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Design of Solar Cells p⁺/n Emitter by Spin-On Technique

100%

El Amrani A., Boucheham A., Belkacem Y., Boufenik R., Boudaa M.

Acta Physica Polonica A

2017

vol. 132

issue 3

717-719

In this paper spin-on dopant diffusion has been investigated as a technique for fabrication of p⁺/n monocrystalline silicon solar cell emitters. A homogeneous spreading onto the front wafer surface has been achieved by using 2 ml of boron-dopant solution and three-step spin-profile. Study of the wafers stacking arrangement has revealed that the highest doping level and the best emitter sheet resistance uniformity were obtained using the back-to-back wafers arrangement. The N₂/O₂ gas ratio variation during the diffusion process has shown that a higher percentage of nitrogen yields a slightly lower emitter sheet resistance. Study on temperature dependence of as-processed emitter resistivity revealed that 910°C results in targeted sheet resistance of around 48 Ω/sq. Using these preliminary experimental results, a batch of 6 silicon wafers was processed. After BSG and BRL chemical removal, the batch average sheet resistance of the emitter was 49.50 Ω/sq. The uniformity of a wafer and of the batch was below 7% and 13%, respectively. The ECV and SIMS depth profiling have shown the electrically active and the total boron surface concentration of 1.5× 10²⁰ atoms/cm³ and 2.5× 10²⁰ atoms/cm³, respectively. The junction depth was around 0.3 μm. Finally, by increasing the oxygen flow rate we reached an average sheet resistance of 51 Ω/sq. and a junction depth of 0.35 μm.

Investigation of Degradation of Electrical Properties after Thermal Oxidation of p-Type Cz-Silicon Wafers

86%

Maoudj M., Bouhafs D., Bourouba N., Khelifati N., El Amrani A., Boufnik R., Hamida Ferhat A.

Acta Physica Polonica A

2017

vol. 132

issue 3

725-727

In this study we conducted thermal oxidation of Czochralski p-type <100> silicon wafers. The oxidation was carried out at temperatures in the range of 850-1000°C, in a gas mixture of N₂:O₂, in order to deposit a thin layer (10 nm) of thermal silicon dioxide (SiO₂), generally used in the surface passivation of solar cells. The measurements of effective minority carriers lifetime τ_{eff} using the quasi-steady-state photoconductance have shown degradation of different samples after oxidation process. The calculation of surface recombination velocity after the oxidation process at different temperatures, gave the same value of 40 cm s¯¹, showing a low surface recombination velocity and, therefore, a good surface passivation. Finally, a study based on sample illumination technique, allowed us to conclude that our samples are dominated by bulk Shockley-Read-Hall recombination, caused by Fe-related centers, thereby causing the degradation of the lifetime of minority carriers.

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2 Acta Physica Polonica A

2 2017

2 El Amrani A.

1 Belkacem Y.

1 Boucheham A.

1 Boudaa M.

1 Boufenik R.

1 Boufnik R.

1 Bouhafs D.

1 Bourouba N.

1 Hamida Ferhat A.

1 Khelifati N.

1 Maoudj M.

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Design of Solar Cells p⁺/n Emitter by Spin-On Technique

Investigation of Degradation of Electrical Properties after Thermal Oxidation of p-Type Cz-Silicon Wafers