Tris(carbazol-9-yl)-triphenylamine Research Articles

Theoretical insights into long-range coupling of electron-hole pairs in TCTA–PO-T2T exciplex

This work reports theoretical investigations concerning long-range coupling of electron-hole pairs in spatially separated exciplex (SSE) systems via Density Functional Theory and Time-Dependent Density Functional Theory. Based on TCTA−PO-T2T parent exciplex, where 4,4′,4″-Tris(carbazol-9-yl)triphenylamine (TCTA) serves as donor (D) and 2,4,6-Tris[3-(diphenylphosphinyl)phenyl]-1,3,5-triazine (PO-T2T) as acceptor (A), SSEs are constructed by intentionally tuning the D−A distance. The calculation results demonstrate that all SSEs, even if the D−A distance is over 14 Å, exhibit the clear and strong charge transfer character in terms of DCT, qCT, and t indexes. As the D−A distance increases, the energy gap of SSEs is increased, resulting in the blueshift of emission spectra. Calculation and experiment results show a good consistency, indicating that our model could well describe SSEs. Meanwhile, the reduced energy gap between CT and 3LE and more degenerate states could boost reverse intersystem crossing via vibronic coupling and hyperfine coupling, eventually improving the electroluminescent performance of SSEs. Our study suggests that manipulation of relative energy alignment via controlling D−A distance not only promotes the properties of exciplexes, but also offers guidance for designing thermally activated delayed fluorescence emitters through-space charge transfer.

Hole-transporting materials boost optoelectronic performance: Their first application in electrochromic device based on 1,1′-Bis(3-sulfopropyl) viologen

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 cm2/C (SPV-only) up to 153.2 cm2/C (TCTA) and 80.5 cm2/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.

Synergistic nucleation regulation using 4,4',4''-tris(carbazol-9-yl)-triphenylamine and moisture for stably air-processed high-performance perovskite photodetectors.

Perovskite photodetectors (PPDs) offer a promising solution with low cost and high responsivity, addressing the limitations of traditional inorganic photodetectors. However, there is still room for improvement in terms of the dark current and stability of air-processed PPDs. In this study, 4,4',4''-tris(carbazol-9-yl)-triphenylamine (TCTA) was utilized as a nucleation agent to enhance the quality of perovskite films. The synergistic effect of TCTA and moisture promotes rapid nucleation of PbI2-PbCl2, resulting in an increased nucleation rate and the elimination of pinholes in the film. By employing additive engineering, we obtained a PbI2-PbCl2 layer with high coverage, leading to a low density of traps in the corresponding perovskite film. Consequently, the modified PPD exhibits a remarkable reduction in dark current density by over one order of magnitude, reaching 2.4 × 10-10 A cm-2 at -10 mV, along with a large linear dynamic range (LDR) of 183 dB. Furthermore, the resulting PPD demonstrates remarkable stability, retaining 90% of the initial external quantum efficiency (EQE) value even after continuous operation for over 3200 hours. Owing to a fast response time in the nanosecond range, the PPD could convert modulated light signals into electrical signals at a speed of 588 Kbit s-1, highlighting the great potential in the field of optical communication.

Enhanced efficiency of the Sb2Se3 thin-film solar cell by the anode passivation using an organic small molecular of TCTA

Antimony selenide (Sb2Se3) is an emerging solar cell material. Here, we demonstrate that an organic small molecule of 4, 4', 4''-tris(carbazol-9-yl)-triphenylamine (TCTA) can efficiently passivate the anode interface of the Sb2Se3 solar cell. We fabricated the device by the vacuum thermal evaporation, and took ITO/TCTA (3.0 nm)/Sb2Se3 (50 nm)/C60 (5.0 nm)/Alq3 (3.0 nm)/Al as the device architecture, where Alq3 is the tris(8-hydroxyquinolinato) aluminum. By introducing a TCTA layer, the open-circuit voltage is raised from 0.36 to 0.42 V, and the power conversion efficiency is significantly improved from 3.2% to 4.3%. The TCTA layer not only inhibits the chemical reaction between the ITO and Sb2Se3 during the annealing process but it also blocks the electron diffusion from Sb2Se3 to ITO anode. The enhanced performance is mainly attributed to the suppression of the charge recombination at the anode interface.

