Design of inductors and modeling of relevant field intensity

Transcription

1 3. Growth of shaped Si single crystals (FZ) Design of inductors and modeling of relevant field intensity Main cut Schematic of inductor for large square FZ crystals z-component of the field intensity for a square inductor with 4 cuts

2 3. Growth of shaped Si single crystals (FZ) 9

3 3. Growth of shaped Si single crystals (FZ) 4-cut inductor used to grow round 100 mm FZ-crystals corresponding square melting lines at the lower surface of the feed rod

4 3. Growth of shaped Si single crystals (FZ) Results of 3D numerical simulations The maximum electro-magnetic coupling occurs corresponding to the four inductor cuts. The crystal-melt interface results deformed with a square symmetry The cut geometry determines the high and sharpness of the power maxima, i.e. the sharpness of the crystal edges Size and length of the cuts are vital in determining a stable process. If the cuts are not appropriate the melt will overflow and the growth will fail This may cause problems in the first phase of the growth as the cuts are designed as a function of the crystal main body Rotation is necessary in the crystal cone

5 3. Growth of shaped Si single crystals (FZ) Molten zone Undulated interface Square silicon crystal Shape of the S/L interface in the FZ process with no rotation

6 3. Growth of shaped Si single crystals (FZ) Quasi-square wafer Dopant distribution patterns detected by LPS (lateral photovoltage scanning)

7 4. Deposition of polycrystalline Si on glass Motivation Criteria for low cost PV technology: large scale production low cost substrates low processing temperatures Growth of Si on glass from solution Crystalline silicon on glass: hope for low cost solar cells

8 4. Deposition of polycrystalline Si on glass Amorpous-Liquidus-Crystalline-Process Travelling solvent droplets 1 µm 4 µm

9 4. Deposition of polycrystalline Si on glass T Concentration and temperature in isothermal conditions µ c-si µ µ a-si z C l,a Natural convection = f(c,t) Surface convection = f(c,t) C l,cr v Estimate of the latent heat Estimate of the driving force a c µ T cr c-si Glas T a α-si

10 4. Deposition of polycrystalline Si on glass Formation of continous crystalline layer on glass 1µm 1µm 10µm 10µm

11 4. Deposition of polycrystalline Si on glass Test of crystallinity 10µm

12 4. Deposition of polycrystalline Si on glass Test of crystallinity 10µm

13 4. Deposition of polycrystalline Si on glass Test of crystallinity 10µm To be published in Thin Solid Films

14 4. Deposition of polycrystalline Si on glass c-si T=300 C glass Further processing v a-si 400nm T=450 C glass glass 400nm 10µm 1 µm

15 4. Deposition of polycrystalline Si on glass Metallic solution Growth of the epilayer by TDM Glas top Si-feed stock Graphite crucible bottom T top bottom t

16 4. Deposition of polycrystalline Si on glass Polycrystalline Si films: surface aspect Very good adhesion

17 5. Conclusions Overview of the activity on solar Si at IKZ Use of traveling magnetic fields as tool for improving MC material Use of traveling magnetic field to achieve extremely low radial gradients in Cz growth => exploit the surface kinetic to get faceted (shaped) crystals Dislocation-free single crystalline Si with square cross-section by FZ with special inductors and no rotation Two step process for the deposition of thick Si layers on glass

18 Acknowledgement MC-Silicon and shaped Cz silicon under magnetic fields P. Rudolph, Ch. Frank-Rotsch, F. Kießling, B. Lux, M. Czupalla, O. Root + Dept. Simulation & Characterization and technical staff Partners: Steremat, Auteam, ETP Uni Hannover, WIAS, IHP-BTU Joint Lab, Calisolar, Schott Solar Wafers Sponsorship: Technologiestiftung Berlin, Zukunftsagentur Brandenburg Shaped FZ silicon H. Riemann, A. Lüdge, J. Rost, B. Hallmann-Seifert Partners : PV Crystalox, Uni Riga Sponsorship: BMBF Solar Valley Mitteldeutschland Silicon on glass T. Boeck, R. Heimburger, P. Schramm, T. Teubner Sponsorship: BP Solar, DFG