Recently, the research group of Professor Song Hongwei (correspondent) from the State Key Laboratory of Integrated Optoelectronics, School of Electronic Science and Engineering, Jilin University reported that three elements (Cr3+, Yb3+ and Ce3+) doped CsPbCl3 perovskite quantum dots (PeQDs) were synthesized by high-temperature thermal injection method, and coated on the surface of Si, achieving high performance response in ultraviolet band and visible near infrared band. The related paper titled "Ultra-efficient quantum cutting Cr3+, Ce3+, Yb3+ triple doped perovskite quantum dots with external quantum efficiency over 70% for ultraviolet response of Gao Zengqiang silicon photodetector" was published in Nano Energy.
Paper link:
/science/article/pii/s 22 1 1285520308557
The results show that when the Cr3+ doping concentration is 8.2%, the quantum yield of CsPbCl3 increases from 8% to 82%, and it shows good stability. After standing for 250 days, the PL intensity after doping remained basically unchanged. However, the PL intensity of undoped PeQDs decreased by 52% after five days. This characteristic mainly comes from: (1) doping greatly reduces the defect state density; (2) Through DFT calculation, the main defect Cl vacancy before doping disappears after doping.
Figure 1. Crystal structure; (b) TEM images before and after doping; (c) the change of crystal plane spacing and (d) the change of d)XRD diffraction peak before and after doping; (e) XPS image after doping.
Figure 2. (a) absorption image, (b)PL image and (c) variation of quantum yield with different Cr3+ doping amount; (d) Long-term PL intensity comparison between undoped and Cr3+-8.2% doped; (e) Comparison of defect density and fluorescence lifetime with different Cr3+ doping amounts; (f) Calculation results of defect levels before and after doping.
The absorption spectrum in Figure 3(a) shows that the absorption in ultraviolet band, especially in deep ultraviolet band, is greatly enhanced after adding rare earth ion Ce3+. This is mainly due to the 5d high energy state of Ce3+ ion. The quantum yield is improved because the emission level of Ce3+ provides a band gap matching channel between PeQDs and Yb3+ ions, which greatly improves the quantum tailored quantum yield of Yb3+ ions, reaching 175%. Three-ion-doped CsPbCl3: Cr3+, Yb3+ and Ce3+ quantum dots were prepared on the surface of Si, and were prepared at 200? The external quantum efficiency of more than 70% in the range of 400 nm is equivalent to that in visible and near infrared bands. (Quantum clipping refers to the physical phenomenon that every time a fluorescent material absorbs a high-energy photon, it will release two low-energy photons, and its theoretical quantum yield is 200%. )
Figure 3. Optical characterization and energy band interpretation of single element, double element and triple element doping.
Figure 4. (a) Schematic diagram of SiPDs and quantum trimmed PeQDs integrated devices under full-spectrum illumination. (b) photocurrent of Si PDs coated with SiPDS, CsPbCl3: Cr3+, Yb3+peqd and SiPDS coated with CsPbCl3: Cr3+, Yb3+peqd under illumination of 240 nm, 360 nm and 980 nm. (c, d) Responsiveness and external quantum efficiency of the three devices. (e) Time-resolved photocurrent of photodiode under 360 nm illumination. (f) The photocurrent of silicon quantum dots coated with CSP BCL3: Cr3+, Yb3+ and Ce3+ quantum dots changes with time.
Generally speaking, a new strategy is proposed to improve the quantum yield of quantum dots and improve the poor response of silicon quantum dots in ultraviolet band. It provides an idea for synthesizing other quantum dots or nanocrystalline materials with high quantum yield. At the same time, the absorption enhancement strategy of rare earth ion Ce3+ doping in ultraviolet band is also expected to improve the performance of other ultraviolet photodetectors. (Text: Unplanned)