Investigating the donor:acceptor ratio in thermally activated delayed fluorescence light-emitting macromolecules

We report the synthesis of solution-processable branched thermally activated delayed fluorescence (TADF) macromolecules with a 2,4,6-triphenyl-1,3,5-triazine acceptor (A) core and one, two, or three 3,6-diphenylamine carbazole donors (D). 2-Ethylhexyl surface groups were used as the solubilising groups. Increasing the number of donors was found to red shift the emission from green to orange. The materials were all found to have TADF character with the triply substituted compound (D3A) having a ΔΕST of 0.01 eV. The charge transfer emission from the materials was found to be broad and featureless at both room and low (77 K) temperature for both the prompt (nanosecond) and delayed (microsecond) emission, with no structured phosphorescence that could be assigned to a locally excited triplet state observed at low temperature. The solution PLQY of the emitter with one donor (DA) was found to be the highest at 55% with the macromolecules with two (D2A) or three (D3A) donors being similar at around 40%. The photophysical properties were found to be strongly dependent on the medium in which they were measured. Interestingly, in the host used for the organic light-emitting diodes (OLEDs), the PLQYs were all similar at around 65%. The charge mobility of neat films of the materials was found to be dependent on the number of donor units with D2A having relatively balanced hole and electron mobilities of order 10−6 cm2/Vs. Simple solution processed two-layer OLEDs composed of 5 mol% of the compounds in 4,4′,4"-tris(carbazol-9-yl)triphenylamine (TCTA) were all found to have maximum external quantum efficiencies of near 10% and in the case of D3A a maximum luminance of over 8700 cd/m2.

Light-emitting dendrimer:exciplex host-based solution-processed white organic light-emitting diodes

Solution-processed monochrome and white organic light-emitting diodes (OLEDs) that have a light-emitting layer composed of a 4,4′,4″-tris(carbazol-9-yl)triphenylamine (TCTA) and (5-terphenyl-1,3-phenylene)bis(diphenylphosphine oxide) (POPH) exciplex host and soluble blue, green and/or red phosphorescent dendrimers have been fabricated and characterised. The OLED performance characteristics were found to be scan dependent, with the first scans having large external quantum efficiencies (EQEs) at low luminance, with subsequent scans showing stable performance. The monochrome (blue, green and red) films were found to have high photoluminescence quantum yields, relatively balanced hole and electron mobilities, and the OLEDs had stable EQEs of between 9 and 12% at 100 cd m −2 over multiple scans. The blue, green and red emissive materials were blended with the exciplex host, with their ratio tuned to achieve white emission. The optimal blend ratio provided white OLEDs that had EQEs of 11.7% and 10.6% at 100 cd m −2 and 1000 cd m −2 , respectively. The best balance of 1931 Commission Internationale d'Eclairage (CIE) coordinates (0.40,0.40), Colour Rendering Index (70), and Delta uv (0.003) was achieved for an OLED with the light-emitting layer containing the blue, green and red dendrimers in a ratio of 20.0:0.4:0.8 wt%. A feature of the white OLEDs was the stability of the CIE coordinates, with a change of only (0.013,0.005) between a luminance of 100 cd m −2 and 4000 cd m −2 . • A common exciplex host composed for solution processed blue, green, red and white emissive OLEDs. • Monochrome light-emitting dendrimer:exciplex host blend films have relatively balanced hole and electron mobilities. • Monochrome OLEDs with external quantum efficiencies of up to 22.5%. • White emitting OLEDs external quantum efficiencies of 10.6% at 1000 cd m −2 • White OLEDs with stable CIE coordinates across a broad range of luminance.

Harnessing bipolar acceptors for highly efficient exciplex-forming systems

Two bipolar molecules CzT2.1 and CzT2.2 are examined as electron acceptors to form exciplexes with electron donors 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC) and 4,4′,4′′-tris(carbazol-9-yl)-triphenylamine (TCTA), respectively.

Efficiency and color-temperature-stability improvements in exciplex-based phosphorescent organic light-emitting diodes with a quantum well structure

