralski silicon (Cz-Si). Lifetime measurements on Cz-Si wafers at defined injection levels show that the concentration of the light-induced metastable defect increases linearly with the substitutional boron concentration. Moreover, a quadratic increase with the interstitial oxygen density is measured. The defect generation rate is examined as a function of temperature at constant illumination intensity. Our measurements clearly prove that the defect generation process is thermally activated with a relatively low energy barrier of E_g_e_n= 0.4 eV. The activation energy of the defect annihilation process is determined to be independent of the boron doping level at E_a_n_n= 1.8 eV. On the basis of our experimental findings, we introduce a new defect reaction model. In this model, fast-diffusing oxygen dimers O2i are captured by substitutional boron Bs to form a complex B_s-O2i, acting as highly effective recombination center. Promising new strategies for an effective reduction of the light degradation are derived from the proposed model.Available from: http://www.isfh.de/institut/publika/NewOrleans.htm / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Qualitaetssicherung mit Informations- und Beratungskampagne bei der Realisierung einer Solarsiedlung Abschlussbericht

A solar housing project of 68 single family dwellings is constructed on the southern slope of a hill in the town of Emmerthal. High thermal insulation, active and passive solar energy use, and a two-stage heat pump process will reduce carbon dioxide emissions by 50 percent as compared to the current standard. All buildings are designed to consume 30 percent less than the heating energy consumption required by the WSVO '95. 60 percent of the hot water will consumed will be heated by solar energy. Consulting and information of the builder-owners as well as quality assurance measures during construction will serve to ensure that these goals are met and will also provide a documentation of the energy balance of the housing project.SIGLEAvailable from TIB Hannover: F02B1703 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDeutsche Bundesstiftung Umwelt, Osnabrueck (Germany)DEGerman

Formation and annihilation of the metastable defect in boron-doped Czochralski silicon

This paper aims at elucidating the physical mechanism responsible for the light-induced efficiency degradation of solar cells fabricated on boron-doped Czochralski silicon (Cz-Si). Lifetime measurements on Cz-Si wafers at defined injection levels show that the concentration of the light-induced metastable defect increases linearly with the substitutional boron concentration. Moreover, a quadratic increase with the interstitial oxygen density is measured. The defect generation rate is examined as a function of temperature at constant illumination intensity. Our measurements clearly prove that the defect generation process is thermally activated with a relatively low energy barrier of E_g_e_n= 0.4 eV. The activation energy of the defect annihilation process is determined to be independent of the boron doping level at E_a_n_n= 1.8 eV. On the basis of our experimental findings, we introduce a new defect reaction model. In this model, fast-diffusing oxygen dimers O2i are captured by substitutional boron Bs to form a complex B_s-O2i, acting as highly effective recombination center. Promising new strategies for an effective reduction of the light degradation are derived from the proposed model.Available from: <a href=http://www.isfh.de/institut/publika/NewOrleans.htm target=NewWindow>http://www.isfh.de/institut/publika/NewOrleans.htm</a> / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman