The Synthesis Of Nonblinking Gradient-alloyed Quantum Dots And Their Application In Light-emitting Diodes

Colloidal quantum dots?QDs?have been enthusiastically investigated with regard to the potential applications in lasers,biosensors,thin-film transistors,solar cell and light-emitting diodes,owing to the unique optical properties,including high photoluminescence?PL?quantum yield?QY?,saturated pure color,easily tunable size-dependent emission wavelength,high stability.With the improvement of device structure and the targeted development of QD emitters,quantum dot light emitting diodes?QLED?are considered to be the most promising next generation products for display and solid state lighting compared to OLED.However,there are still some limitations in the application of QLED.Because QDs would have a blinking phenomenon arising from the Auger effect emerges,bringing further negative effect on the efficiency under the operational condition.Therefore,how to obtain the non-blinking quantum dots is the key to improve the device efficiency.In the past,methods for solving such problems mainly focused on the study of core-shell quantum dots,but it is not conducive to precisely control the synthesis of QDs and reduce the preparation cost,as a result of the complicated growth process of core/shell QDs.Therefore,it is more desirable to use a simple approach to obtain the“perfect QD”,which displays the high PL QY,high stability,single-channel PL decay dynamics,and non-blinking behaviour.Among them,the method of synthesizing quantum dots with alloy structure is considered to be effective,mainly because the alloy structure can regulate the energy band structure and the luminescent properties without changing the particle size and dispersion.Nevertheless,there is less research on the synthesis of quantum dots with high quantum yield and good stability in non-blinking alloy structures by a simple one-pot method.On the basis of the above problems,the work in this paper is given as follows.?1?By adjusting the ratio of Se and S,the high quality of non-blinking,single-exponential photoluminescence?PL?decay dynamics green CdSe_1-xS_x were prepared by noninjection method.When the ratio of Se and S is 1:8,the synthesized QDs with PL located at 511 nm show PL FWHM?Full Width at Maximum?of 28 nm and high PL quantum yields about 90%,and the quantum dots has a single-exponential photoluminescence decay dynamics?"light state"time>98%?features.By applying the“ideal”CdSe_1-xS_x QDs into QLED with conventional device structure,the best device displays the maximum values of 92,330 cd m^-2,50.3 cd A^-1 and 14.5%for luminance,current efficiency and EQE,respectively.Such excellent performance is attributed to the combined effects of several factors,including high PL QY,single-exponential PL decay and non-blinking behaviour of QDs.?2?The high quality of non-blinking,single-exponential PL decay dynamics green CdSe_x S_1-x were prepared by one-pot method.By tuning the composition and others conditions,the results show that the optical parameters of PL intensity and quantum yields are improved obviously.Comparing various properties of QLED,The performance of QLED devices has been improved to a certain extent.These devices exhibit maximum luminance of 236,281 cd/m² and the maximum EQE of 17.4%,and CE?current efficency?up to 70.46 cd A^-1,respectively.The improvement is attributed to the fact that the high-quality of QDs.The the gradient alloy QDs which we synthesized here has unique optical properties,that is,non-blinking behavior,which ensures that the QDs continue to emit light efficiently under continuous carrier injection.