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High-efficiency, solution-processed, multilayer phosphorescent organic light-emitting diodes with a copper thiocyanate hole-injection/hole-transport layer.

Perumal A, Faber H, Yaacobi-Gross N, Pattanasattayavong P, Burgess C, Jha S, McLachlan MA, Stavrinou PN, Anthopoulos TD, Bradley DD - Adv. Mater. Weinheim (2014)

Bottom Line: Copper thiocyanate (CuSCN) is introduced as a hole-injection/hole-transport layer (HIL/HTL) for solution-processed organic light-emitting diodes (OLEDs).The OLED devices reported here with CuSCN as HIL/HTL perform significantly better than equivalent devices fabricated with a PEDOT:PSS HIL/HTL, and solution-processed, phosphorescent, small-molecule, green OLEDs with maximum luminance ≥10 000 cd m(-2) , maximum luminous efficiency ≤50 cd A(-1) , and maximum luminous power efficiency ≤55 lm W(-1) are demonstrated.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics and Centre for Plastic Electronics, Blackett Laboratory, Imperial College London, London, SW7 2AZ, UK.

No MeSH data available.


TEM image of the focused ion beam (FIB)-milled cross section of a complete CuSCN HIL/HTL OLED device (right side), together with a schematic of its stack structure (left side). The EML and ETL layers remain unresolved but the interface between HIL/HTL and EML is observed to be sharp and continuous, as indeed is the higher lying interface between ETL and Ca.
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fig02: TEM image of the focused ion beam (FIB)-milled cross section of a complete CuSCN HIL/HTL OLED device (right side), together with a schematic of its stack structure (left side). The EML and ETL layers remain unresolved but the interface between HIL/HTL and EML is observed to be sharp and continuous, as indeed is the higher lying interface between ETL and Ca.

Mentions: In the fabrication of multilayer OLEDs from solution, it is important that the solvent for each successive layer wets but does not dissolve/swell the previously deposited film(s); such solvents are described as orthogonal. Here, we spin coat an HIL/HTL on top of the insoluble ITO anode, spin coat the EML, and finally evaporate the ETL and Ca/Al cathode on top (cf. Experimental Section). The EML is dissolved in chlorobenzene (CB), which is known to be orthogonal to the standard water-soluble PEDOT:PSS HIL/HTL, thereby allowing straightforward device fabrication.[23] The CuSCN HIL/HTL is dissolved in diethyl sulfide (DES) and we have investigated the film formation of successive layers in CuSCN-based devices via cross-section transmission electron microscopy (TEM). Figure2 shows a cross-section TEM image of the complete device, with many of the individual layers in the stack clearly resolved and identified. The EML and ETL are not resolved as there is insufficient scattering contrast between them due to their very similar chemical composition. The CuSCN HIL/HTL fills the indentations in the ITO anode and is in turn uniformly coated by the EML. The CuSCN/EML interface is sharp and continuous with no apparent gaps or voids, demonstrating that CB is orthogonal to the DES spin-coated CuSCN film. The combined EML and ETL organic layers further planarize the device structure and yield a very flat surface onto which the Ca and Al are deposited. This is consistent with AFM measurements on EML films spin coated on both quartz and CuSCN-coated quartz substrates that show a very smooth and homogeneous surface topography with a root mean square (RMS) roughness ≤ 0.5 nm (Figures S1 and S2, Supporting Information). The TEM thickness values are consistent with the thicknesses measured by surface profilometry for individual layers deposited under the same conditions on glass substrates.


High-efficiency, solution-processed, multilayer phosphorescent organic light-emitting diodes with a copper thiocyanate hole-injection/hole-transport layer.

Perumal A, Faber H, Yaacobi-Gross N, Pattanasattayavong P, Burgess C, Jha S, McLachlan MA, Stavrinou PN, Anthopoulos TD, Bradley DD - Adv. Mater. Weinheim (2014)

TEM image of the focused ion beam (FIB)-milled cross section of a complete CuSCN HIL/HTL OLED device (right side), together with a schematic of its stack structure (left side). The EML and ETL layers remain unresolved but the interface between HIL/HTL and EML is observed to be sharp and continuous, as indeed is the higher lying interface between ETL and Ca.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4315901&req=5

fig02: TEM image of the focused ion beam (FIB)-milled cross section of a complete CuSCN HIL/HTL OLED device (right side), together with a schematic of its stack structure (left side). The EML and ETL layers remain unresolved but the interface between HIL/HTL and EML is observed to be sharp and continuous, as indeed is the higher lying interface between ETL and Ca.
Mentions: In the fabrication of multilayer OLEDs from solution, it is important that the solvent for each successive layer wets but does not dissolve/swell the previously deposited film(s); such solvents are described as orthogonal. Here, we spin coat an HIL/HTL on top of the insoluble ITO anode, spin coat the EML, and finally evaporate the ETL and Ca/Al cathode on top (cf. Experimental Section). The EML is dissolved in chlorobenzene (CB), which is known to be orthogonal to the standard water-soluble PEDOT:PSS HIL/HTL, thereby allowing straightforward device fabrication.[23] The CuSCN HIL/HTL is dissolved in diethyl sulfide (DES) and we have investigated the film formation of successive layers in CuSCN-based devices via cross-section transmission electron microscopy (TEM). Figure2 shows a cross-section TEM image of the complete device, with many of the individual layers in the stack clearly resolved and identified. The EML and ETL are not resolved as there is insufficient scattering contrast between them due to their very similar chemical composition. The CuSCN HIL/HTL fills the indentations in the ITO anode and is in turn uniformly coated by the EML. The CuSCN/EML interface is sharp and continuous with no apparent gaps or voids, demonstrating that CB is orthogonal to the DES spin-coated CuSCN film. The combined EML and ETL organic layers further planarize the device structure and yield a very flat surface onto which the Ca and Al are deposited. This is consistent with AFM measurements on EML films spin coated on both quartz and CuSCN-coated quartz substrates that show a very smooth and homogeneous surface topography with a root mean square (RMS) roughness ≤ 0.5 nm (Figures S1 and S2, Supporting Information). The TEM thickness values are consistent with the thicknesses measured by surface profilometry for individual layers deposited under the same conditions on glass substrates.

Bottom Line: Copper thiocyanate (CuSCN) is introduced as a hole-injection/hole-transport layer (HIL/HTL) for solution-processed organic light-emitting diodes (OLEDs).The OLED devices reported here with CuSCN as HIL/HTL perform significantly better than equivalent devices fabricated with a PEDOT:PSS HIL/HTL, and solution-processed, phosphorescent, small-molecule, green OLEDs with maximum luminance ≥10 000 cd m(-2) , maximum luminous efficiency ≤50 cd A(-1) , and maximum luminous power efficiency ≤55 lm W(-1) are demonstrated.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics and Centre for Plastic Electronics, Blackett Laboratory, Imperial College London, London, SW7 2AZ, UK.

No MeSH data available.