• Chinese Optics Letters
  • Vol. 23, Issue 1, (2025)
Huang Song, Wu Anmin, Song Guanting, Cao Jiaxin, Yao Jianghong, Wu Qiang, Gao Weiqing, Xu Jingjun
Author Affiliations
  • Hefei University of Technology
  • Nankai University
  • show less


    Black silicon materials prepared via micro-structuring and hyperdoping by ultrafast laser irradiation have attracted immense attention owing to their high absorption and photon sensitivity across a broadband spectral range. However, a conflict exists between the repair requirements for the high amount of laser-induced damages and the thermally unstable hyperdoped impurities, resulting in low photon sensitivity and rapid decay at sub-bandgap wavelengths for the annealed black silicon. In this work, the properties of titanium (Ti) hyperdoped silicon have been explored using first-principle calculations. The findings of the study revealed that the interstitial Ti atoms exhibit a deep impurity band and low formation energy in silicon, which may be responsible for the stable sub-bandgap absorption that was achieved. Furthermore, femtosecond laser irradiation and rapid thermal annealing have been applied to manufacture Ti-hyperdoped black silicon (b-Si:Ti). The b-Si:Ti compound prepared by hyperdoping displayed high absorption across the visible and infrared ranges, with absorptance exceeding 90% for visible light and 60% for sub-bandgap wavelengths. Additionally, the sub-bandgap absorption remained high even after intense thermal annealing, indicating a stable deep-level impurity of Ti in silicon. The experimental findings were consistent with the simulation results and complemented each other to reveal the physical mechanisms responsible for the high performance of b-Si:Ti. The results thus demonstrate promising prospects for the application of black silicon in high-efficiency solar cells, photoelectric imaging, and flip-chip interconnection systems.
    Manuscript Accepted: Jun. 4, 2024
    Posted: Jul. 10, 2024