Extraction and analysis of TCO coated glass from waste amorphous silicon thin film solar module

Abstract

Considering the fast pace of the development of the Photovoltaic (PV) market and the installations in last two decades and also the increasing scarcity of resources for semiconductor materials, recycling waste PV modules including thin film is very important. Transparent conducting oxides (TCOs) are extensively used as front contact electrodes in thin-film photovoltaic devices. The paper presents, the new strategies developed to extract TCO coated glass from thin film amorphous silicon PV end-of-life modules. The recycling of thin film PV modules is based on a very simple approach that includes chemical, thermal and mechanical treatments. Optimised solutions of 1 M NaOH and 1 M KOH were used to extract TCO coated glass. The feasibility of the processing steps was demonstrated on laboratory scale size module and the etching rate for P, I, and N-layers of amorphous silicon is also studied. The extracted TCO was identified as fluorine-doped tin oxide (FTO) using X-ray diffraction and UV–visible spectroscopy techniques. The laser scribed FTO glass was successfully extracted without damaging the properties of the material. The extracted FTO has very low resistivity and sheet resistance in the range of 10−4 Ω-cm and 11.74 Ω/sq. respectively, has uniform transmission throughout the measured film surface of 2 cm2 in the visible region having bandgap ∼3.8eV. The recycling cost and current market value of the recycled FTO are also estimated for all the installed capacities of amorphous silicon. Considering the TCO properties, extracted FTO has the potential for its reuse in the fabrication of new thin film PV modules and other optoelectronic device applications as well.