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• Decreasing the carrier density of exciton formation zone benefits the stability of organic light-emitting diodes for electrically pumped organic lasers. • The carrier density has been modeled under high current injection via the model of carrier device lifetimes. • The carrier density decreases with the emissive layer's thickness increasing, but increases with the emissive layer's charge carrier mobilities. • The increase of the energetic disorder of emissive layer leads to a marked decrease of carrier density. • Increasing the charge carrier mobilities of hole and electron transport layers helps reduce carrier density. The carrier density in exciton formation zone is the electrical parameter most relevant to the stability of organic light-emitting diode: the decrease of carrier density improves the device stability. Here, based on the general mode of carrier device lifetimes, the carrier densities in the exciton formation zone of organic light-emitting diode have been calculated at current densities (J) ≥ 2.0 kA cm−2. With J increasing, the carrier density increases accordingly. At a given J , the carrier density decreases with the emissive layer's thickness increasing, but increases with the emissive layer's charge carrier mobilities. The increase of the energetic disorder of emissive layer leads to a marked decrease of carrier density. Increasing the hole (electron) mobility of hole (electron) transport layer helps reduce carrier density. The current research is believed very beneficial to the development of electrically pumped organic lasers. [ABSTRACT FROM AUTHOR]

Organic light emitting diodes using a mixed layer of electron acceptor 3, 4, 9, 10 perylenetetracarboxylic dianhydride and electron donor copper phthalocyanine (PTCDA:CuPc) on indium tin oxide (ITO) anodes were fabricated. The device properties were found to be strongly dependent on the thickness of the PTCDA:CuPc film: both the power efficiency and the driving voltage of the device were optimized with a thickness of PTCDA:CuPc ranging from 10 to 20 nm. As compared to the conventional ITO/CuPc hole injection structure, the ITO/PTCDA:CuPc hole injection structure could remarkably enhance both the luminance and the power efficiencies of devices. A mechanism of static-induced, very efficient hole-electron pairs generation in mixed PTCDA:CuPc films was proposed to explain the experimental phenomena. The structural and optical properties of PTCDA:CuPc film were examined as well. [ABSTRACT FROM AUTHOR]

Electron-transporting small molecule bathophenanthroline (Bphen) together with o-xylene has been used as hybrid additives to improve the performance of simplified inverted polymer solar cells employing ITO alone as cathode and photoactive layer based on polymer [[2,6′-4,8-di(5-ethylhexylthienyl)benzo[1,2-b;3,3-b] dithiophene] [3-fluoro-2[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]] (PTB7-Th) and (He et al., Nat. Photon. 9:174, 2015)-phenyl C-butyric acid methyl ester (PCBM). Because the Bphen additive could spontaneously aggregate onto the indium tin oxide (ITO) cathode during spin coating, the mixed solution containing PTB7-Th, PCBM, and Bphen, thereby forming a thin cathode-modifying layer, the ternary blend PTB7-Th:PCBM:Bphen functioned similar to a layered polyethylenimine ethoxylated (PEIE, a conventional cathode-modifying material)/binary blend PTB7-Th:PCBM combination. The o-xylene additive was confirmed to enrich the distribution of PTB7-Th donor towards the bottom area of photoactive layer, thereby benefiting the charge collection in inverted structure. With the o-xylene optimization, the PTB7-Th:PCBM:Bphen blend thin film showed a power conversion efficiency (PCE) of 5.87% in simplified inverted structure of ITO/photoactive layer/MoO/Ag, much higher than that (4.21%) of the PTB7-Th:PCBM blend thin film. The current research can be considered as a useful attempt towards fabricating low-cost photovoltaic devices without marked loss in PCE. [ABSTRACT FROM AUTHOR]

