Investigation of Low-Cost Surface Processing Techniques for Large-Size Multicrystalline Silicon Solar Cells

Yuang-Tung Cheng,Yung-An Lu,Jia-Jhe Liou,Song-Yeu Tsai,Kang L Wang,Shun-Hsyung Chang,Jyh-Jier Ho,William J Lee

doi:10.1155/2010/268035

Abstract

The subject of the present work is to develop a simple and effective method of enhancing conversion efficiency in large-size solar cells using multicrystalline silicon (mc-Si) wafer. In this work, industrial-type mc-Si solar cells with area of125×125 mm2were acid etched to produce simultaneouslyPOCl3emitters and silicon nitride deposition by plasma-enhanced chemical vapor deposited (PECVD). The study of surface morphology and reflectivity of different mc-Si etched surfaces has also been discussed in this research. Using our optimal acid etching solution ratio, we are able to fabricate mc-Si solar cells of 16.34% conversion efficiency with double layers silicon nitride (Si3N4) coating. From our experiment, we find that depositing double layers silicon nitride coating on mc-Si solar cells can get the optimal performance parameters. Open circuit (Voc) is 616 mV, short circuit current (Jsc) is 34.1 mA/cm2, and minority carrier diffusion length is 474.16 μm. The isotropic texturing and silicon nitride layers coating approach contribute to lowering cost and achieving high efficiency in mass production.

Highlights

The multicrystalline silicon solar cell is still heavily dependent on the material base in the semiconductor industry, and features an excellent stability, mature technology, and easy acquisition [1, 2]
We have shown that the major advantages of the process are texture of a large size multicrystalline silicon (mc-Si) with suitable acid solution ratio, no grainboundary delineation, and significant reproducibility
The n-type emitter was formed in the solar cell process by phosphorus diffusion at temperatures of 835◦C for 10 minutes predeposition followed by 20 minutes drive-in

Summary

Introduction

The multicrystalline silicon (mc-Si) solar cell is still heavily dependent on the material base in the semiconductor industry, and features an excellent stability, mature technology, and easy acquisition [1, 2]. In order to commercialize high-efficiency solar cell for optional consumer electronics, it is essential to produce cells with low cost on Czochralski (CZ) mc-Si wafers and simple fabrication processes proposed in our research. The essential factors of achieving high efficiencies of Sibased wafer are the large minority carrier recombination lifetime and long diffusion length in mc-Si solar cells [16, 17]. We use large size CZ mc-Si wafer in order to investigate the influence of the grain boundary on the minority charge carrier diffusion length. While the result of the bare wafers indicates a good effectiveness in acid etching experiment, a silicon nitride (Si3N4) coated on the surface of a real cell by plasma-enhanced chemical vapor deposited (PECVD) further changes the overall reflection properties. Our experiment mainly focuses on the concept of utilizing the DL refractive index of Si3N4 to minimize the reflection losses and passivation of the solar-cell surface

Experiments

Treatment Result and Discussion

Findings

Conclusion