Tuning to the band gap by complex defects engineering: insights from hybrid functional calculations in CuInS2

• Published in: Journal of physics. D, Applied physics Vol. 51; no. 2
• Main Authors: Yang, Pei, Shi, Li-Jie, Zhang, Jian-Min, Liu, Gui-Bin, Yang, Shengyuan A, Guo, Wei, Yao, Yugui
• Format: Journal Article
• Language: English
• Published: IOP Publishing 17.01.2018
• Subjects: band gap tuning; complex defect; Cu/In molar ratio; CuInS; first principles; formation energy
• ISSN: 0022-3727; 1361-6463
• DOI: 10.1088/1361-6463/aa9c17

Tuning band gaps of semiconductors in terms of defect control is essential for the optical and electronic properties of photon emission or photon harvesting devices. By using first-principles calculations, we study the stability condition of bulk CuInS2 and formation energies of point and complex defects in CuInS2 with hybrid exchange-correlation functionals. We find that at Cu-rich and In-poor conditions, 2Cui  +  CuIn is the main complex defect, while InCu  +  2VCu is the main complex defect at In-rich and Cu-poor conditions. Such stable complex defects provide the feasibility of tuning band gaps by varying the [Cu]/[In] molar ratios. These results present how the off-stoichiometry CuInS2 crystal structures, and electronic and optical properties can be optimized by tuning the [Cu]/[In] ratio and Fermi level, and highlight the importance of complex defects in achieving better photoelectric performance in CuInS2. Such band gap tuning in terms of complex defect engineering is a general approach and thus applicable to other photo-harvest or light-emission semiconductors.