The doped organic/organic p-n heterojunctions have been applied as charge generation structure (CGS) in tandem organic light emitting diodes (TOLEDs). It is found that the field-induced charge generation takes place more efficiently at the interface between Li2CO3 n-doped bathocuproine (BCP:Li2CO3) and MoO3 p-doped 4,4′- N, N′-dicarbazole-biphenyl (CBP:MoO3) than at the interface between BCP:Li2CO3 and MoO3 p-doped 4,4-bis[ N-1-naphthyl- N-phenylamino]biphenyl (NPB:MoO3). It is because the process of electrons tunneling through the depletion zone from the highest occupied molecular orbit (HOMO) of CBP:MoO3 to the lowest unoccupied molecular orbit (LUMO) of BCP:Li2CO3 is more efficient than that from the HOMO of NPB:MoO3 to the LUMO of BCP:Li2CO3. Compared to the TOLED using the conventional CGS of 10-nm BCP:Li2CO3/20-nm NPB:MoO3, the one using the CGS of 10-nm BCP:Li2CO3/10-nm CBP:MoO3/10-nm NPB:MoO3 shows increased device performance. In addition, the interconnecting property of CGS of 10-nm BCP:Li2CO3/ x nm CBP:MoO3/20 − x nm NPB:MoO3 shows a strong dependence on the thickness of CBP:MoO3. We provide a new insight on optimizing Ohmic loss in the CGSs, useful for improving the performance of TOLEDs. [ABSTRACT FROM AUTHOR]

• The width of exciton formation zone decreases with device current density increasing. • The width of exciton formation zone increases with emissive layer's thickness increasing. • An optimal charge mobility of emissive layer maximizes the width of exciton formation zone. • The width of exciton formation zone has certain correlation with the dielectric constant of emissive layer. • The width of exciton formation zone markedly increases with emissive layer's trap density increasing. The width of exciton formation zone has been simulated in a single-layer organic light emitting diode (OLED) based on the model of carrier device lifetimes. The width of exciton formation zone decreases with device current density increasing. Increasing the thickness of emissive layer (EML) is able to widen exciton formation zone. There is an optimal value of EML's charge carrier mobility to maximize the width of exciton formation zone. In addition, the width of exciton formation zone increases markedly with the trap density of EML increasing, and shows certain correlation with the dielectric constant of EML. The current modeling provides novel insights on optimizing EMLs towards wide exciton formation zone, helpful for extending operational stability of OLED. [ABSTRACT FROM AUTHOR]

The MoO 3 doped N,N′-bis-(1-naphthyl)-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB:MoO 3 in 2:1 mass ratio) and 4,4′-N,N′-dicarbazole-biphenyl (CBP:MoO 3 in 2:1 mass ratio) as p -doped hole transport layers have been used in inverted organic light emitting diodes (IOLEDs). Compared to the NPB/20 nm NPB:MoO 3 structure, the NPB/10 nm CBP:MoO 3 /10 nm NPB:MoO 3 structure showed increased device performance, mostly because the hole transport barrier from CBP:MoO 3 to NPB was smaller than that from NPB:MoO 3 to NPB; it also presented improved device performance than the NPB/20 nm CBP:MoO 3 structure, ascribed to the higher conductivity of NPB:MoO 3 than that of CBP:MoO 3 . We provide a manageable way to unlock the merits of p -doped hole transport layers for markedly increasing the performance of IOLEDs. [ABSTRACT FROM AUTHOR]

The performance of inverted organic light-emitting diodes (IOLEDs) has been improved based on MoO-doped N,N′-bis-(1-naphthyl)-diphenyl-1,1′-biphenyl-4,4′-diamine (2:1 NPB:MoO in mass ratio) and 4,4′-N,N′-dicarbazole-biphenyl (2:1 CBP:MoO in mass ratio). The sandwiched- p-doped-layer hole injection structure of CBP:MoO 10 nm/NPB:MoO 5 nm/CBP:MoO 5 nm/Al showed increased device performance via enhancing hole current into the CBP, compared to the single- p-doped-layer hole injection structure of CBP:MoO 20 nm/Al, mostly due to the higher conductivity of NPB:MoO than that of CBP:MoO; it also improved device current and thereby performance than the double- p-doped-layer hole injection structure of CBP:MoO 10 nm/NPB:MoO 10 nm/Al, mostly attributed to that the hole injection from Al to CBP:MoO was more efficient than that from Al to NPB:MoO. The current research provides some insights in reducing the power loss toward the commercialization of IOLEDs. [ABSTRACT FROM AUTHOR]

