Thin film pc-Si by aluminium induced crystallization on metallic substrate

F Delachat,P Prathap,C Ducros,A Slaoui,F Antoni,C Cayron

doi:10.1051/epjpv/2013016

Abstract

Thin film polycrystalline silicon (pc-Si) on flexible metallic substrates is promising for low cost production of photovoltaic solar cells. One of the attractive methods to produce pc-Si solar cells consists in thickening a large-grained seed layer by epitaxy. In this work, the deposited seed layer is made by aluminium induced crystallization (AIC) of an amorphous silicon (a-Si) thin film on metallic substrates (Ni/Fe alloy) initially coated with a tantalum nitride (TaN) conductive diffusion barrier layer. Effect of the thermal budget on the AIC grown pc-Si seed layer was investigated in order to optimize the process (i.e. the quality of the pc-Si thin film). Structural and optical characterizations were carried out using optical microscopy, μ -Raman and Electron Backscatter Diffraction (EBSD). At optimal thermal annealing conditions, the continuous AIC grown pc-Si thin film showed an average grain size around 15 μ m. The grains were preferably (001) oriented which is favorable for its epitaxial thickening. This work proves the feasibility of the AIC method to grow large grains pc-Si seed layer on TaN coated metal substrates. These results are, in terms of grains size, the finest obtained by AIC on metallic substrates.

Highlights

Compared to classical photovoltaic technologies based on bulk crystalline silicon, thin film approach enables to reduce the material consumption drastically
Thin film polycrystalline silicon solar cells on non-silicon substrates are interesting to reduce the cost of photovoltaic electricity provided high quality silicon is produced and efficient optical confinement is applied
The aluminium induced crystallization (AIC) method is a relatively simple process, which enables a low thermal budget and a much shorter crystallization time compared to solid phase crystallization activated by classical annealing

Summary

Introduction

Compared to classical photovoltaic technologies based on bulk crystalline silicon, thin film approach enables to reduce the material consumption drastically. It allows large area deposition on low-budget foreign substrates. The thermal budget influence on the pc-Si film quality was studied for optimizing the AIC process on metallic substrate coated by TaN.

Experiment details

Results and discussions

Optical and structural analyses of the pc-Si layers

Optimization results

Conclusion