混合鹵素CsPbBrxI3–x鈣鈦礦量子點具有良好光譜可調性，在純紅光鈣鈦礦發光二極管領域中具有良好的應用潛力。然后，該類量子點面臨著表面缺陷和不穩定性這兩大難題，嚴重阻礙了其在高性能器件中的實際應用價值。
基于此，鄭州大學張繼斌研究員與華中科技大學屠國力教授等人報道了采用釔陽離子(Y3+)摻雜和苯基膦酸(PPA)鈍化的協同策略來解決這些問題。其中，引入Y3+離子摻雜后，量子點的形成能得以降低，而碘化物空位缺陷的形成能則有所增加。PPA則通過其膦氧化物基團與未配位的 Pb2+離子配位，成功實現了對表面缺陷的有效鈍化。并且，PPA的羥基還能與相鄰鹵素離子形成氫鍵，抑制了鹵素離子的遷移，進一步增強了鈍化效果。
最終，Y/PPA 共改性量子點表現出了卓越的穩定性，光致發光量子產率近乎達到100%。基于這些量子點的鈣鈦礦發光二極管具有出色的光譜穩定性，外量子效率達到24.5%，是基于 CsPbBrxI3–x量子點的純紅光鈣鈦礦發光二極管效率最高者之一。
該工作得到了國家重點研發計劃、國家自然科學基金、中國博士后科學基金等項目資助。
Figure 1. (a) Electrostatic potential (ESP) map of PPA molecules. (b) Schematic illustration of CsPbBrxI3-xNCs before and after synergistic modification of Y3+ ion doping and PPA passivation. TEM images of (c) pristine, (d) Y-doped, and (e) Y/PPA NCs. The insets show corresponding HRTEM images. (f) Elemental mapping images of Y/PPA NCs.
Figure 2. (a) XRD patterns, (b) PL and Absorption spectra, (c) Time-resolved PL decay curves of pristine, Y-doped, and Y/PPA NCs. TA spectra of (d) pristine, (e) Y-doped, and (f) Y/PPA NCs at different probe delay times.
Figure 3. (a) FTIR spectra of pristine NCs, Y/PPA NCs, and neat PPA. (b) 1H and (c) 31P NMR spectra of neat PPA, a mixture of PPA and PbBr2, and a mixture of PPA and PbI2 in dimethyl sulfoxide (DMSO-d6) solution. High-resolution XPS spectra of (d) Y 3dand (e) P 2p of Y/PPA NCs before etching and after etching. (f) High-resolution XPS spectra of Pb 4f of pristine, Y-doped, and Y/PPA NCs.
Figure 4. PL spectra of (a) pristine, (b) Y-doped, and (c) Y/PPA NC films at different times (photostability test: under UV light continuous irradiation). (d) PL spectra of pristine NC films on day 0 and day 5 (stability test: 40 ℃ and 80% RH). The insets show the corresponding photographs of pristine NC films under daylight (left) and UV light (right) on day 0 and day 5. (e) PL spectra of Y-doped NC films on day 0 and day 16 (stability test: 40 ℃ and 80% RH). The insets show the corresponding photographs of Y-doped NC films under daylight (left) and UV light (right) on day 0 and day 16. (f) PL spectra of Y/PPA NC films on day 0 and day 29 (stability test: 40 ℃ and 80% RH). The insets show the corresponding photographs of Y/PPA NC films under daylight (left) and UV light (right) on day 0 and day 29.
Figure 5. (a) Device structure of PeLEDs. (b) Current density−voltage−luminance curves of PeLEDs. (c) EQE−current density curves of PeLEDs. EL spectra of PeLEDs based on (d) pristine, (e) Y-doped, and (f) Y/PPA NCs at different bias voltages. The inset shows a working PeLED.