The inverted organic light-emitting diodes (IOLEDs) have been fabricated using the hybrid- p-doped hole transport layer consisting of MoO-doped N, N′-bis-(1-naphthl)-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB:MoO) and 2,3,5,6-Tetrafluoro-7,7,8,8,-tetracyano-quinodimethane-doped NPB (NPB:F-TCNQ). Compared with the IOLED using the 20 nm NPB:MoO/Al, the one using the 10 nm NPB:F-TCNQ/10 nm NPB:MoO/Al showed increased performance, attributed to the higher conductivity of NPB:F-TCNQ than NPB:MoO, reducing the ohmic loss in hole conduction through the combined 10 nm NPB:F4-TCNQ and 10 nm NPB:MoO than through the 20 nm NPB:MoO; it also presented improved performance than the IOLED using the 20 nm NPB:F-TCNQ/Al, ascribed to the non-ohmic contact formation between NPB:F-TCNQ and Al, resulting from that the p-doping effect of F-TCNQ in NPB was significantly suppressed by the Al deposition in the interfacial zone. The hybrid p-doping of hole transport layer can offer a large space to promote the performance of IOLEDs. [ABSTRACT FROM AUTHOR]

The hole-injecting structure of 15 nm MoO-doped 4,4- N, N-bis [ N-1-naphthyl- N-phenyl-amino]biphenyl (NPB:MoO)/5 nm MoO-doped 4,4′- N, N′-dicarbazole-biphenyl (CBP:MoO) has been used in organic light emitting diodes (OLEDs). It was found that a device using the 15 nm NPB:MoO/5 nm CBP:MoO/NPB combination was superior to one adopting the 20 nm NPB:MoO/NPB combination due to two major causes: the NPB:MoO/CBP:MoO interface is a quasi-ohmic contact, and the hole transport barrier from CBP:MoO to NPB is smaller than that from NPB:MoO to NPB; moreover, it outperformed the device employing the 20 nm CBP:MoO/NPB combination, mostly because of the higher conductivity of NPB:MoO compared to CBP:MoO. We demonstrate that using a structure resulting from uniting two p-doped hole transporters is a beneficial, simple method of achieving an improved trade-off between high conductivity and small hole transport barrier, thereby leading to a significantly reduced ohmic loss in the hole current conduction in the OLEDs, relative to the single p-doped layers. [ABSTRACT FROM AUTHOR]

The combination of MoO3-doped 4,4- N, N- bis [ N-1-naphthyl- N-phenyl-amino]biphenyl (NPB:MoO3) and 4,4′- N, N′-dicarbazole-biphenyl (CBP:MoO3) was used to enhance the hole conduction in organic light-emitting diodes (OLEDs). It is found that the OLED using NPB:MoO3 10 nm/CBP:MoO3 5 nm showed a much increased current density than the one using NPB:MoO3 5 nm/CBP:MoO3 5 nm at a given voltage larger than 4 V, mainly because the hole transport barrier across the p-doped heterojunction in the former device became smaller than that in the latter device with the driving voltage increasing, despite the fact that the 10-nm NPB:MoO3 in the former device caused more Ohmic loss than the 5-nm one in the latter device. As a result of the higher conductivity of NPB:MoO3 than that of CBP:MoO3, the OLED using the combination of 15-nm NPB:MoO3 and 5-nm CBP:MoO3 showed significantly increased performance than the one using the single 20-nm CBP:MoO3. We provide a useful way of advancing the OLEDs toward the practical applications in general lighting and flat-panel displays. [ABSTRACT FROM AUTHOR]

We report the manageable formation of the gradient-layered poly(3-hexylthiophene) and [6,6]-phenyl C61-butyric acid methyl ester (P3HT/PCBM) blend film by spin coating via introducing bathocuproine (BCP) into the mixed P3HT/PCBM solution. The BCP can improve the aggregation and thereby the preferential precipitation of PCBM during the spin-coating process, leading to the gradient-layered phase separation of P3HT and PCBM. The regular solar cells using the gradient-layered ternary blend films gave poor photovoltaic performance, due to the mismatch between the polarity of the regular-device structure and the vertical composition profile of the ternary blend film. By contrast, in the inverted solar cell, the gradient-layered ternary blend film could provide the increased device performance over the conventional bulk heterojunction binary blend films. [ABSTRACT FROM AUTHOR]

