CuInSe_(2)量子点的制备及光电应用研究进展

Progresses in CuInSe_(2) Quantum Dots:Synthesis and Optoelectronic Applications

与Cd系量子点相比,CuInSe_(2)量子点具有低毒性、较高的光吸收系数和较宽的光谱吸收范围等优势,在太阳能电池、光电催化、光电探测器等光电器件领域展现出巨大的应用潜力。尽管大量文献报道了CuInSe_(2)量子点的控制合成和光电器件研究,其性能仍有较大的提升空间。总结了CuInSe_(2)量子点的控制合成方法,包括一锅法、热注入法和阳离子交换法,概述了各种合成方法的优势与不足。并重点介绍了CuInSe_(2)量子点在敏化太阳能电池、光电催化、探测器方面的应用研究进展及提高性能的方法,如对量子点进行合金化处理、配体交换以及构建核壳结构等。最后,针对CuInSe_(2)量子点在光电器件应用中的性能提升提出优化方法,如合成方法及后处理工艺优化、器件结构构筑优化及电荷传输材料改性等,并对其应用前景进行了展望。

Colloidal semiconductor quantum dots(QDs)have attracted great attention from optoelectronic community in recent years due to their unique physical properties,such as the quantum confinement effect,high extinction coefficients and multiple exciton generation.Among various QDs,Cd-based chalcogenide QDs,including CdS and CdSe,were most frequently investigated due to their superior performance.However,the limited light absorption in the visible range and the toxicity of cadmium restricted their wide application.CuInSe_(2)QDs showed low toxicity,high light absorption coefficient and wide light absorption range,which could reach the near-infrared region(NIR).Therefore,CuInSe_(2)QDs demonstrated greatpotential for solar cells,photoelectron chemical water splitting and photodetectors.Although a great number of efforts were devoted to the controllable synthesis and photoelectronic application of CuInSe_(2)QDs,the under standing of the photophysical properties and their relationship with the device performance was still very poor.In this review,we firstly presented the advances in the synthesis methods of CuInSe_(2)QDs such as one-pot synthesis,hot-injection method and cation exchange method and discussed advantages and disadvantages of each approach.For example,hot-injection method was the most commonly used synthesis method,the rapid reaction and high nucleation rate allowed for relatively uniform size distribution and high-quality products.Through modulating reaction parameters,monodispersed and narrow size distributed CuInSe_(2)quantum dots were achieved.However,this method couldn’t be used for large-scale production of high-quality QDs due to its drawbacks on precise control of nucleation temperature and injection practicality.The one-pot synthesis was another method to prepare QDs by mixing all the precursors,ligands and solvents to the reaction vessel,and then directly heating to a specific temperature.This method enabled the scalable synthesis,while it was usually accompanied with the production of by-products.Due to the large difference in the reaction activities of In and Cu precursors,it was difficult to accurately control the morphology of QDs by hot-injection method or one-pot synthesis.In addition,cation exchange method was a post-synthesis process that involved replacing the cation in the guest nanocrystal with the target cation.CuInSe_(2)quantum dots,nanorods,nanoplates were achieved through this method.Although the cation exchange method permitted the synthesis of anticipated morphologies,it might introduce surfacetraps,which reduced the photoelectric performance in turn.Subsequently,the photoelectronic applications of CuInSe_(2)QDs in quantum dot sensitized solar cells(QDSCs),photoelectrochemical(PEC)water splitting and photodetectors were discussed.The light absorption spectrum of CuInSe_(2)QDs ranges from UV-visible to the NIR region(~1200 nm),which was in good match with the solar spectrum.The theoretical power conversion efficiency of CuInSe_(2)QDs based QDSCs was higher than that of Cd-based QDs,thus CuInSe_(2)QDs were considered as one of the most promising photosensitizers for QDSCs.Great efforts were paid to improve the performance of CISe QDSCs through alloying,construction of core/shell structure,surface passivation,and placement of long-chain ligands with short-chain ligands to eliminate defects,which enhanced the light absorption or improved the charge transfer.These contributed to ever-increasing power conversion efficiency.Up to now,the power conversion efficiency of CISe QDSCs reached 15.2%,which was the highest certified value for QDSCs.Different to QDSCs which could convert solar energy into electricity,photoelectrochemical(PEC)water splitting was an effective approach of converting solar energy into H_(2).CISe QDs was one of the most promising sensitizers to enhance light harvesting to the visible/NIR range.Similar to QDSCs,QDs based PEC cells also required efficient charge carrier transfer and high light harvesting.Thus,similar strategies with QDSCs were applied to improve the performance.However,the stability of both CuInSe_(2)QDSCs and PEC cells was stillvery poor.Photodetectors could transformthe optical signal into electrical signals.CISeQDs-based photodetectors could achieve a response into NIR range,however,their performance still lagged behind that of PbSQDs-based NIR photodetectors or the silicon photodetectors due to the poor surface properties or the low crystallinity of CuInSe_(2)QDs.Besides surface decoration or improving the crystallinity of CuInSe_(2)QDs,coupling with other semiconductors was also an effective strategy to improve the detection performance.Finally,challenges and opportunities of CuInSe_(2)QDs were proposed and discussed.Although the performance of CuInSe_(2)QDs based photoelectric devices were greatly improved in recent years,they still couldn’t reach the commercial application standard.The device performance could be improved by controlling the synthesis process and post-treatment process to regulate properties of quantum dots,device architecture optimization or modification of the charge carrier transfer layer.In addition,the stability issue should be paid more attention.The Cu+in CuInSe_(2)QDs was easy to migrate,and the effect of Cu+migration on the crystal structure and photoelectric performance were still unclear.Therefore,studies on Cu+migration should be strengthened.Besides the photoelectric applications,the exploration of other promising application areas such as biological probe deserved much attention.