The Formation Mechanism of Cu(In0.7Ga0.3)Se2 Nanoparticles and the Densification Trajectory of the Se-Rich Quaternary Target by Hot Pressing

Qiang Ma,Zhaoyi Jiang,Yulong Zhang,Denghao Ma,Weijia Zhang,Chaoqun Lu,Zhiqiang Fan

doi:10.3390/cryst8030135

Abstract

In this paper, a method to obtain the CuInGaSe2 (CIGS) absorber layer with an appropriate selenium content is put forward, in which a Se-rich target is used to deposit a CIGS thin-film and this film is annealed in a Se-free inert atmosphere. The key issue of this method is the preparation of a Se-rich target with a homogeneous composition and a high-density. The formation mechanism of CuInSe2 and CuGaSe2 is investigated and the results point to the intermediate phase Cu2−xSe playing a role of a nucleation core. The sintering densification trajectory of the target with the addition of extra selenium is researched. Additionally, an effective way to avoid the sintering defects is proposed. Finally, a conversion efficiency of 11.2% for the CIGS solar cell is reached by sputtering from the obtained Se-rich target.

Highlights

Sputtering using quaternary CuInGaSe2 (CIGS) targets to deposit a thin-film of CIGS and annealing it in an atmosphere containing Se could prepare high-quality absorber layers and photovoltaic cells with high conversion efficiency [1,2]
The single-phase CIGS nanoparticles and Se-rich target are prepared in this study by the two-step hot-pressing method
The sintering curve indicates the sintering period of the Se-rich target could be divided into four stages, regardless of the addition of liquid selenium

Summary

Introduction

Sputtering using quaternary CuInGaSe2 (CIGS) targets to deposit a thin-film of CIGS and annealing it in an atmosphere containing Se could prepare high-quality absorber layers and photovoltaic cells with high conversion efficiency [1,2]. A novel method is proposed to obtain the deposited CIGS film with more selenium than that of the stoichiometric ratio by sputtering from a Se-rich target [8,9]. The deposited CIGS film can be annealed in an inert atmosphere in a selenium-free atmosphere at a high temperature. This way, the desirable selenium content of the absorber layer can be ensured. A novel and effective method is utilized to prepare the Se-rich target, by incorporating additional elemental selenium into the mixed film

Methods

Discussion

Conclusion