Continuously Variable Hole Injection in Organic Light Emitting Diodes

Enhancement of polymer electronics via surface states on highly doped polymeric anodes

“…The data indicate that while there is very little variation in V oc between the four devices (only about 50 mV), there does appear to be a correlation between the measured short-circuit current (I sc ) and E eq . These results are in contradiction with earlier work [6,7], which demonstrated that the work function, φ W , of the PEDOT processed under inert gas atmosphere and measured by a Kelvin probe depends linearly on the (initial) E eq of the doped PEDOT layer with a slope of 0.8 [6,7]. Similarly, from PV measurements on a series of solar cells, PEDOT(E eq )/MDMO-PPV : PCBM/Al, prepared in inert atmospheres the V oc was also found to be linearly dependent upon E eq with the identical slope of 0.8 [7].…”

“…We reported earlier [6,7] that irreproducible results are obtained whenever the φ W of PEDOT exceeds the oxidation potential of MDMO-PPV (shaded area in figure 3(b)), preventing the use of polymeric anodes with the highest conductivities. Such observations were not made after the PEDOT was exposed to air, which can be attributed to the fact that the interfacial layer provides a doping level below the oxidation potential of MDMO-PPV in accordance with our Kelvin probe measurements.…”

“…Thus, the direct correlation between the CPD and the PV measurements is confirmed by the results presented here. For comparison, we present the CPD and V oc data obtained here together with earlier data from [6] in figure 3.…”

Enhancement of polymer electronics via surface states on highly doped polymeric anodes

“…The data indicate that while there is very little variation in V oc between the four devices (only about 50 mV), there does appear to be a correlation between the measured short-circuit current (I sc ) and E eq . These results are in contradiction with earlier work [6,7], which demonstrated that the work function, φ W , of the PEDOT processed under inert gas atmosphere and measured by a Kelvin probe depends linearly on the (initial) E eq of the doped PEDOT layer with a slope of 0.8 [6,7]. Similarly, from PV measurements on a series of solar cells, PEDOT(E eq )/MDMO-PPV : PCBM/Al, prepared in inert atmospheres the V oc was also found to be linearly dependent upon E eq with the identical slope of 0.8 [7].…”

“…We reported earlier [6,7] that irreproducible results are obtained whenever the φ W of PEDOT exceeds the oxidation potential of MDMO-PPV (shaded area in figure 3(b)), preventing the use of polymeric anodes with the highest conductivities. Such observations were not made after the PEDOT was exposed to air, which can be attributed to the fact that the interfacial layer provides a doping level below the oxidation potential of MDMO-PPV in accordance with our Kelvin probe measurements.…”

“…Thus, the direct correlation between the CPD and the PV measurements is confirmed by the results presented here. For comparison, we present the CPD and V oc data obtained here together with earlier data from [6] in figure 3.…”

Electropolymerized Conjugated Polyelectrolytes with Tunable Work Function and Hydrophobicity as an Anode Buffer in Organic Optoelectronics

“…Earlier reports found a high influence of the doping voltage on the work function of conducting polymers. − When doping the copolymer films at voltages between 0.4 and 0.8 V in water, we could not observe any difference in the work function because the oxidation level is mainly determined by the EDOT–SuNa ratio. After doping these films in 0.1 M LiClO 4 solution at different voltages, we measured a small increase in work function of approximately 0.1 eV between the films doped at 0.4 and 0.8 V. This increase is low, and we expect that such a procedure is not suitable for obtaining stably high work function values because of overoxidation effects and the instability of highly oxidized films under ambient conditions.…”

Investigating Work Function Tunable Hole-Injection/Transport Layers of Electrodeposited Polycarbazole Network Thin Films

“…Also, solubility is a problem with a growing polycarbazole linear chain. In the case of the PVK, the polymer backbone helps the electrodeposition due to the improved adhesion strength onto the surface . Also the carbazole monomer tethered to the polymer backbone lowers the activation energy of cross-linking of the electroactive unit.…”

Enhancement of polymer electronics via surface states on highly doped polymeric anodes

“…The data indicate that while there is very little variation in V oc between the four devices (only about 50 mV), there does appear to be a correlation between the measured short-circuit current (I sc ) and E eq . These results are in contradiction with earlier work [6,7], which demonstrated that the work function, φ W , of the PEDOT processed under inert gas atmosphere and measured by a Kelvin probe depends linearly on the (initial) E eq of the doped PEDOT layer with a slope of 0.8 [6,7]. Similarly, from PV measurements on a series of solar cells, PEDOT(E eq )/MDMO-PPV : PCBM/Al, prepared in inert atmospheres the V oc was also found to be linearly dependent upon E eq with the identical slope of 0.8 [7].…”

