High performance DUV to NIR broadband silicon photodetectors enabled by Zn2+, Tb3+-codoped Cs2NaGdCl6 double perovskites nanocrystal integration

Abstract

Silicon photodetectors (Si PDs) have garnered significant attention for photoelectric applications. However, their performance in the deep-ultraviolet to ultraviolet (DUV-UV) range remains limited, due to high reflection coefficients and shallow penetration depths. In this work, we employed the extremely efficient UV to visible emissions Zn²⁺, Tb³⁺-codoped Cs₂NaGdCl₆ double perovskite nanocrystals (DPNCs) to boost the DUV-UV response of Si PDs. The pristine Cs₂NaGdCl₆ DPNCs exhibit characteristic blue emission from self-trapped excitons (STEs), while Tb³⁺ doping enables green emission by efficient energy transfer from STEs to Tb³⁺. Meanwhile, because Zn²⁺ ion has a smaller ionic radius and the closed character of its 3d-shell, the Zn²⁺ doping can decrease defect and improve optical performance of Cs₂NaGdCl₆ DPNCs, leading to the enhanced 4f-4f transitions of Tb³⁺. Finally, by spin coating the Zn²⁺, Tb³⁺-codoped Cs₂NaGdCl₆ DPNCs in the front of the Si PDs, we achieve remarkable DUV-UV responsivity enhancement, including high responsivity of 93.6 mA/W and outstanding external quantum efficiency of 35.46% at UV illumination. This work shows a paradigm for developing environmentally stable, full-spectrum PDs through rational design of lead-free rare-earth-based DPNCs/silicon heterojunctions.