Limits...
High-Performance Flexible Bottom-Gate Organic Field-Effect Transistors with Gravure Printed Thin Organic Dielectric.

Vaklev NL, Müller R, Muir BV, James DT, Pretot R, van der Schaaf P, Genoe J, Kim JS, Steinke JH, Campbell AJ - Adv Mater Interfaces (2014)

View Article: PubMed Central - PubMed

Affiliation: Experimental Solid State Group and the Centre for Plastic Electronics, Department of Physics, Blackett Laboratory, South Kensington Campus, Imperial College London London, SW7 2AZ, UK E-mail: alasdair.campbell@imperial.ac.uk.

AUTOMATICALLY GENERATED EXCERPT
Please rate it.

One of the key advantages of organic field-effect transistors (OFETs) is their ability to form flexible, conformable and lightweight electronic devices, e.g. radio frequency identification (RFID) tags, microprocessors and flexible displays... While high performance source, drain and gate electrodes and interconnects require metal evaporation under vacuum, ideally the dielectric and organic semiconductor (OSC) should be processed from solution under ambient conditions to reduce fabrication costs... These can be processed by techniques such as spin-casting, gravure printing and ink-jet printing at room temperature in ambient conditions... To avoid significant gate leakage current these polymer dielectrics have typically been deposited with film thicknesses ≥ 500 nm, resulting in high OFET operating voltages ≥20 V... To fabricate the BG BC OFETs, non-birefringent plastic substrates coated with a transparent conducting oxide (TCO) were used as required for flexible display applications... Breakdown voltages of the spin-cast and printed films were typically >2.4 MV cm (Figure S4)... Therefore, we conclude that gravure printing can produce dielectric films with comparable surface properties and homogeneity as spin-casting... Semiconductor crystallinity and charge-carrier mobility in BG BC OFETs is known to be affected by the dielectric surface energy, increasing with increasing water contact angle... The water contact angle of the dielectric surface with and without PαMS was found to be 90 ± 2° and 69 ± 2°, respectively... The SSV can be associated with the ratio between mobile and trapped charge-carriers at the semiconductor–dielectric interface as carriers first enter the channel when the OFET is switched from off- to on-state... The presence of PαMS therefore reduces the density of interfacial traps responsible for the SSV in TIPS-pentacene... Therefore, the triacrylate based dielectric can be processed using large-area compatible coating techniques such as gravure to give equally high performance devices as when it is spin-cast... In conclusion, we have demonstrated that it is possible to fabricate state-of-the-art flexible small molecule BG BC OFETs on plastic foil using a large-area scalable platform... Evaporated pentacene OFETs achieved an average mobility of 0.6 cm V s, which is state-of-the-art for this device geometry for flexible transistors on plastic... We also demonstrated that zone-casting can be used to fabricate small molecule OFETs on plastic with a polymer dielectric, TIPS-pentacene achieving an average mobility of 0.3 cm V s, which is state-of-the-art for this device geometry for flexible devices.

No MeSH data available.


(a–c) Transfer characteristics in saturation (Vds = −10 V) and linear (Vds = −2 V) regimes for OFETs with gravure printed dielectric and (a) evaporated pentacene, (b) zone-cast TIPS-pentacene and (c) spin-cast TIPS-pentacene. The source-drain current, Ids, is normalised to channel width and length, W and L, respectively. (d–f) AFM micrographs of the corresponding OSC crystals in the OFET channel for (a–c) respectively; (g–i) cross-polarised optical micrographs of transistor channels for (a–c) respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4493673&req=5

fig03: (a–c) Transfer characteristics in saturation (Vds = −10 V) and linear (Vds = −2 V) regimes for OFETs with gravure printed dielectric and (a) evaporated pentacene, (b) zone-cast TIPS-pentacene and (c) spin-cast TIPS-pentacene. The source-drain current, Ids, is normalised to channel width and length, W and L, respectively. (d–f) AFM micrographs of the corresponding OSC crystals in the OFET channel for (a–c) respectively; (g–i) cross-polarised optical micrographs of transistor channels for (a–c) respectively.

