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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]

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 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]

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]

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]