Modification of carbon nanotube transparent conducting films for electrodes in organic light-emitting diodes

Abstract

Single-walled carbon nanotube (SWCNT) transparent conducting films (TCFs) were fabricated for the electrodes of organic light-emitting diodes (OLEDs); three types of film were studied. The as-prepared SWCNT TCFs displayed a relatively low sheet resistance of 82.6 Ω/sq at 80.7 T% with a relatively large surface roughness of 30 nm. The TCFs were top-coated with poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) to obtain PEDOT:PSS-coated TCFs. The PEDOT:PSS cover improved the conductivity and decreased the surface roughness to 12 nm at the cost of film transmittance. The SWCNT TCFs mixed with PEDOT:PSS (PM-TCFs) exhibited a high conductivity (70.6 Ω/sq at 81 T%) and a low surface roughness (3 nm) and were thus selected as the best TCFs for OLEDs. Blue flexible OLEDs with 4,4'-bis(2,2'-diphenylvinyl)-1,1'-biphenyl (Dpvbi) as the emitting layer were fabricated on TCFs with the same structures to evaluate the performances of the different types of SWCNT films for use in OLEDs. Of these three types of OLEDs, the PM-TCF devices exhibited the optimal performance with a maximum luminance of 2587 cd m(-2) and a current efficiency of 5.44 cd A(-1). This result was explored using field-emission scanning electron microscopy and atomic force microscopy to further study the mechanisms that are involved in applying SWCNT TCFs to OLEDs.

Temperature and voltage dependent current–voltage behavior of single-walled carbon nanotube transparent conducting films

“…1b. The performance of the TCFs is good enough for touch screens, and the films with similar sheet resistance by spray coating can also be used as electrodes for OLEDs as described in our previous work [11].…”

“…It may need an open voltage around 4 V to overcome the energy barrier for good conductivity. This may influence the device performance under low voltage, for example, higher turnon voltage in OLEDs using CNT TCFs as electrodes [11,30]. Hence, it should pay more attention when design device using CNT films as electrodes under low voltage at room temperature.…”

“…TCFs fabricated using single-walled CNTs (SWCNTs) are widely explored in numerous applications such as electron field emitters [7], supercapacitors [8], thin-film transistors [9], organic photovoltaics [10], and organic light emitting diodes (OLEDs) [11,12]. TCFs have been fabricated using CNTs by various methods, such as vacuum filtration [13,14], spin coating [15], spray coating [16,17], dip coating [18], inkjet printing [19,20], gel coating [21], Mayer rod coating [22,23] and self-assembly methods [24].…”

Enhancement of Carrier Injection in OLEDs Utilizing Field Concentration to Carbon Nanotubes

“…In particular, CNT TCFs can be use as contact electrodes of flexible OLEDs. Recently, some group reported flexible OLEDs with CNT contact electrodes [1][2][3][4]. However, the devices have not shown better characteristics than those with conventional ITO electrodes.…”

Electrical and optical numerical modeling of DP-PPV based polymer light emitting diode

“…Furthermore, many advanced materials were explored in the manufacturing and studying OLEDs on the nanoscale like the quantum dots [20], carbon nanotubes [21] and nanowires [22].…”