Lu Li,Weiyi Chen,Meng Wang,Xinjiang Shi,Shiming Zhang,Debao Xiao
In this paper, we present the first application of organic hole-transporting semiconductors 4,4′,4′'-tris(carbazol-9-yl)triphenylamine (TCTA) and 4,4′-cyclohexylbis[N,N-bis(4-methylphenyl) aniline] (TAPC) in electrochromism area, demonstrating that TCTA or TAPC is suitable for use as hole-transporting materials on the anode of 1,1′-bis(3-sulfopropyl) viologen (SPV)-based electrochromic devices. For such devices, we obtain a decreased driving voltage of SPV-based electrochromic devices down to −2.0 V in the presence of TCTA or TAPC with comparison to that of ca. −2.5 V in the absence of the hole-transporting material. The optical contrast of the device increased from 57.19 % (without hole-transport layer) to 66.41 % (TCTA) or 62.97 % (TAPC) at 533 nm. The response time of 66.2 s in the absence of hole-transporting layer can decrease to 30.6 s with TCTA and 62.7 s with TAPC, respectively. The coloration efficiency of the as-fabricated devices at 533 nm can reach from 67.3 cm 2 /C (SPV-only) up to 153.2 cm 2 /C (TCTA) and 80.5 cm 2 /C (TAPC). This work paved a new way for boosting electrochromic performances of viologen-based devices via electrode modification of anode by hole-transporting material TCTA and TAPC which have been used effectively and efficiently in organic electroluminescent devices and solar cells.
Quantum dot light-emitting diodes (QLEDs) have received extensive academic and industrial attention for the exceptional properties of QDs including size-tunable emission wavelengths , narrow emission linewidths and inherent photo-physical stability. It is vital for the QLEDs performance to select appropriate hole transport materials due to the imbalance carrier injection caused by the higher electron mobility in most devices. In this paper, a small molecular material 1,1-bis [4-[N,N′-di (p-tolyl)amino]phenyl]-cyclohexane (TAPC) with high hole mobility was used to physically blend with poly-N-vinylcarbazole (PVK) as the hole transport layer (HTL) by solution processing. In the inverted red QLEDs, when the optimized mass ratio of the mixture HTL (2:1 of PVK:TAPC) was adopted, the device turn-on voltage drops from 4.0 V to 2.4 V, the maximum current efficiency (CE max ) reaches 19.3 cd/A, which is 50% higher than that of the standard devices (with only PVK as HTL), the maximum power efficiency (PE max ) significantly increases from 5.2 lm/W to 16.7 lm/W, increased by more than 3 times, the external quantum efficiency (EQE) reaches 45% enhancement from 8.7% to 12.6%, and the optimized device lifetime is enhanced by 4.5 times. The improvement of performances can be mainly attributed to the addition of TAPC with high hole mobility and suitable energy levels, and the unique charge generation between PVK:TAPC and hole injection layer (HIL) interface. The results demonstrate that the blending of the small-molecule and polymer hole transport materials will be a feasible approach to improve the performance in the QLEDs.
Liyan Yang,Feilong Cai,Yu Yan,Jinghai Li,Dan Liu,Andrew J. Pearson,Tao Wang
The π-conjugated organic small molecule 4,4′-cyclohexylidenebis[ N , N -bis(4-methylphenyl) benzenamine] (TAPC) has been explored as an efficient hole transport material to replace poly(3,4-ethylenedio-xythiophene):poly(styrenesulfonate) (PEDOT:PSS) in the preparation of p-i-n type CH 3 NH 3 PbI 3 perovskite solar cells. Smooth, uniform, and hydrophobic TAPC hole transport layers can be facilely deposited through solution casting without the need for any dopants. The power conversion efficiency of perovskite solar cells shows very weak TAPC layer thickness dependence across the range from 5 to 90 nm. Thermal annealing enables improved hole conductivity and efficient charge transport through an increase in TAPC crystallinity. The perovskite photoactive layer cast onto thermally annealed TAPC displays large grains and low residual PbI 2 , leading to a high charge recombination resistance. After optimization, a stabilized power conversion efficiency of 18.80% is achieved with marginal hysteresis, much higher than the value of 12.90% achieved using PEDOT:PSS. The TAPC-based devices also demonstrate superior stability compared with the PEDOT:PSS-based devices when stored in ambient circumstances, with a relatively high humidity ranging from 50 to 85%.
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