Screening of suitable cationic dopants for solar absorber material CZTS/Se: A first principles study

M V Jyothirmai,Himanshu Saini,Ranjit Thapa,Noejung Park

doi:10.1038/s41598-019-52410-3

Abstract

The earth abundant and non-toxic solar absorber material kesterite Cu2ZnSn(S/Se)4 has been studied to achieve high power conversion efficiency beyond various limitations, such as secondary phases, antisite defects, band gap adjustment and microstructure. To alleviate these hurdles, we employed screening based approach to find suitable cationic dopant that can promote the current density and the theoretical maximum upper limit of the energy conversion efficiency (P(%)) of CZTS/Se solar devices. For this task, the hybrid functional (Heyd, Scuseria and Ernzerhof, HSE06) were used to study the electronic and optical properties of cation (Al, Sb, Ga, Ba) doped CZTS/Se. Our in-depth investigation reveals that the Sb atom is suitable dopant of CZTS/CZTSe and also it has comparable bulk modulus as of pure material. The optical absorption coefficient of Sb doped CZTS/Se is considerably larger than the pure materials because of easy formation of visible range exciton due to the presence of defect state below the Fermi level, which leads to an increase in the current density and P(%). Our results demonstrate that the lower formation energy, preferable energy gap and excellent optical absorption of the Sb doped CZTS/Se make it potential component for relatively high efficient solar cells.

Highlights

In the field of thin film based solar cells, the kesterite Cu2ZnSn(S/Se)[4] (CZTS/Se) has attracted substantial attention as a generation absorber materials owing to its favorable opto-electronic properties[1,2,3]
Our results demonstrate that the effect of dopants near the gap will tailor the electronic properties, which help to increase the optical absorption at visible region
We placed the dopants at all possible cationic sites and compared the relative formation energies (Ef). This is a commonly used method to correlate the corresponding degree of possibility of doping into the host lattice

Summary

Introduction

In the field of thin film based solar cells, the kesterite Cu2ZnSn(S/Se)[4] (CZTS/Se) has attracted substantial attention as a generation absorber materials owing to its favorable opto-electronic properties[1,2,3]. To study the intrinsic defect properties in CZTS/Se, we employed a well known correction method based on Lany and Zunger model[29] and calculated the defect formation energy as a function of Fermi energy (Ef) considering the values of chemical potential of point A (see the chemical potential region) as shown, where the slope of the line represents the charge state of a defect.

Results

Conclusion