Currently, exciplex has drawn a great deal of attention due to its potential for efficient electroluminescence and for use as a host. In this study, we used 4,4′,4"-Tris(carbazol-9-yl) triphenylamine (TCTA) and 1,3,5-Tri(m-pyridin-3-ylphenyl) benze nee (TmPyPB) to form an exciplex host, where Bis[2-(4,6-difluorophenyl)pyridinato-C2,N](picolinato)iridium(III)(FIrpic) was used as the dopant to emit blue phosphorescent light. Additional FIrpic and Bis(1phenylisoquinoline) (acetylacetonate) iridium(III) emission layers were inserted in the proposed structure to investigate how the recombination area of carriers shifts with the increase of voltage. TCTA and non-doped FIrpic layers were then inserted in both sides of the emission layer to confine the carriers, and the thickness of the emission layer was also optimized to improve the current efficiency of the proposed devices. The efficiency of the devices was increased from 56 cd/A to 63.6 cd/A with the additional quantum well structure and an emission layer thickness of 15 nm. The current efficiency reported in this paper was fairly high as compared with other published data on blue-emission exciplex-based organic light-emitting diodes. In addition, the device with the quantum well structure exhibited purer blue-light emission, and the color temperature stability was also highly improved.

Nonconjugated Triptycene-Spaced Donor-Acceptor-Type Emitters Showing Thermally Activated Delayed Fluorescence via Both Intra- and Intermolecular Charge-Transfer Transitions.

Thermally activated delayed fluorescence (TADF) emitters have aroused considerable attention, particularly for their great potential in organic light-emitting diodes (OLEDs). In typical TADF molecules, intramolecular charge transfer (CT) between electron-donor (D) and electron-acceptor (A) moieties is the dominant transition. Actually, CT transitions can possibly occur between different molecules as well. Herein, we used a nonconjugated triptycene (TPE) moiety to space D and A moieties and developed two novel emitters tBuDMAC-TPE-TRZ and tBuDMAC-TPE-TTR to explore the roles of intra- and intermolecular CT transitions. Along with weak intramolecular CT transitions, intermolecular CT transitions are dominant for tBuDMAC-TPE-TRZ and tBuDMAC-TPE-TTR neat films. Particularly, tBuDMAC-TPE-TRZ showed a high maximum external quantum efficiency of 10.0% in a nondoped solution-processed OLED, which was evidently higher than that of a corresponding 10 wt % tBuDMAC-TPE-TRZ-doped OLED with 4,4',4″-tris(carbazol-9-yl)triphenylamine (TCTA) as the host matrix. The results prove that intermolecular CT transitions indeed participate in the CT transition process in these systems and they are helpful to enhance the electroluminescence performance of emitting systems with weak intramolecular CT transitions.

Carrier transport regulation with hole transport trilayer for efficiency enhancement in quantum dot light-emitting devices

Due to deep valence energy level of colloidal quantum dots (QDs), it's challenge to achieve efficient hole injection from organic function materials to QDs. To improve hole injection, hole transport trilayer (HTTL), consisting of 4,4′-bis(N-carbazolyl)-1,1′-biphenyl (CBP)/4,4′,4″-tris(carbazol-9-yl) triphenylamine (TCTA)/di-[4-(N,N-di(p-tolyl)-amino)-phenyl]cyclohexane (TAPC) is introduced into inverted quantum dot light-emitting devices (QLEDs). Due to the formation of cascade energy levels, the HTTL is expected to facilitate hole injection, decrease hole accumulation at QDs/hole transport layer (HTL) interface and reach better carrier balance. As a result, compared with control device without cascade energy levels, 64% enhancement in device performances is achieved for the optimized green QLED with cascade energy levels. It is proved that the reduced holes accumulation and improved carrier balance are the main reasons for the considerable efficiency enhancement.

Effects of in-situ annealing on the electroluminescence performance of the Sn-based perovskite light-emitting diodes prepared by thermal evaporation