“…We reported earlier [6,7] that irreproducible results are obtained whenever the φ W of PEDOT exceeds the oxidation potential of MDMO-PPV (shaded area in figure 3(b)), preventing the use of polymeric anodes with the highest conductivities. Such observations were not made after the PEDOT was exposed to air, which can be attributed to the fact that the interfacial layer provides a doping level below the oxidation potential of MDMO-PPV in accordance with our Kelvin probe measurements.…”

“…Thus, the direct correlation between the CPD and the PV measurements is confirmed by the results presented here. For comparison, we present the CPD and V oc data obtained here together with earlier data from [6] in figure 3.…”

Electropolymerized Conjugated Polyelectrolytes with Tunable Work Function and Hydrophobicity as an Anode Buffer in Organic Optoelectronics

“…Earlier reports found a high influence of the doping voltage on the work function of conducting polymers. − When doping the copolymer films at voltages between 0.4 and 0.8 V in water, we could not observe any difference in the work function because the oxidation level is mainly determined by the EDOT–SuNa ratio. After doping these films in 0.1 M LiClO 4 solution at different voltages, we measured a small increase in work function of approximately 0.1 eV between the films doped at 0.4 and 0.8 V. This increase is low, and we expect that such a procedure is not suitable for obtaining stably high work function values because of overoxidation effects and the instability of highly oxidized films under ambient conditions.…”

Investigating Work Function Tunable Hole-Injection/Transport Layers of Electrodeposited Polycarbazole Network Thin Films

“…Also, solubility is a problem with a growing polycarbazole linear chain. In the case of the PVK, the polymer backbone helps the electrodeposition due to the improved adhesion strength onto the surface . Also the carbazole monomer tethered to the polymer backbone lowers the activation energy of cross-linking of the electroactive unit.…”

Enhancement of polymer electronics via surface states on highly doped polymeric anodes

“…The data indicate that while there is very little variation in V oc between the four devices (only about 50 mV), there does appear to be a correlation between the measured short-circuit current (I sc ) and E eq . These results are in contradiction with earlier work [6,7], which demonstrated that the work function, φ W , of the PEDOT processed under inert gas atmosphere and measured by a Kelvin probe depends linearly on the (initial) E eq of the doped PEDOT layer with a slope of 0.8 [6,7]. Similarly, from PV measurements on a series of solar cells, PEDOT(E eq )/MDMO-PPV : PCBM/Al, prepared in inert atmospheres the V oc was also found to be linearly dependent upon E eq with the identical slope of 0.8 [7].…”

“…We reported earlier [6,7] that irreproducible results are obtained whenever the φ W of PEDOT exceeds the oxidation potential of MDMO-PPV (shaded area in figure 3(b)), preventing the use of polymeric anodes with the highest conductivities. Such observations were not made after the PEDOT was exposed to air, which can be attributed to the fact that the interfacial layer provides a doping level below the oxidation potential of MDMO-PPV in accordance with our Kelvin probe measurements.…”

“…Thus, the direct correlation between the CPD and the PV measurements is confirmed by the results presented here. For comparison, we present the CPD and V oc data obtained here together with earlier data from [6] in figure 3.…”

Electropolymerized Conjugated Polyelectrolytes with Tunable Work Function and Hydrophobicity as an Anode Buffer in Organic Optoelectronics

“…Earlier reports found a high influence of the doping voltage on the work function of conducting polymers. − When doping the copolymer films at voltages between 0.4 and 0.8 V in water, we could not observe any difference in the work function because the oxidation level is mainly determined by the EDOT–SuNa ratio. After doping these films in 0.1 M LiClO 4 solution at different voltages, we measured a small increase in work function of approximately 0.1 eV between the films doped at 0.4 and 0.8 V. This increase is low, and we expect that such a procedure is not suitable for obtaining stably high work function values because of overoxidation effects and the instability of highly oxidized films under ambient conditions.…”

Investigating Work Function Tunable Hole-Injection/Transport Layers of Electrodeposited Polycarbazole Network Thin Films

“…Also, solubility is a problem with a growing polycarbazole linear chain. In the case of the PVK, the polymer backbone helps the electrodeposition due to the improved adhesion strength onto the surface . Also the carbazole monomer tethered to the polymer backbone lowers the activation energy of cross-linking of the electroactive unit.…”