Due to their excellent carrier mobility,high absorption coefficient and narrow bandgap,most 2D IVA metal chalcogenide semiconductors(GIVMCs,metal=Ge,Sn,Pb;chalcogen=S,Se)are regarded as promising candidates for realiz...Due to their excellent carrier mobility,high absorption coefficient and narrow bandgap,most 2D IVA metal chalcogenide semiconductors(GIVMCs,metal=Ge,Sn,Pb;chalcogen=S,Se)are regarded as promising candidates for realizing high-performance photodetectors.We synthesized high-quality two-dimensional(2D)tin sulfide(SnS)nanosheets using the physical vapor deposition(PVD)method and fabricated a 2D SnS visible-light photodetector.The photodetector exhibits a high photoresponsivity of 161 A·W-1 and possesses an external quantum efficiency of 4.45×10^(4)%,as well as a detectivity of 1.15×10^(9) Jones under 450 nm blue light illumination.Moreover,under poor illumination at optical densities down to 2 mW·cm^(-2),the responsivity of the device is higher than that at stronger optical densities.We suggest that a photogating effect in the 2D SnS photodetector is mainly responsible for its low-light responsivity.Defects and impurities in 2D SnS can trap carriers and form localized electric fields,which can delay the recombination process of electron-hole pairs,prolong carrier lifetimes,and thus improve the low-light responsivity.This work provides design strategies for detecting low levels of light using photodetectors made of 2D materials.展开更多
Lanthanide doped NaYF4 microcrystals were synthesized via a facile hydrothermal method. Multicolor upconversion luminescence was observed in NaYF4 microcrystals doped with yb^3＋/Er^3＋, yb^3＋/Tm^3＋, and yb^3＋/Er^3...Lanthanide doped NaYF4 microcrystals were synthesized via a facile hydrothermal method. Multicolor upconversion luminescence was observed in NaYF4 microcrystals doped with yb^3＋/Er^3＋, yb^3＋/Tm^3＋, and yb^3＋/Er^3＋/Zm^3＋ under the excitation of 980 nm infrared light. Importantly, the excitation power density dependence of upconversion emission intensity indicated clearly the energy transfer from Tm^3＋ to Er^3＋ ions under the excitation of low power density （5× 10^2× 10^2 W/cm^2）. Meanwhile, the inverse energy transfer from Er^3＋ to Tm^3＋ ions under the excitation of relatively higher power density （4.1 × 10^4.9× 10^4 W/cm^2） was also revealed. This was a direct evidence for reversible energy transfer between Er^3＋ and Tm^3＋ ions. Under the excitation of high power density （4.1 ×10^4-4.9× 10^4 W/cm^2）, dark sensitizers were also motivated so that the bottleneck effect of high concentration Yb^3＋ ion doping was broken. This was the main reason for realizing high upconversion efficiency of the samples with heavy doping of Yb^3＋ ion.展开更多
基金the National Natural Science Foundation of China(Grant Nos.1872251 and 11875229).
文摘Due to their excellent carrier mobility,high absorption coefficient and narrow bandgap,most 2D IVA metal chalcogenide semiconductors(GIVMCs,metal=Ge,Sn,Pb;chalcogen=S,Se)are regarded as promising candidates for realizing high-performance photodetectors.We synthesized high-quality two-dimensional(2D)tin sulfide(SnS)nanosheets using the physical vapor deposition(PVD)method and fabricated a 2D SnS visible-light photodetector.The photodetector exhibits a high photoresponsivity of 161 A·W-1 and possesses an external quantum efficiency of 4.45×10^(4)%,as well as a detectivity of 1.15×10^(9) Jones under 450 nm blue light illumination.Moreover,under poor illumination at optical densities down to 2 mW·cm^(-2),the responsivity of the device is higher than that at stronger optical densities.We suggest that a photogating effect in the 2D SnS photodetector is mainly responsible for its low-light responsivity.Defects and impurities in 2D SnS can trap carriers and form localized electric fields,which can delay the recombination process of electron-hole pairs,prolong carrier lifetimes,and thus improve the low-light responsivity.This work provides design strategies for detecting low levels of light using photodetectors made of 2D materials.
基金Project supported by the National Natural Science Foundation of China(21301058,61274026)Innovation Foundation of Hunan University of Science and Technology(S140036)
文摘Lanthanide doped NaYF4 microcrystals were synthesized via a facile hydrothermal method. Multicolor upconversion luminescence was observed in NaYF4 microcrystals doped with yb^3＋/Er^3＋, yb^3＋/Tm^3＋, and yb^3＋/Er^3＋/Zm^3＋ under the excitation of 980 nm infrared light. Importantly, the excitation power density dependence of upconversion emission intensity indicated clearly the energy transfer from Tm^3＋ to Er^3＋ ions under the excitation of low power density （5× 10^2× 10^2 W/cm^2）. Meanwhile, the inverse energy transfer from Er^3＋ to Tm^3＋ ions under the excitation of relatively higher power density （4.1 × 10^4.9× 10^4 W/cm^2） was also revealed. This was a direct evidence for reversible energy transfer between Er^3＋ and Tm^3＋ ions. Under the excitation of high power density （4.1 ×10^4-4.9× 10^4 W/cm^2）, dark sensitizers were also motivated so that the bottleneck effect of high concentration Yb^3＋ ion doping was broken. This was the main reason for realizing high upconversion efficiency of the samples with heavy doping of Yb^3＋ ion.