The Sn-based perovskite light-emitting diodes (PeLED) with the structure of (ITO)/MoO3/4,4′-cyclohexylidenebis[N,N-bis(p-tolyl)aniline](TAPC)/4,4′,4′-Tris(carbazol-9-yl)-triphenylamine (TCTA)/perovskite/1,3,5-Tri(m-pyrid-3-yl-phenyl)benzene (TmPyPB)/lithium fluoride(LiF)/Al were fabricated by thermal evaporation and in-situ annealing. The perovskite emitting layers were annealed at the various temperature of 50, 75 and 85 °C during the dual sources thermal evaporation of CsBr and SnBr2 instead of routine post-synthetic annealing for the formation of crystalline CsSnBr3 film. The effects of annealing temperature on the morphology, structure and photophysical properties of the CsSnBr3 perovskite films as well as the electroluminescence(EL) performance of the PeLED were investigated. Little temperature dependence of perovskite emitting layers' morphology was found while obviously intensified absorbance, crystallinity and steady-state photoluminesce(PL) as well as apparently increased PL decay lifetime and slight red-shifted PL spectra of the CsSnBr3 perovskite films upon increasing in-situ annealing temperature were demonstrated. The similar temperature dependent behavior of steady-state PL intensity, transient PL decay life time and photoluminescence quantum yield(PLQY) of all the CsSnBr3 films verified that the hybrid effect of suppressed deep acceptor states and enhanced emitting from shallow trap states would be responsible for the PL behavior of in-situ annealed CsSnBr3 films. In-situ annealing was also capable of extending carriers lifetime and reducing trap density, and leading to the occurrence of the suppressed “self-doping” of Sn4+ and reduction of acceptor states. Meanwhile, the improved crystal quality of the CsSnBr3 nanocrystals should be closely related to the enhanced charge carriers dynamics and improved PL performance. The PeLED with 85 °C in-situ annealed CsSnBr3 emitting layer demonstrated optimal EL performance with the current efficiency(CE) of 0.34 cd/A and external quantum efficiency(EQE) of 0.16%, which was consistent with the annealing temperature dependence of PL behavior of the CsSnBr3 perovskite emitting layer and could be attributed to its superior PL performance, low trap density and high crystallinity.

In Situ Electropolymerization Enables Ultrafast Long Cycle Life and High-Voltage Organic Cathodes for Lithium Batteries.

Organic cathode materials have attracted extensive attention because of their diverse structures, facile synthesis, and environmental friendliness. However, they often suffer from insufficient cycling stability caused by the dissolution problem, poor rate performance, and low voltages. An in situ electropolymerization method was developed to stabilize and enhance organic cathodes for lithium batteries. 4,4',4''-Tris(carbazol-9-yl)-triphenylamine (TCTA) was employed because carbazole groups can be polymerized under an electric field and they may serve as high-voltage redox-active centers. The electropolymerized TCTA electrodes demonstrated excellent electrochemical performance with a high discharge voltage of 3.95 V, ultrafast rate capability of 20 A g-1 , and a long cycle life of 5000 cycles. Our findings provide a new strategy to address the dissolution issue and they explore the molecular design of organic electrode materials for use in rechargeable batteries.

Optimized trade-off between electroluminescent stability and efficiency in solution-processed WOLEDs adopting functional iridium(III) complexes with 9-phenyl-9-phosphafluorene oxide (PhFlPO) moiety

Employing complimentary color phosphorescent emitters of the well-known FIrpic and new unsymmetrical orange emitter Ir-POB with 9-phenyl-9-phosphafluorene oxide (PhFlPO) moiety, solution-processed white organic lighting-emitting diodes (WOLEDs) had been fabricated to cope with the variation of EL spectra at different working voltage through excitation of both FIrpic and Ir-POB with the same mechanism in the device. Through constructing a thin exciton formation zone by the energy level layout between host 4,4′,4″-tris(carbazol-9-yl)triphenylamine (TCTA) and 1,3,5-tris-(N-(phenyl)-benzimidazole)-benzene (TPBi), both FIrpic and Ir-POB in the single emission layer can be excited by energy-transfer mechanism to bring stable white EL spectra in wide range of driving voltages with small CIE coordinate variation of Δx = 0.0044 and Δy = 0.0197. Furthermore, in order to overcome the disadvantage associated with energy-transfer mechanism, both FIrpic and Ir-POB have been excited by direct charge-trapping mechanism in WOLEDs by judiciously controlling the energy level layout between phosphorescent emitters and co-hosts polyvinyl carbazole (PVK) and 1,3-bis(5-(4-(tert-butyl)phenyl)-1,3,4-oxadiazol-2-yl)benzene (OXD-7). The concerned WOLEDs not only maintain stable white EL in even wider driving voltage rang with CIE coordinate variation of Δx = 0.0078 and Δy = 0.0053, but also furnish much higher EL efficiencies of maximum external quantum efficiency (ηext) of 22.4%, a maximum current efficiency (ηL) of 58.4 cd A−1 and a maximum power efficiency (ηP) of 41.3 lm W−1. Hence, by unifying excitation mechanism of the phosphorescent emitters, optimized trade-off between white EL stability and high EL efficiencies have been successfully achieved. Definitely, these results can provide crucial information for developing WOLEDs with high performances.

