物理化学学报 >> 2019, Vol. 35 >> Issue (8): 896-902.doi: 10.3866/PKU.WHXB201810064

论文 上一篇    

C60与MoO3混合材料做空穴注入层的单层有机电致发光器件

薛楷,闫敏楠,潘飞,田梦颖,潘旭东,张宏梅*()   

  • 收稿日期:2018-10-30 录用日期:2018-12-11 发布日期:2018-12-14
  • 通讯作者: 张宏梅 E-mail:iamhmzhang@njupt.edu.cn
  • 基金资助:
    国家自然科学基金(61674081);国家自然科学基金(51333007)

Single-Layer Organic Light-Emitting Devices with C60 and MoO3 Mixed Materials as Hole Injection Layer

Kai XUE,Minnan YAN,Fei PAN,Mengying TIAN,Xudong PAN,Hongmei ZHANG*()   

  • Received:2018-10-30 Accepted:2018-12-11 Published:2018-12-14
  • Contact: Hongmei ZHANG E-mail:iamhmzhang@njupt.edu.cn
  • Supported by:
    the National Natural Science Foundation of China(61674081);the National Natural Science Foundation of China(51333007)

摘要:

我们制备研究了基于结构为氧化铟锡(ITO)/C60 (1.2 nm):MoO3 (0.4 nm)/1, 3, 5-三(1-苯基-1H-苯并咪唑-2-基)苯(TPBi):三(2-苯基吡啶)铱[Ir(ppy)3] (33%,90 nm)/LiF (0.7 nm)/Al (120 nm)的高效绿色磷光单层有机发光二极管(OLED)。分别将C60,MoO3与C60:MoO3混合物作为空穴注入层(HIL)作为对比。TPBi在发光层中起着主体以及电子传输材料的双重作用。在使用电子传输型主体的单层OLED中,空穴注入层性质对于调节电子/空穴注入以获得电荷载流子传输平衡起重要作用。因此,适当调节空穴注入层是实现高效单层OLED的关键因素。由于MoO3较大的电子亲和能(6.37 eV)会诱导电子从C60的最高占据分子轨道(HOMO)能级转移至MoO3,从而形成C60阳离子,并使得Mo元素的价态从+6降至+5,C60:MoO3混合就可以较好的调节空穴注入性质。最终实现最大电流效率为35.88 cd∙A−1的单层有机发光器件。

关键词: 单层, 有机发光二极管, 空穴注入层, 混合材料, 电荷载流子平衡

Abstract:

Multilayer phosphorescent organic lighting-emitting diodes (PHOLEDs) with complicated device configurations have greatly increased the complexity of manufacturing and the fabrication cost. Therefore, there is strong incentive to develop simplified OLEDs, such as a single-layer device that has the structure of anode/hole injection layer (HIL)/emissive layer/electron injection layer/cathode. However, because of the absence of a carrier transport layer, the single-layer device suffers from severe charge injection difficulties and unbalanced carrier transport. Hence, the performances of single-layer devices reported so far have not been satisfactory. It has been proved that the modification of the electrode/organic interface could influence carrier injection to improve the device performance in multilayer PHOLEDs. Modification of the electrode/organic interface is more essential for achieving high-performance single-layer OLEDs. In this work, efficient green phosphorescent single-layer OLEDs based on the structure of indium tin oxide (ITO)/C60 (1.2 nm):MoO3 (0.4 nm)/1, 3, 5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi):fac-tris(2-phenylpyridine)iridium [Ir(ppy)3]/LiF (0.7 nm)/Al (120 nm) were fabricated. C60, MoO3, and C60:MoO3 were applied as the HILs, respectively, for comparison. The layer of TPBi played a dual role of host and electron-transporting material within the emission layer. Thus, the properties of the HILs play an important role in the adjustment of electron/hole injection to attain transport balance of the charge carriers in single-layer OLEDs with electron-transporting hosts. It is found that appropriate adjustment of the HIL is a key factor to achieve high-efficiency single-layer OLEDs. The large affinity of MoO3 (6.37 eV), inducing electron transfer from the highest occupied molecular orbital of C60 to MoO3, results in the formation of C60 cations and induces the decrease of the valence from Mo+6 to Mo+5; therefore, C60:MoO3 can adjust the hole injection properties well. Finally, a single-layer OLED with a maximum current efficiency of 35.88 cd∙A−1 was achieved. Compared with devices with MoO3 (28.99 cd∙A−1) or C60 (10.46 cd∙A−1) as HILs, the device performance was improved by 24% and 243%, respectively. Overall, a novel and effective method of using different mixed ratios of C60 and MoO3 as the HIL to realize effective charge carrier regulation is proposed, and it is of great significance for fabricating high-performance single-layer OLEDs.

Key words: Single-layer, Organic light-emitting diodes, Hole injection layer, Mixed materials, Balance of charge carriers