A white organic light-emitting diode with the structure of ITO/NPB 30 nm/TCTA+2% TPP 20 nm/BCP+0.4% Ir(piq)320 nm/Alq3 40 nm/Mg:Ag was fabricated and characterized, where 2,5,7,10-tetra-phenylpyrene and tris(1-phenylisoquinoline) iridium (III) [Ir(piq)3] were used as a blue fluorescent dye and a red phosphorescent dye respectively. The I–V characteristics of the device showed a turn-on voltage of 2.6 V. The electroluminescent spectra of the device consisted of blue fluorescent and red phosphorescent emissions. The intensity of the blue emission increased gradually relative to the red emission with increasing voltage. The emissions of the device were in the white-light region between 10 and 15 V. A maximum white light luminance of 1076 cd/m2 with CIE coordinates of (x, y=0.27, 0.24) was reached at 15 V with an efficiency of 1.35 cd/A. The white light emission is related to the simultaneous exciton formation on both sides of the TCTA/BCP interface. [ABSTRACT FROM AUTHOR]

Blue phosphorescent organic light-emitting diodes (B-PHOLEDs) using host–guest emissive layers have been studied, where the host and guest are 2,6-bis(3-(9H-carbazol-9-yl)phenyl)pyridine (26DCzPPy) and bis[2-(4,6-difluorophenyl)pyridinato-C2,N](picolinato)iridium(III) (FIrPic), respectively. For the emissive layer with dye (guest) concentration of either 3 mol% or 10 mol%, there exist both the major and minor effective bandgaps. The major effective bandgap is governed by the lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) levels of 26DCzPPy, because the host molecules form a major dynamic-favorable channel to transport charge carriers. The minor effective bandgap is governed by the LUMO and HOMO levels of FIrPic, since the guest molecules form a minor thermodynamic-favorable channel to transport charge carriers. For the emissive layer with dye concentration of 22 mol%, the effective bandgap is determined by the LUMO and HOMO levels of FIrPic, because the guest molecules form a both dynamic- and thermodynamic-favorable channel to conduct charge carriers. Although the B-PHOLED with emissive layer of 26DCzPPy:FIrPic (3 mol%) shows wider exciton formation zone than the one with emissive layer of 26DCzPPy:FIrPic (10 mol%), the latter gives higher stability than the former, mostly attributed to the shorter triplet lifetime of 26DCzPPy:FIrPic (10 mol%) than that of 26DCzPPy:FIrPic (3 mol%). Due to both the larger effective bandgap and more charge carrier traps, the emissive layer of 26DCzPPy:FIrPic (10 mol%) enlarges the exciton formation zone and thereby increases device stability than that of 26DCzPPy:FIrPic (22 mol%), despite that the former has the longer triplet lifetime than the latter. The current research provides some novel insights into the correlation of dye-based nanoarchitectonics (dye concentration) with the device performance, helpful for the commercial development of B-PHOLEDs using host–guest emissive layers. [ABSTRACT FROM AUTHOR]

Inverted organic solar cells have been fabricated with an anode modifying bilayer, comprised of thermally evaporated MoO3 and ytterbium n-doped bathocuproine (BCP:Yb). In the bilayer, MoO3 and BCP:Yb play the roles of forming ohmic contacts with photoactive layer and anode, respectively; due to the Fermi level alignment, MoO3 and BCP:Yb form a low-barrier interface, benefiting hole injection and extraction. The MoO3/BCP:Yb bilayer enables higher open-circuit voltage of inverted device than the conventional MoO3 layer, mostly because BCP:Yb suppresses the reduction of MoO3 work function by anode. Moreover, the introduction of BCP:Yb helps increase the optical absorption of inverted device and thereby short-circuit current density. Although BCP:Yb gives increased electron mobility than MoO3, the MoO3/BCP:Yb bilayer decreases hole mobility of inverted device and thereby fill factor than the MoO3 layer, mostly due to the interfacial p-doping effect of MoO3 on BCP:Yb. The power conversion efficiency based on MoO3/BCP:Yb bilayer is 6.60%, higher than that (6.25%) based on the MoO3 layer. The current research indicates that n-doped organic layers are helpful to improve the efficiencies of inverted OSCs via assisting the anode modification. [ABSTRACT FROM AUTHOR]

Organic solar cells (OSCs) have been developed using aluminum-doped bathocuproine (BCP:Al) as cathode-modifying layer. Although BCP:Al thin film shows decreased electron mobility than neat BCP thin film, the former is advantageous over the latter in the following two aspects. Firstly, BCP:Al has more gap states, offering more efficient electron injection and extraction at the interface with electron acceptor, thereby contributing to the increase in fill factor. Secondly, BCP:Al increases the optical absorption of device, contributing to the increase in short-circuit current density. As a result, the OSC based on BCP:Al shows improved power conversion efficiency than that based on neat BCP. Moreover, the former device presents increased thermal stability than the latter, mostly because doped Al clusters can inhibit the aggregation tendency of BCP molecules. We provide a novel insight to fabricate cost-effective cathode-modifying layers, useful for pushing forward the commercialization of OSCs. [ABSTRACT FROM AUTHOR]

