No abstract

Yb3+/Er3+ codoped La2S3 upconversion (UC) phosphors have been synthesized using high‐temperature solid‐state method. Under 971‐nm excitation, the maximum luminescence power can reach 0.64 mW at the excitation power density of 16 W/cm2 and an absolute power yield of 0.36% was determined by an absolute method at the excitation power density of 3 W/cm2, and the quantum yield of La2S3:Yb3+, Er3+ (green ~0.18%, red ~0.03%, integration ~0.21) was comparable to that of NaYF4:Yb3+, Er3+ nanocrystals (integration ~0.005–0.30). Frequency upconverted emissions from two thermally coupled excited states of Er3+ were recorded in the temperature range 100–900 K. The maximum sensitivity of temperature sensing is 0.0075 K−1. As the excitation power density increases, the temperature of host materials rapidly rises and the top temperature can reach to 600 K. Given the intense UC emission, high sensitivity, as well as good photothermal stability, La2S3:Yb3+/Er3+ phosphor can become a promising composite material for photothermal ablation of cancer cells possessing the functions of temperature sensing and in vivo imaging.

In phototransistors, the photovoltaic‐induced current is proportional to the turn‐on voltage shift and the total number of trapped charges. However, it is challenging to obtain a high turn‐on voltage shift simply by using minority carrier trap sites because high‐concentration carrier trap sites introduce strong current traps and carrier recombination. In this study, spatially separated, hole/electron, dual traps are introduced into a phototransistor, demonstrating the possibility of combining hole and electron traps without and with illumination, respectively, to obtain a large turn‐on voltage shift. The near‐infrared phototransistor demonstrates a high light‐to‐dark current ratio (1 × 106) alongside a turn‐on voltage shift of 28 V. The current quenching of the charge trap is effectively compensated by the threshold voltage shift, resulting in an increase of the drain–source current. The dual traps induce a low‐noise current and a high photoresponsivity (5.26 × 103 A W–1) under the same gate voltage (Vg = 0 V), exhibiting an ultrahigh detectivity (D1/f∗ = 1.88 × 1015 Jones; Dshot∗= 8.21 × 1016 Jones).

We report a novel OPT working mode by photoelectric dual control. After each light switch, the dark current is erased by the gate voltage in depletion mode which remains unchanged during light off; the photocurrent increases by the device converting to accumulation mode when the light is on.