基于空间电荷限制电流模型的FeCl3掺杂CBP的空穴迁移率研究

Investigation on hole mobility of FeCl_3-doped 4,4′-bis(carbazol-9-yl)-biphenyl by using space-charge-limited current model

基于不同浓度FeCl3掺杂的4,4′-N,N′-二咔唑基联苯(CBP)设计制作了一系列的单空穴有机电致发光器件(OLED),采用空间电荷限制电流法估算了具有不同浓度FeCl3掺杂的CBP的空穴迁移率,并与OLED中常用的空穴传输材料N,N′-二苯基-N,N′-(1-萘基)-1,1′-联苯-4,4′-二胺(NPB)进行了比较研究。结果表明,FeCl3掺杂CBP可以极大地提高CBP薄膜的空穴迁移率,当FeCl3的浓度为12%时空穴迁移率最大,在电场强度为0.5MV/cm的条件下迁移率为4.5×10-5cm2/V·s,即使在零电场条件下迁移率依然高达2.2×10-5 cm2/V·s,近似为常用空穴传输材料NPB空穴迁移率的4倍。用CBP∶12%FeCl3做空穴传输层,制备了OLED器件,最大亮度为68468cd/m2,相对于采用NPB做空穴传输层的参比器件提高了97%,最大电流效率为31.28cd/A,比参比器件提高了23%。器件亮度和效率的提高归因于空穴传输性能的改善,使得器件中载流子的传输更为平衡,从而提高了激子形成的几率,且减少了激子-极化子之间的淬灭。

A series of single hole devices are designed based on the different c oncentrations of FeCl3doped in 4,4′-Bis（9H-carbazol-9-yl）biphenyl （CBP）.The hole mob ilities of p-type doped CBP by FeCl3with various doping concentrations are estimated by using space-charge-limited current model,and compared with the mobility of NPB whi ch is a kind of hole transport material commonly used in organic electroluminescence devices .The results indicate that FeCl3doped CBP has significantly improved hole mobility .The highest hole mobility is achieved when the concentration of FeCl3is 12%.For an electr ic field of 0.5MV/cm,the estimated hole mobility of FeCl3-doped CBP with doping concentrat ion of 12% reaches 4.5×10^-5 cm2/V·s.Even in zero electric field,the hole mobilit y can reach 2.2×10^-5 cm2/V·s,which is nearly four times of that of NPB.High efficiency organic lig ht-emitting device is fabricated by using CBP：12% FeCl3as the hole transport layer.The device shows a maximum luminance of 68468cd/m2and a maximum current efficiency of 31.1cd/A,which are increased by 97% and 23% compared with those of the reference device,respectively.The improvements are a ttributed to the balanced charge carrier transport characteristic,which results in an increased charge ca rrier recombination probability and a decreased triplet-polaron （T-P） annihilation p robability.