Automated Array Assembly, Phase 2

The solar cell module process development activities in the areas of surface preparation are presented. The process step development was carried out on texture etching including the evolution of a conceptual process model for the texturing process; plasma etching; and diffusion studies that focused on doped polymer diffusion sources. Cell processing was carried out to test process steps and a simplified diode solar cell process was developed. Cell processing was also run to fabricate square cells to populate sample minimodules. Module fabrication featured the demonstration of a porcelainized steel glass structure that should exceed the 20 year life goal of the low cost silicon array program. High efficiency cell development was carried out in the development of the tandem junction cell and a modification of the TJC called the front surface field cell. Cell efficiencies in excess of 16 percent at AM1 have been attained with only modest fill factors. The transistor-like model was proposed that fits the cell performance and provides a guideline for future improvements in cell performance

Comparison Of Front - And Back - Junctions Monocrystalline Silicon Solar Cell

This thesis undertakes fabrication, characterization and optimization of front and back junction solar cells. As part of our effort on cost reduction strategy, a simple technologies of conventional furnace processing (CFP) and rapid thermal processing (RTP) has been compared. Tesis ini menjalankan fabrikasi, pencirian dan pengoptimuman sel-sel suria persimpangan depan dan belakang. Sebagai sebahagian usaha kami iaitu strategi pengurangan kos, satu teknologi mudah pemprosesan relau konvensional (CFP) dan pemprosesan terma yang pesat (RTP) telah dibandingka

Fabrication and characterisation of Si micropillar PV structures

Arrays of vertical silicon micropillar radial junction solar cells have been fabricated by diffusion of direct application spin on dopant and from the vapour phase through proximity rapid thermal diffusion. The micropillars were fabricated by optical lithography and deep reactive ion etching. The micropillar arrays show superior antireflective properties over the measured spectrum and good correlation to finite difference time domain modelling of identical geometry arrays. Junctions formed by a conventional spin on doping process of phosphorus containing dopant solution produced Suns-Voc values in the region of 0·3 V. This value is likely due to difficulties encountered in achieving an even distribution of dopant over the entire surface of the arrays. An alternative method utilising spin on dopant but employing an intermediate vapour phase diffusion step produced promising results with Suns-Voc values reaching 0·5 V following a post-diffusion drive-in ste

Fabrication and characterisation of Si micropillar PV structures

Arrays of vertical silicon micropillar radial junction solar cells have been fabricated by diffusion of direct application spin on dopant and from the vapour phase through proximity rapid thermal diffusion. The micropillars were fabricated by optical lithography and deep reactive ion etching. The micropillar arrays show superior antireflective properties over the measured spectrum and good correlation to finite difference time domain modelling of identical geometry arrays. Junctions formed by a conventional spin on doping process of phosphorus containing dopant solution produced Suns-Voc values in the region of 0·3 V. This value is likely due to difficulties encountered in achieving an even distribution of dopant over the entire surface of the arrays. An alternative method utilising spin on dopant but employing an intermediate vapour phase diffusion step produced promising results with Suns-Voc values reaching 0·5 V following a post-diffusion drive-in ste

Fabrication and characterisation of Si micropillar PV structures

Arrays of vertical silicon micropillar radial junction solar cells have been fabricated by diffusion of direct application spin on dopant and from the vapour phase through proximity rapid thermal diffusion. The micropillars were fabricated by optical lithography and deep reactive ion etching. The micropillar arrays show superior antireflective properties over the measured spectrum and good correlation to finite difference time domain modelling of identical geometry arrays. Junctions formed by a conventional spin on doping process of phosphorus containing dopant solution produced Suns-Voc values in the region of 0.3 V. This value is likely due to difficulties encountered in achieving an even distribution of dopant over the entire surface of the arrays. An alternative method utilising spin on dopant but employing an intermediate vapour phase diffusion step produced promising results with Suns-Voc values reaching 0.5 V following a post-diffusion drive-in step

Poly-Si passivating contacts formed via spin-on doping for c-Si solar cells

With the constant improvement of crystalline silicon solar cells over the last decades, the carrier recombination and transportation at the contacts have become limiting factors to efficiency improvement for crystalline silicon solar cells. A potential solution is to use passivating contact, which suppresses carrier recombination while simultaneously ensures efficient majority carrier transportation. The polycrystalline silicon (poly-Si) passivating contact has shown a low carrier recombination current density, a low contact resistivity and a high thermal stability which can be easily integrated with the current high efficiency industrial silicon solar cell production lines. A wide range of doping methods have been employed to fabricate poly-Si passivating contacts, but only a small amount of work has been presented on spin-on doping process. The spin-on doping technique involves less dangerous dopant precursors than other doping techniques like dopant gas diffusion and a simpler process tool than e.g. ion implantation, and it may promote the doping process versatility based on its features of diverse dopant elements, wide dopant concentration range, and the ability of single-side doping. However, more comprehensive and detailed investigations are required for the poly-Si passivating contacts fabrication by using spin-on doping. Thus, in this thesis we focus on the application of spin-on doping process on industrially processed poly-Si passivating contacts. We performed detailed investigations on phosphorus and boron spin-on dopants. For both phosphorus and boron spin-on doping, the various spin speed and acceleration during spin coating process show slight impacts on passivation quality. Besides, a longer baking time leads to better passivation and lower sheet resistance. In addition, the drive-in process yields large impacts on passivation and electrical properties. Implied open-circuit voltages of ~730 or 705 mV are obtained after 975 or 950 centigrade drive-in process and a forming gas annealing (FGA), for phosphorus or boron case respectively. A low contact resistivity below 5 mOhmcm2 for both, phosphorus or boron, spin-on doping cases were achieved. These results are to our knowledge the highest iVOC values achieved by spin-on doping to date and are close to the performance of gas diffused or ion implanted poly-Si contacts. This shows the potential of spin-on doping process as alternative to traditional gas diffusion or ion implantation doping methods

Direct writing for silicon wafer solar cells

Ph.DDOCTOR OF PHILOSOPH