基于電極修飾提高聚合物發(fā)光二極管性能的機理研究
發(fā)布時間：2018-09-10 18:45
【摘要】：有機電致發(fā)光器件(organic light-emitting devices,OLEDs)作為新一代顯示技術,與傳統(tǒng)的顯示技術相比,不但克服了視角窄、亮度低、工藝復雜等缺點,而且具有響應速度快、能耗低、全固態(tài)、厚度薄、自主發(fā)光、工作范圍寬且可使用柔性基板等優(yōu)越性。根據發(fā)光層材料的分子量的不同,OLEDs又可分為基于小分子材料的有機小分子電致發(fā)光器件(Small molecular OLEDs,Sm-OLEDs)和基于聚合物材料的聚合物電致發(fā)光器件(polymer light-emitting devices,PLEDs)。相比于小分子器件,PLEDs有著自身獨特的優(yōu)勢,如制備工藝簡單、成本低、利于大面積顯示發(fā)展等。盡管PLEDs近年來的發(fā)展日新月異,但器件的性能如效率、壽命、以及穩(wěn)定性等仍然有待提高。因此好的工藝手段和材料改進依然需要開發(fā)和研究。在工藝手段方面,對電極的修飾是非常有效的途徑,可通過改善載流子的注入,提高載流子的平衡,從而提高器件的發(fā)光亮度、發(fā)光效率、壽命和穩(wěn)定性等。電極修飾的方法眾多,其中溶劑處理有機層表面,優(yōu)化有機發(fā)光層/金屬電極層界面,是一種簡單、廉價并且高效的提高器件效率的方法,得到了人們的廣泛關注和研究�；诖�,本文主要通過電極修飾來提高PLED的器件性能。分別采用了極性溶劑處理法和優(yōu)化電極電阻率法,提高了PLED器件的載流子注入平衡,從而提高了器件效率,并探究了其背后的工作機理。具體研究內容分為以下兩個部分:一、以極性溶劑修飾發(fā)光層P-PPV的表面,來改善電子的注入,從而提高PLEDs器件的性能。相比于已報道的,以甲醇、乙醇或八氟戊醇等醇類極性溶劑為修飾溶劑的工作,我們采用非醇類、大偶極距的極性溶劑DMF來修飾綠色聚合物發(fā)光層P-PPV的表面。實驗數據顯示,對比無溶劑修飾的標準器件,甲醇修飾將器件的流明效率提高了17%,而DMF修飾將器件的流明效率提高了68%�？紤]到DMF的沸點較高,為了控制DMF在P-PPV表面的殘留量,我們將不同體積比的DMF摻雜在甲醇中,以DMF:甲醇的共混溶劑作為修飾溶劑來修飾P-PPV的表面。實驗結果顯示,相對于純甲醇修飾,共混溶劑修飾進一步大幅度的提高了器件的發(fā)光效率。隨著DMF在甲醇中的摻雜體積比從5%,10%,20%,40%提高到60%,相應的溶劑修飾后的器件的發(fā)光效率呈現拋物線形的變化規(guī)律,先增大再減小。摻雜比例為20%時,取得最高效率。修飾后PLEDs器件的發(fā)光效率相比于標準器件最多提高了126%,發(fā)光亮度最多提高了81%。可以見得,簡單的極性溶劑處理法卻能帶來器件性能顯著的提高。通過研究溶劑修飾對P-PPV發(fā)光層的表面形貌和粗糙度、紫外可見吸收、表面電勢和表面電子結構的影響,以及PLED器件的電子電流密度和開路電壓等的變化,深入而系統(tǒng)的研究了溶劑修飾提高PLEDs發(fā)光效率的原因。二、基于p型Si(p-Si)陽極的PLEDs。傳統(tǒng)的PLEDs采用銦錫氧化物(ITO)透明導電電極,其中的銦元素為在地殼中含量稀少,隨著ITO的廣泛使用,更加暴露了這一問題。而Si元素在地殼中的含量僅次于氧,占比26%。因此,以Si為陽極,不存在源材料短缺的問題。我們以p-Si為陽極,制備了高效率的PLEDs。我們研究了p-Si陽極的電阻率對PLED器件性能的影響。實驗結果顯示隨著p-Si電阻率的增加,相同電壓下,器件的電流密度單調增加,而發(fā)光亮度和效率先增后減。當p-Si電阻率為0.1Ω?cm-3,得到最佳功率效率。
[Abstract]:Organic light-emitting devices (OLEDs) as a new generation of display technology, compared with traditional display technology, not only overcome the shortcomings of narrow viewing angle, low brightness, complex technology, but also has the advantages of fast response, low energy consumption, all solid-state, thin thickness, self-luminescence, wide operating range and flexible substrate. According to the different molecular weight of the luminescent layer materials, OLEDs can be divided into organic small molecule OLEDs (Sm-OLEDs) and polymer light-emitting devices (PLEDs). Compared with small molecule devices, PLEDs have their own unique characteristics. Advantages, such as simple fabrication process, low cost, conducive to the development of large area display and so on. Despite the rapid development of PLEDs in recent years, the performance of devices such as efficiency, life, and stability still need to be improved. Therefore, good process means and material improvement still need to be developed and studied. There are many methods of electrode modification, among which solvent treatment of organic layer surface and optimization of the interface between organic light emitting layer and metal electrode layer are simple, cheap and efficient. Based on this, this paper mainly uses electrode modification to improve the performance of PLED devices. The polar solvent treatment method and the optimized electrode resistivity method are used respectively to improve the carrier injection balance of PLED devices, thereby improving the device efficiency and exploring the working mechanism behind them. The specific research contents are divided into the following two parts: 1. Polar solvents are used to modify the surface of phosphorescent layer P-PPV to improve the performance of PLEDs by improving the injection of electrons. DMF is used to modify the surface of green polymer light emitting layer P-PPV. The experimental results show that compared with the standard device without solvent modification, the luminous efficiency of the device is increased by 17% by methanol modification and 68% by DMF modification. The surface of P-PPV was modified by DMF doped in methanol with DMF:methanol as modifier. The experimental results showed that compared with pure methanol, the luminous efficiency of the device was further improved greatly. With the doping volume ratio of DMF in methanol increased from 5%, 10%, 20%, 40% to 60%, the corresponding solvent repair was carried out. The luminous efficiency of the modified PLEDs is increased by 126% and the luminous brightness is increased by 81% compared with the standard devices. It can be seen that simple polar solvent treatment can bring the device performance. The effect of solvent modification on the surface morphology and roughness, UV-Vis absorption, surface potential and surface electronic structure of P-PPV luminescent layer, as well as the changes of electronic current density and open-circuit voltage of PLED devices were studied. The reasons for the improvement of PLEDs luminescent efficiency by solvent modification were studied in detail and systematically. I(p-Si) anode PLEDs. Conventional PLEDs use indium tin oxide (ITO) transparent conductive electrodes, in which indium is scarce in the crust. With the widespread use of ITO, this problem is further exposed. The content of silicon in the crust is only second to that of oxygen, accounting for 26%. Therefore, there is no shortage of source materials for the Si anode. The effect of resistivity of p-Si anode on the performance of PLED devices was studied. The experimental results show that the current density increases monotonously with the increase of p-Si resistivity, while the luminous brightness and efficiency increase first and then decrease with the increase of p-Si resistivity. When p-Si resistivity is 0.1_?Cm-3, the optimal power efficiency is obtained.
