Sub-Picosecond Micromachining of Monocrystalline Silicon for Solar Cell Manufacturing

Katarzyna Garasz,Marek Kocik

doi:10.3390/app10207277

Katarzyna Garasz, Marek Kocik

Open Access

https://doi.org/10.3390/app10207277

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Abstract

In this study a prototype sub-picosecond laser was investigated for cutting and scribing of silicon wafers. The Yb:KYW laser used for this investigation, unlike ultrashort systems used previously, generates pulses of 650 fs, i.e., between the pico and femtosecond range. The laser was placed in a micromachining setup, involving a galvo scanner and a telecentric lens. A study of the influence of the processing parameters on the crater width, depth, and quality of machining was carried out. The optimal parameters were found to be 343 nm, 200 kHz, 7 mm/s, and 15 pattern repetitions. The experiments were performed using samples of a silicon wafer of 210-µm thickness. The experimental results show that the sub-picosecond laser can be a promising and competitive tool for solar cell micromachining. In comparison to the commercially available ultrashort pulse laser systems, we find the sub-picosecond laser to be a more cost efficient and reliable source, than a femtosecond one. In addition, the prototype Yb:KYW design offers some unique parameters, such as repetition rate in the range of 100–400 kHz, UV wavelength or obtainable laser fluence close to the silicon ablation thresholds.

Highlights

The rapid growth of the photovoltaics market requires advances in PV manufacturing and technologies that would translate into further cost reductions, as well as quality and efficiency increase of the solar cells [1]
Laser technology has already been widely applied in photovoltaic production for the last two decades, in many different ways (Figure 1) [2,3]
There are processes directly related to silicon wafers micromachining

Summary

Introduction

The rapid growth of the photovoltaics market requires advances in PV (photovoltaics) manufacturing and technologies that would translate into further cost reductions, as well as quality and efficiency increase of the solar cells [1]. They include dicing, nano and micro-structuration of the surface, and antireflection coating or nanoparticle absorbing [4,5,6,7,8,9,10,11]. According to Mazur et al, a simple irradiation of the silicon surface with ultrashort laser pulses may improve the cell efficiency [4,5,6,7,8]. One of the common micromachining processes engaged in increasing the efficiency of the solar cells is the so-called junction isolation (laser edge isolation)

Methods

Results

Conclusion