Jens Moschner

Optimization and characterization of remote plasma-enhanced chemical vapor deposition silicon nitride for the passivation of p-type crystalline silicon surfaces

In a recent letter [Lauinger et al., Appl. Phys. Lett. 68, 1232 (1996)] we have shown that record low effective surface recombination velocities Seff of 4 cm/s have been obtained at ISFH on low-resistivity (1 Ω cm) p-type crystalline silicon using microwave-excited remote plasma-enhanced chemical vapor deposition (RPECVD) of silicon nitride at low temperature (300–400 °C). As an important application, this technique allows a simple fabrication of rear-passivated high-efficiency silicon solar cells with monofacial or bifacial sensitivity. In this work, we present details of the required optimization of the PECVD parameters and a characterization of the resulting silicon nitride films. All deposition parameters are shown to strongly affect Seff as well as the stability of the films against the ultraviolet (UV) photons of terrestrial sunlight. A clear correlation between Seff and the film stoichiometry is observed, allowing a simple control and even a rough optimization of the surface passivation quality by ...

Rear-Surface Passivation Technology for Crystalline Silicon Solar Cells: A Versatile Process for Mass Production

Over the past few years, significant progress has been made in integrating cell structure improvements on the cell front side into mass production, such as, e.g., selective emitters. With these improvements, the large-area aluminum back-surface field clearly limits the efficiency of typical industrial cells. Dielectric passivation of the cell rear side provides a means for significant improvement. However, it needs to be adapted to different wafer materials and cell structures in order to obtain economic efficiency, allowing for its implementation in mass production. In this paper, we report on our cost-effective passivated emitter and rear cell (PERC) technology that easily adapts to various wafer materials, such as multicrystalline, quasi-monocrystalline, and Czochralski-grown monocrystalline material. It is suitable for wafer thicknesses down to 120 µm and all base resistivities in the range from 1 to 3.5 Ω·cm. Additionally, we investigate the compatibility with homogeneous and selective emitters on the cell front side. For commercially available Czochralski wafers, we present an efficiency gain of more than 1.0% absolute in cell efficiency with a peak cell efficiency of up to 20.2%. The usability of our PERC solar cells in modules is demonstrated with a 289-W module containing 60 PERC cells. To emphasize the efficacy of high-performance cells in modules, a simple cell-to-module factor calculation is presented.

Thermo-catalytic deposition of silicon nitride - a new method for excellent silicon surface passivation

The deposition of silicon nitride (SiN) films for the surface passivation of crystalline silicon solar cells by thermo-catalytic chemical vapor deposition (cat-CVD), also known as hot-wire CVD, was investigated. A detailed study was performed to assess the useful parameter range. We found that with this new technique very high gas yield and deposition rate can be reached using a very simple deposition source. Excellent surface passivation of p-type silicon could be achieved for the first time using SiN films deposited by cat-CVD. A very strong correlation of the film composition and surface recombination with the gas flow ratio was observed. The films have been applied to the front and back of solar cells to demonstrate their effectiveness. A detailed comparison between cat-CVD and high-quality plasma-deposited films has been performed, in which the films prove very similar.

UV stability of highest-quality plasma silicon nitride passivation of silicon solar cells

The UV stability of Si solar cells passivated by low-temperature remote PECVD silicon nitride films is tested. Perfect stability of the front surface passivation and the rear surface passivation of both p-n junction as well as MIS-IL Si solar cells is observed. Using the microwave-detected photoconductance decay (MW-PCD) method, a very small and slow degradation of the differential effective surface recombination velocity S/sub eff.d/ is observed at silicon nitride-passivated p-Si surfaces corresponding to the nonmetallized rear surface regions of bifacial cells. However, the degradation is too small to have any impact on the long-term stability of encapsulated 17-18% rear efficient bifacial cells. Thin-silicon-oxide/silicon-nitride double layers incorporating Cs as used at the front surface of MIS-IL solar cells provide perfectly stable and excellently low differential S/sub eff.d/ values of 23 cm/s on 1.5-/spl Omega/cm wafers. Applied to the rear surface of bifacial Si solar cells, this double-layer scheme gives the potential of stable rear efficiencies of even 20%.