There is a continuous demand for more sensitive detectors of ultraviolet (UV) radiation. Popular silicon-based optoelectronic photodetectors perform poorly in UV spectrum. Integration of photoluminescent (PL) media capable of down-converting UV into visible (VIS) light (more suitable for silicon) with the photodetectors improve their UV sensitivity. We considered two such media: polymer nanocomposites impregnated with the nanoparticles (NPs) of perovskite CsPbBr3 and phosphor NaEuF4. We proposed to enhance the photoluminescence (PL) of the spectrum down-converting nanocomposites by embedding the nanoparticles (NPs) of high-entropy metal alloys (HEA) and using the surface plasmon polariton (SPP) resonance effect in such NPs. We proposed to fabricate HEA NPs and embed them in the nanocomposite using the patented concurrent multi-beam multi-target pulsed laser deposition (CMBMT-PLD) method. A two-step approach for making the nanocomposites impregnated with HEA NPs includes making HEA films using CMBMT-PLD followed by laser ablation of the films, formation of the HEA NPs during such ablation, and embedding them into a polymer matrix. By simulating the latter process with the ablation of the deposited HEA films in water the extension of the SPP resonance to the long-wave UV region (450 nm) has been demonstrated. A manifold improvement of the PL intensity of the nanocomposites due to SPP resonance in the embedded HEA NPs is expected. The obtained results will have an impact on the science and applications of short-wavelength sensors.
We report on polymer nanocomposite films with spectrum down-converting properties that can be transferred using pulsed laser deposition (PLD) on silicon avalanche photodiodes (APD) for responsive and fast UV sensing. The proposed spectrum down-convertors use two types of nanoparticles (NPs) embedded in a colorless polyimide matrix: semiconductor CdSe/ZnS core-shell quantum dots (QDs) and the QDs made of rare-earth (RE) doped lead halide perovskites CsPbX3 (X stands for Br and Cl). These NPs have efficient down-conversion of UV radiation into visible and near-infrared (NIR) light matching spectral responsivity of Si APD with the photoluminescence quantum yield (PLQY) from 50 to 190%. Once an APD detects visible/NIR signal, it responds with an electronic gain <106 and a response time of ~10 ns thus making rapid and strong UV sensing possible. Both types of NPs have strong absorption of UV and additionally protect the APD from degradation caused by UV radiation. CdSe/ZnS core-shell QDs convert UV spectrum in visible with a red peak at 631 nm using the down-shifting mechanism. The perovskite QDs doped with the ion of Yb3+ emitted in NIR with a peak at 980 nm due to the mechanism of down-conversion or quantum cutting. Both types of NPs were embedded in a polymer matrix and PLD deposited on a transparent substrate. We describe the results of characterization of the down-convertors using dynamic light scattering, X-ray diffraction, optical photoluminescence spectroscopy, and the photo-voltaic characteristics of silicon photodetectors integrated with the down-convertors.
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