In Situ Electropolymerization Enables Ultrafast Long Cycle Life and High‐Voltage Organic Cathodes for Lithium Batteries

AbstractOrganic cathode materials have attracted extensive attention because of their diverse structures, facile synthesis, and environmental friendliness. However, they often suffer from insufficient cycling stability caused by the dissolution problem, poor rate performance, and low voltages. An in situ electropolymerization method was developed to stabilize and enhance organic cathodes for lithium batteries. 4,4′,4′′‐Tris(carbazol‐9‐yl)‐triphenylamine (TCTA) was employed because carbazole groups can be polymerized under an electric field and they may serve as high‐voltage redox‐active centers. The electropolymerized TCTA electrodes demonstrated excellent electrochemical performance with a high discharge voltage of 3.95 V, ultrafast rate capability of 20 A g−1, and a long cycle life of 5000 cycles. Our findings provide a new strategy to address the dissolution issue and they explore the molecular design of organic electrode materials for use in rechargeable batteries.

Improved device performance of solution-processed red-colored Cu–In–Zn–S-based quantum dot light-emitting diodes enabled by doping TCTA into the emitting layer

The working mechanisms in the cadmium-free Cu–In–Zn–S(CIZS)-based quantum dot light-emitting didoes (QD-LEDs) were reported in previous reports, which were mai nly determined by the direct charge injection or the energy transfer. In this paper, we presented an improved device performance in solution-processed red-colored CIZS-based QD-LEDs by doping a small molecule 4,4′,4″-tris-(carbazol-9-yl)- triphenylamine (TCTA) into the emitting layer, and the best peak current efficiency of 3.22 cd A−1 and maximum luminance (Lmax) of 2679 cd m−2 could be achieved by optimizing the doping percentage of TCTA in the CIZS/ZnS nanocrystals (NCs). Such red-colored QD-LEDs exhibited a 210% increase in the current efficiency and no obvious change in the electroluminescence (EL) spectra as compared with the QD-LEDs without TCTA. The improvement of the device performance could be attributed to the synergistic effects of more balanced hole injection and the effective exciton energy transfer from TCTA to the NCs. The balanced hole injection could be verified by the fact that an increased current efficiency in the QD-LEDs by doping TCTA into an organic hole-transport layer.

Enhanced efficiency and stability of organic light-emitting diodes via binary self-assembled monolayers of aromatic and aliphatic compounds on indium tin oxide

Abstract Regulating hole injection via self-assembled monolayers (SAMs) modification on indium tin oxide (ITO) is significantly favourable for achieving high efficiency and stability of organic light-emitting diodes (OLEDs). In this work, ITO was modified by pentafluorobenzylphosphonic acid (F5BnPA) and heneicosafluorododecylphosphonic acid (HF21DPA) in a binary SAMs way. By altering mole ratios of these two materials, ITO work function can be achieved from 5.20 to 5.82 eV and the roles of F5BnPA and HF21DPA in affecting hole injection and device performances were also explored. The results demonstrate a synergistic effect that HF21DPA improves ITO work function efficiently for its fluorinated alkyl chain and F5BnPA enhances the charge transfer directly due to its aromatic group gathering HOMO level. When α-naphthylphenylbiphenyldiamine (NPB) and 4,4′,4″-tris(carbazol-9-yl) triphenylamine (TCTA) were used as hole transport layers (HTLs) in OLEDs with a structure of ITO/SAM/HTL/tris(8-hydroxyquinolino) aluminum (III) (Alq3)/lithium fluoride (LiF)/Al, brightness up to 36839 and 58189 cd/m2 and current efficiency up to 5.75 and 7.35 cd/A were obtained, respectively. Furthermore, the influence of binary SAMs on the stability of NPB-based OLEDs was studied. The maximum half-lifetime at the initial brightness of 2200 cd/m2 reaches 368.0 h, which is 75.1 times that of the poly(3, 4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)-containing device. The high durability is attributed to higher hydrophobicity and lower hole injection barrier caused by SAMs. This is the first report on the synergistic effect of aromatic and aliphatic compounds in binary SAMs on regulating hole injection, showing a new approach of obtaining high efficiency and stability of OLEDs.