【學位授予單位】：南京郵電大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TN383.1
本文編號：2235299
[Abstract]:Organic light-emitting devices (OLEDs) as a new generation of display technology, compared with traditional display technology, not only overcome the shortcomings of narrow viewing angle, low brightness, complex technology, but also has the advantages of fast response, low energy consumption, all solid-state, thin thickness, self-luminescence, wide operating range and flexible substrate. According to the different molecular weight of the luminescent layer materials, OLEDs can be divided into organic small molecule OLEDs (Sm-OLEDs) and polymer light-emitting devices (PLEDs). Compared with small molecule devices, PLEDs have their own unique characteristics. Advantages, such as simple fabrication process, low cost, conducive to the development of large area display and so on. Despite the rapid development of PLEDs in recent years, the performance of devices such as efficiency, life, and stability still need to be improved. Therefore, good process means and material improvement still need to be developed and studied. There are many methods of electrode modification, among which solvent treatment of organic layer surface and optimization of the interface between organic light emitting layer and metal electrode layer are simple, cheap and efficient. Based on this, this paper mainly uses electrode modification to improve the performance of PLED devices. The polar solvent treatment method and the optimized electrode resistivity method are used respectively to improve the carrier injection balance of PLED devices, thereby improving the device efficiency and exploring the working mechanism behind them. The specific research contents are divided into the following two parts: 1. Polar solvents are used to modify the surface of phosphorescent layer P-PPV to improve the performance of PLEDs by improving the injection of electrons. DMF is used to modify the surface of green polymer light emitting layer P-PPV. The experimental results show that compared with the standard device without solvent modification, the luminous efficiency of the device is increased by 17% by methanol modification and 68% by DMF modification. The surface of P-PPV was modified by DMF doped in methanol with DMF:methanol as modifier. The experimental results showed that compared with pure methanol, the luminous efficiency of the device was further improved greatly. With the doping volume ratio of DMF in methanol increased from 5%, 10%, 20%, 40% to 60%, the corresponding solvent repair was carried out. The luminous efficiency of the modified PLEDs is increased by 126% and the luminous brightness is increased by 81% compared with the standard devices. It can be seen that simple polar solvent treatment can bring the device performance. The effect of solvent modification on the surface morphology and roughness, UV-Vis absorption, surface potential and surface electronic structure of P-PPV luminescent layer, as well as the changes of electronic current density and open-circuit voltage of PLED devices were studied. The reasons for the improvement of PLEDs luminescent efficiency by solvent modification were studied in detail and systematically. I(p-Si) anode PLEDs. Conventional PLEDs use indium tin oxide (ITO) transparent conductive electrodes, in which indium is scarce in the crust. With the widespread use of ITO, this problem is further exposed. The content of silicon in the crust is only second to that of oxygen, accounting for 26%. Therefore, there is no shortage of source materials for the Si anode. The effect of resistivity of p-Si anode on the performance of PLED devices was studied. The experimental results show that the current density increases monotonously with the increase of p-Si resistivity, while the luminous brightness and efficiency increase first and then decrease with the increase of p-Si resistivity. When p-Si resistivity is 0.1_?Cm-3, the optimal power efficiency is obtained.
【學位授予單位】：南京郵電大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TN383.1
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