物理化学学报2021，Vol.37Issue(4)：160-166,7.DOI:10.3866/PKU.WHXB202007084
SCN掺杂提高CsPbl3胶体量子点的稳定性和光探测性能
SCN-doped CsPbl3 for Improving Stability and Photodetection Performance of Colloidal Quantum Dots
摘要
Abstract
Inorganic halide CsPbl3 perovskite colloidal quantum dots (QDs) possess remarkable potential in photovoltaics and light-emitting devices owing to their excellent optoelectronic performance.However,the poor stability of CsPbl3 limits its practical applications.The ionic radius of SCN-(217 pm) is comparable to that of I-(220 pm),whereas it is marginally larger than that of Br-(196 pm),which increases the Goldschmidt tolerance factor of CsPbl3 and improves its structural stability.Recent studies have shown that adding SCN-in the precursor solution can enhance the crystallinity and moisture resistance of perovskite film solar cells;however,the photoelectric properties of the material post SCN-doping remain unconfirmed.To date,it has not been clarified whether SCN-doping occurs solely on the perovskite surfaces,or if it advances within their structures.In this study,we synthesized inorganic perovskite CsPbl3 QDs via a hot-injection method.Pb(SCN)2 was added to the precursor for obtaining SCN--doped CsPbl3 (SCN-CsPbl3).X-ray diffraction (XRD),transmission electron microscopy (TEM),and X-ray photoelectron spectroscopy (XPS) were conducted to demonstrate the doping of SCN-ions within the perovskite structures.XRD and TEM indicated a lattice expansion within the perovskite,stemming from the large steric hindrance of the SCN-ions,along with an enhancement in the lattice stability due to the strong bonding forces between SCN-and Pb2+.Through XPS,we confirmed the existence of the S peak,and further affirmed that the bonding energy between Pb2+ and SCN-was stronger than that between Pb2+ and I-.The space charge limited current and time-resolved photoluminescence results demonstrated a decrease in the trap density of the perovskite after being doped with SCN-;therefore,the doping process mitigated the defects of QDs,thereby increasing their optical performance,and further enhanced the bonding energy of Pb-X and crystal quality of QDs,thereby improving the stability of perovskite structure.Therefore,the photoluminescence quantum yield (PLQY) of the SCN-CsPbl3 QDs exceeded 90％,which was significantly higher than that of pristine QDs (68％).The high PLQY indicates low trap density of QDs,which is attributed to a decrease in the defects.Furthermore,the SCN-CsPbl3 QDs exhibited remarkable water-resistance performance,while maintaining 85％ of their initial photoluminescence intensity under water for 4 h,whereas the undoped samples suffered complete fluorescence loss due to the phase transformations caused by water molecules.The SCN-CsPbl3 QDs photodetector measurements demonstrated a broad band range of 400-700 nm,along with a responsivity of 90 mA·W-1 and detectivity exceeding 1011 Jones,which were considerably higher than the corresponding values of the control device (responsivity:60 mA·W-1 and detectivity: 1010 Jones).Finally,extending the doping of SCN-into CsPbCI3 and CsPbBr3 QDs further enhanced their optical properties on a significant scale.关键词
无机卤化物钙钛矿/量子点/掺杂/稳定性/光电探测器Key words
Inorganic halide perovskite/Quantum dot/Doping/Stability/Photodetector分类
化学化工引用本文复制引用
郑超,刘阿强,毕成浩,田建军..SCN掺杂提高CsPbl3胶体量子点的稳定性和光探测性能[J].物理化学学报,2021,37(4):160-166,7.基金项目
The project was supported by the National Natural Science Foundation of China (51961135107,51774034),the Beijing Natural Science Foundation (2182039),the National Key Research and Development Program of China (2017YFE0119700).国家自然科学基金(51961135107,51774034),北京自然科学基金(2182039),国家重点研发计划(2017YFE0119700)资助项目 （51961135107,51774034）