Exciplex‐Based Organic Light‐Emitting Diodes with Near‐Infrared Emission

AbstractNear‐infrared exciplex can weaken molecular design difficulties, and has the advantage of easy bathochromic‐shift spectra via selecting the suitable electron donors and acceptors. In this contribution, exciplex is applied to fabricate near‐infrared (NIR) organic light‐emitting diodes (OLEDs) incorporating a synthesized fluorescent material 3‐([1,1″:3′,1″‐terphenyl]‐5′‐yl)acenaphtho[1,2‐b]pyrazine‐8,9‐dicarbonitrile (APDC‐tPh) and a commercially available material 4,4′,4″‐tris(carbazol‐9‐yl)triphenylamine (TCTA). The device having a mixed TCTA:APDC‐tPh as an emitting layer shows a 730 nm NIR emission with a maximum external quantum efficiency (EQE) of about 0.1%, while the device having 2‐[4‐(diphenylamino)phenyl]‐10,10‐dioxide‐9H‐thioxanthen‐9‐one (TXO‐TPA):APDC‐tPh as the emitting layer exhibits an emission peak of 704 nm with a maximum EQE of 1.27%. These results prove the feasibility of fabricating the efficient exciplex‐based NIR OLEDs.

Investigation of charge-transporting layers for high-efficiency organic light-emitting diode

In the present work, we study a comprehensive model to quantitatively investigate the role of charge-transporting materials on exciton recombination and electric field distribution across the emissive and electron-transporting layers in organic light-emitting diode (OLED) devices via electrical simulation. The devices are composed of 4,4′,4″-tris(carbazol-9-yl)triphenylamine (TCTA) and 4,4′-bis(carbazol-9-yl) biphenyl (CBP) hosts, bathophenanthroline (Bphen) and 2,2′,2″-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole) (TPBi) as electron-transporting materials (ETMs), and 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC) as a hole-transporting material. The outcomes reveal that the recombination rate across the emissive layer (EML) is highly influenced by the charge carrier mobility of ETMs. The Bphen-based device exhibits a maximum recombination rate of 3.5 × 106 cm−3 s−1, which is 105 times higher than that of the TPBi-composed device. The recombination rate is increased by two orders of magnitude by incorporating a TAPC for the hole transport layer. It is increased from 1.9 × 106 to 3.5 × 106 cm−3 s−1 as the host is changed from TCTA to CBP. Meanwhile, the electric field distribution is decreased from 0.28 to 0.17 MV cm−1 across the TCTA EML in the presence of the hole transport layer, but is increased 0.36 MV cm−1 when TCTA EML is replaced with CBP. Experimentally, the Bphen-based device exhibits a power efficiency of 12.5 lm W−1 and an external quantum efficiency of 5.1%, which are higher than those of the TPBi counterpart.

Influence of heat treatment on hole transfer dynamics in core-shell quantum dot/organic hole conductor hybrid films

The influence of heat treatment on hole transfer (HT) processes from the CdSe/ZnS and CdSe/CdS/ZnS quantum dots (QDs) to 4,4[Formula: see text],4[Formula: see text]-Tris(carbazol-9-yl)-triphenylamine (TCTA) in QD/TCTA hybrid films has been researched with time-resolved photoluminescence (PL) spectroscopy. The PL dynamic results demonstrated a heat-treatment-temperature-dependent HT process from the core-shell CdSe QDs to TCTA. The HT rates and efficiencies can be effectively increased due to reduced distance between core-shell CdSe QDs and TCTA after heat treatment. The CdS shell exhibited a more obvious effect on HT from the core-shell CdSe QDs to TCTA than on electron transfer to TiO2, due to higher barrier for holes to tunnel through CdS shell and larger effective mass of holes in CdS than electrons. These results indicate that heat treatment would be an effective means to further optimize solid-state QD sensitized solar cells and rational design of CdS shell is significant.

Two-dimensional-growth small molecular hole-transporting layer by ultrasonic spray coating for organic light-emitting devices

Two-dimensional-growth small molecular organic thin film with high quality is fabricated by ultrasonic spray coating technology (USC) from the toluene solution of 4,4′,4″-tris (carbazol-9-yl) triphenylamine (TCTA). In comparison to the vacuum thermal evaporation (VTE) TCTA film, the USC-TCTA film obtained from liquid-phase solution possesses more uniform surface topography. The differences between the USC-TCTA and the VTE-TCTA in optical property, electrical property and formation mechanism are also studied in detail. Besides, to evaluate the hole transport and electron blocking ability of USC-TCTA film, the organic light-emitting devices (OLEDs) employing USC-TCTA film as hole transport layer are fabricated successfully. Additionally, the green OLEDs based on USC-TCTA film perform as well as the ones with VTE-TCTA film in current density, luminance, efficiency and color stability, and show even better tolerance to high bias voltage.