Inverted fullerene organic solar cells with cathode modifying layers (CML) of ZnO/electron acceptor/polyethylenimine ethoxylated (PEIE) are fabricated, where electron acceptor is either [6,6]‐phenyl C71‐butyric acid methyl ester (PC71BM) or a nonfullerene acceptor (IDIC). Compared to the devices based on conventional ZnO and ZnO/PEIE, the ones based on ZnO/PC71BM/PEIE and ZnO/IDIC/PEIE show increased short‐circuit current densities (JSC), demonstrating both PC71BM and IDIC interlayers enhance the exciton splitting in donor phase located at the bottom of photoactive layer. The nearly same values of JSC based on ZnO/PC71BM/PEIE and ZnO/IDIC/PEIE imply the PC71BM and IDIC interlayers have almost identical capabilities of splitting excitons in donor phase, governed by the quadrupolarities and stacking modes of electron acceptors. The PC71BM and IDIC interlayers passivate the oxygen‐deficient defects of ZnO surface, leading to the increases in fill factor (FF) of device; the ZnO/IDIC/PEIE gives larger FF than the ZnO/PC71BM/PEIE, indicating IDIC passivate ZnO more effectively than PC71BM. The current research provides some helpful insights into developing high‐performance electron acceptors. [ABSTRACT FROM AUTHOR]

Phosphorescent organic light emitting diodes (PHOLEDs) have been fabricated with structure of indium tin oxide/MoO3 doped 4,4′-N,N'-dicarbazole-biphenyl (CBP) 30 nm/tris(4-carbazoyl-9-ylphenyl)amine 10 nm/CBP doped with tris(2-phenylpyridine)iridium(III) (CBP:Ir(ppy)3) x/bathocuproine 50 nm/LiF 1 nm/Al, where x = 2.5, 5, 10, and 20 nm, respectively. The current efficiency (CE) of device with x = 10 nm is higher than those with x = 2.5 and 5 nm, mostly because the width of exciton formation zone (5.7 nm) with x = 10 nm is larger than those (2.5 and 5 nm) with x = 2.5 and 5 nm. However, the current density with x = 10 nm decreases than those with x = 2.5 and 5 nm at a certain driving voltage, since the ~ 4.3 nm CBP:Ir(ppy)3 accommodating no exciton formation with x = 10 nm plays a role of transporting holes, raising ohmic loss of hole and thereby increasing driving voltage. When x increases from 10 to 20 nm, the width of exciton formation zone rises from 5.7 to 6.8 nm with CE almost unchanged, and the current density decreases as a result of increased ohmic loss of hole. The current research is useful to develop high-efficiency and low-driving voltage PHOLEDs. [ABSTRACT FROM AUTHOR]

Organic light emitting diodes (OLEDs) have been fabricated using various p -doped hole injection structures based on MoO 3 doped 4,4′- N , N′ -dicarbazole-biphenyl (CBP:MoO 3 ) and 2,3,5,6-Tetrafluoro-7,7,8,8,-tetracyano-quinodimethane doped 4,4-bis[ N -1-naphthyl- N -phenylamino]biphenyl (NPB:F 4 -TCNQ). It is found that the hole injection from indium tin oxide (ITO) to CBP:MoO 3 is more efficient than that from ITO to NPB:F 4 -TCNQ, although the CBP:MoO 3 is much less conductive than the NPB:F 4 -TCNQ. In addition, the CBP:MoO 3 is helpful to block F 4 -TCNQ from diffusing into the emissive zone and thereby relieve the exciton quenching induced by organic p -dopant. Thus, the improved hole injection structure of ITO/10 nm CBP:MoO 3 /5 nm NPB:F 4 -TCNQ/5 nm CBP:MoO 3 is provided to diminish the hole and exciton losses, greatly increasing the device performance than the other hole injection structures. The current research is believed beneficial for the development of OLEDs based on a p-i-n junction. [ABSTRACT FROM AUTHOR]

