Single-stage fabrication of buffer and window layers of CIGS thin-film solar cells using pulsed laser deposition

Abstract

Photovoltaic devices based on Cu(In,Ga)Se₂ (CIGS) are showing great promise as sources of clean and renewable energy production in the global efforts to reverse climate change. They hold several advantages over other technologies and are continuously being improved, leading to ever higher device efficiencies and lifetimes. However, state-of-the-art CIGS-based solar cells require a variety of techniques for the deposition of their constituent layers.

This work reports on the utilization of pulsed laser deposition (PLD) as a single technique for the preparation of the buffer (CdS) and window (intrinsic and Al-doped ZnO) layers of a complete CIGS-based solar cell. Employing a single deposition technique for the buffer and window layers greatly reduces manufacturing complexity. Furthermore, it potentially decreases processing time and fabrication costs through streamlined production lines. The methods and materials presented are also applicable to other solar cell types, such as Cu₂ZnSnS₄-based solar cells and other thin-film technologies.

The results presented herein discuss the methodology employed for the realization of the single-stage growth objective. The properties of the PLD-grown thin films with respect to structure, composition, and morphology were parametrically investigated through X-ray diffraction, energy-dispersive X-ray spectroscopy, scanning electron microscopy, and atomic force microscopy. These characterization results enabled the optimization of the PLD process parameters for each individual thin film, leading to improved device performance. Optoelectronic measurements were carried out in photovoltaic testing systems to assess the behavior of the complete solar cell. Using the optimal process parameters produced solar cells with PLD-grown buffer and window layers with 10.44% efficiency.