• The exciton-blocking capability of charge blocking layer governs the device efficiency. • The carrier mobility of charge blocking layer governs the device stability. • The carrier mobility of charge blocking layer governs the width of exciton formation zone. • The carrier device lifetimes underpins the width of exciton formation zone. Blue thermally activated delayed fluorescence organic light-emitting diodes (OLEDs) have been fabricated using engineered charge blocking layers. It is found that the device efficiency increases with increasing the exciton blocking capability of electron blocking layer. But the device stability decreases concomitantly, mostly because the hole mobility of electron blocking layer decreases with exciton blocking capability increasing, thereby leading to the smaller width of exciton formation zone. In addition, the device stability decreases with the electron mobility of hole blocking layer decreasing, despite nearly same exciton blocking capabilities, mainly because the width of exciton formation zone decreases with the electron mobility of hole blocking layer decreasing. The width of exciton formation zone is understood based on the transit times for holes from anode to exciton formation zone and for electrons from cathode to exciton formation zone. We provide some in-depth insight useful for the delicate design of fluorescent, phosphorescent, and thermally activated delayed fluorescence OLEDs. [ABSTRACT FROM AUTHOR]

The inverted polymer:fullerene solar cells with structure of ITO/TiO/P3HT:PCBM/MoO/Al have been fabricated, where P3HT and PCBM stand for poly (3-hexylthiophene) and [6,6]-phenyl C-butyric acid methyl ester, respectively. It is discovered that the P3HT:PCBM blend film manipulated into the improved stratification structure, characterized as P3HT crystallite-rich zone close to the top surface and PCBM constituent-rich zone adjacent to the bottom surface, can offer nearly the same power conversion efficiency of solar cell, compared to the one grown into the bulk heterojunction structure, characterized as the bicontinuous interpenetrating network of P3HT and PCBM. We provide an alternative insight to the morphology control of inverted polymer:fullerene solar cells. [ABSTRACT FROM AUTHOR]

Abstract: Stable transparent titania thin films were fabricated at room temperature by combining thenoyltrifluoroacetone (TTFA)-modified titanium precursors with amphiphilic triblock poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO, P123) copolymers. The obtained transparent titania thin films were systematically investigated by IR spectroscopy, PL emission and excitation spectroscopy and transmission electron microscopy. IR spectroscopy indicates that TTFA coordinates the titanium center during the process of hydrolysis and condensation. Luminescence spectroscopy confirms the in-situ formation of lanthanide complexes in the transparent titania thin film. TEM image shows that the in-situ formed lanthanide complexes were homogeneously distributed throughout the whole thin film. The quantum yield and the number of water coordinated to lanthanide metal center have been theoretically determined based on the luminescence data. [Copyright &y& Elsevier]

The warm white organic light-emitting diodes (WOLEDs) consisting of four emissive layers (EMLs) as well as pure WOLEDs consisting of three EMLs have been fabricated by using three primary color phosphors as emitters. Experimental results demonstrated that energy transfer between dopants, direct carriers' trapping and main recombination zone are all important factors in determining the performances of obtained devices. By precisely managing dopants' concentrations and emitting layers' thicknesses, we realized the optimized warm WOLED with a Commission Internationale de l'Eclairage coordinates (CIE x,y) of (0.388, 0.383), giving the highest current efficiency (η c) of 69.00 cd/A, power efficiency (η p) of 60.19 lm/W and external quantum efficiency (EQE) of 20.63%. Additionally, by increasing the proportion of blue emission, we also realized the pure WOLED (CIE x,y value is (0.331, 0.385)) giving 60.48 cd/A (EQE = 16.90%, CRI = 72.03) and 51.32 lm/W in highest η c and η p , respectively. Especially, the optimal warm and pure WOLEDs exhibited the superior color stability with small CIE discrepancies of (0.020, 0.003) and (0.022, 0.004) in the range of 1–10 mA/cm2, respectively. Efficient multi-light-emitting layers warm and pure white phosphorescent organic light-emitting diodes (WOLEDs) with excellent color stability were fabricated by using PQ 2 Ir (dpm) (PQ = phenylquinoly-N,C20', dpm = dipivaloylmethane), Ir (mppy) 3 (tris(2-(4-tolyl)-phenylpyridine)iridium) and FIrpic (iridium (III)bis [(4,6-difluorophenyl)pyridinato-N,C20'picolinate) as red, green and blue emitters, respectively. Image 1 • Efficient warm and pure white phosphorescent organic light-emitting diodes were designed and fabricated. • Efficient energy transfer and direct carriers' trapping helps to realize high performance WOLEDs. • Well-matched energy levels help to balance carriers' distribution. • The designed devices displayed greatly improved injection and transport of electrons. [ABSTRACT FROM AUTHOR]

• Increasing work function of p -doped layer increases open-circuit voltage. • Two combined p -doped layers increase fill factor. • Two combined p -doped layers increase short-circuit current density. • Two combined p -doped layers increase power conversion efficiency than single ones. Inverted organic solar cells (OSCs) have been fabricated using MoO 3 doped N,N' -bis-(1-naphthyl)-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB:MoO 3), MoO 3 doped 4,4′- N,N' -dicarbazole-biphenyl (CBP:MoO 3), and combined CBP:MoO 3 /NPB:MoO 3 as anode modifying layers (AMLs), respectively. The CBP:MoO 3 /NPB:MoO 3 /anode increases fill factor of device than the NPB:MoO 3 /anode and CBP:MoO 3 /anode, mostly because the former enhances hole injection into photoactive layer than the latter two. The CBP:MoO 3 /NPB:MoO 3 /anode and CBP:MoO 3 /anode increase open-circuit voltage of device than the NPB:MoO 3 /anode, due to the larger work function of CBP:MoO 3 than that of NPB:MoO 3. It is also found that combined CBP:MoO 3 /NPB:MoO 3 enhances short-circuit current density of device than single NPB:MoO 3 and CBP:MoO 3 , mainly ascribed to the fact that the former improves absorptance of device than the latter two. As a result, the CBP:MoO 3 /NPB:MoO 3 /anode improves power conversion efficiency of device than the NPB:MoO 3 /anode and CBP:MoO 3 /anode. We present a useful concept to develop high-performance AMLs for inverted OSCs. [ABSTRACT FROM AUTHOR]

MoO3p-doped 4,4′-N,N′-dicarbazole-biphenyl (CBP:MoO3) has been used as a hole extraction layer in inverted organic solar cells (OSCs). It is found that although the CBP:MoO3 shows reduced conductivity than the conventional hole extraction layer of MoO3, the CBP:MoO3 yields nearly the same quasi-Fermi level for holes in a photoactive layer as the MoO3 does. As a result, the open-circuit voltages of inverted OSCs based on CBP:MoO3 and MoO3 remain almost unchanged. When the thickness of hole extraction layer is ≤ 20 nm, the CBP:MoO3 can enable nearly the same short-circuit current density of inverted device but improved fill factor, in comparison to the MoO3, leading to the power conversion efficiency based on CBP:MoO3 higher than that based on MoO3. The results show that the CBP:MoO3 can act as an useful hole extraction material for fabricating high-efficiency inverted OSCs. [ABSTRACT FROM AUTHOR]

Inverted organic solar cells (OSCs) have been fabricated using the photoactive blend thin films based on regioregular poly(3-hexylthiophene) (P3HT), [6,6]-phenyl C61-butyric acid methyl ester (PCBM), and leuco-crystal violet (LCV). It was found that the LCV as an efficient n-dopant could significantly increase intrinsic electron concentration of PCBM zone. The electron mobility of P3HT:PCBM:LCV blend thin film was measured 1.75 times as high as that of P3HT:PCBM blend thin film, as a result of LCV-induced trap filling in the bandgap of PCBM. The power conversion efficiency for the inverted device using the photoactive layer of P3HT:PCBM:LCV could be 1.22 times as high as that for the inverted device using the conventional photoactive layer of P3HT:PCBM, mostly because (1) the higher electron mobility could enhance the exciton dissociation and thereby short-circuit current density in the former relative to the latter; (2) the increase in the electron concentration of PCBM zone in P3HT:PCBM:LCV blend thin film may help blocking holes diffusion towards cathode, improving the hole collection efficiency and thereby fill factor of device. We provide a new insight on optimizing the electron-conducting property of bulk-heterojunction photoactive thin film, useful for pushing forward inverted OSCs towards the cost-effective commercialization. [ABSTRACT FROM AUTHOR]

Examines the role of nitric oxide in the activation of lymphokine-activated killer (LAK) cells among patients with bladder cancer in China. Cytotoxicity of LAK cells; Determination of the activity of nitric oxide synthase in LAK cells; Inhibition of sodium nitroprusside.