Mentions: For pentacene OFETs, the OSC was deposited by vacuum-sublimation and gave state-of-the-art performance. The transfer characteristics for OFETs (Figure3a) showed no hysteresis and an AFM micrograph of the channel region reveals large crystalline domains (Figure 3b). The layer of PαMS (6 nm thick) acts as a non-covalent surface modification of the dielectric with pentacene[7,20] improving interfacial OSC packing and morphology. Semiconductor crystallinity and charge-carrier mobility in BG BC OFETs is known to be affected by the dielectric surface energy, increasing with increasing water contact angle.[21] The water contact angle of the dielectric surface with and without PαMS was found to be 90 ± 2° and 69 ± 2°, respectively. Pentacene OFETs with PαMS achieved an average saturation mobility of 0.6 ± 0.1 cm2 V−1 s−1 and an onset voltage of about 1 V. This mobility is the highest yet reported for this semiconductor on flexible substrates with the BG configuration, exceeding the previously reported value of 0.3 cm2 V−1 s−1 using an inorganic dielectric[22] (Figure 2c). Compared to the bare dielectric, PαMS increased the saturation mobility ten-fold, indicating improved crystal growth and orientation on the less polar surface. Without PαMS, the devices have a higher average turn-on voltage of about 5 V (Figure S5c), indicating more localised traps at the interface from grain boundaries and crystal defects.[23] AFM data supported this theory, showing that the grain size of pentacene deposited on the bare dielectric was about five-fold smaller (Figure S8) than pentacene on the PαMS surface (Figure S9a, b).


High-Performance Flexible Bottom-Gate Organic Field-Effect Transistors with Gravure Printed Thin Organic Dielectric.

Vaklev NL, Müller R, Muir BV, James DT, Pretot R, van der Schaaf P, Genoe J, Kim JS, Steinke JH, Campbell AJ - Adv Mater Interfaces (2014)

(a–c) Transfer characteristics in saturation (Vds = −10 V) and linear (Vds = −2 V) regimes for OFETs with gravure printed dielectric and (a) evaporated pentacene, (b) zone-cast TIPS-pentacene and (c) spin-cast TIPS-pentacene. The source-drain current, Ids, is normalised to channel width and length, W and L, respectively. (d–f) AFM micrographs of the corresponding OSC crystals in the OFET channel for (a–c) respectively; (g–i) cross-polarised optical micrographs of transistor channels for (a–c) respectively.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493673&req=5

fig03: (a–c) Transfer characteristics in saturation (Vds = −10 V) and linear (Vds = −2 V) regimes for OFETs with gravure printed dielectric and (a) evaporated pentacene, (b) zone-cast TIPS-pentacene and (c) spin-cast TIPS-pentacene. The source-drain current, Ids, is normalised to channel width and length, W and L, respectively. (d–f) AFM micrographs of the corresponding OSC crystals in the OFET channel for (a–c) respectively; (g–i) cross-polarised optical micrographs of transistor channels for (a–c) respectively.
Mentions: For pentacene OFETs, the OSC was deposited by vacuum-sublimation and gave state-of-the-art performance. The transfer characteristics for OFETs (Figure3a) showed no hysteresis and an AFM micrograph of the channel region reveals large crystalline domains (Figure 3b). The layer of PαMS (6 nm thick) acts as a non-covalent surface modification of the dielectric with pentacene[7,20] improving interfacial OSC packing and morphology. Semiconductor crystallinity and charge-carrier mobility in BG BC OFETs is known to be affected by the dielectric surface energy, increasing with increasing water contact angle.[21] The water contact angle of the dielectric surface with and without PαMS was found to be 90 ± 2° and 69 ± 2°, respectively. Pentacene OFETs with PαMS achieved an average saturation mobility of 0.6 ± 0.1 cm2 V−1 s−1 and an onset voltage of about 1 V. This mobility is the highest yet reported for this semiconductor on flexible substrates with the BG configuration, exceeding the previously reported value of 0.3 cm2 V−1 s−1 using an inorganic dielectric[22] (Figure 2c). Compared to the bare dielectric, PαMS increased the saturation mobility ten-fold, indicating improved crystal growth and orientation on the less polar surface. Without PαMS, the devices have a higher average turn-on voltage of about 5 V (Figure S5c), indicating more localised traps at the interface from grain boundaries and crystal defects.[23] AFM data supported this theory, showing that the grain size of pentacene deposited on the bare dielectric was about five-fold smaller (Figure S8) than pentacene on the PαMS surface (Figure S9a, b).

View Article: PubMed Central - PubMed

Affiliation: Experimental Solid State Group and the Centre for Plastic Electronics, Department of Physics, Blackett Laboratory, South Kensington Campus, Imperial College London London, SW7 2AZ, UK E-mail: alasdair.campbell@imperial.ac.uk.

AUTOMATICALLY GENERATED EXCERPT
Please rate it.

One of the key advantages of organic field-effect transistors (OFETs) is their ability to form flexible, conformable and lightweight electronic devices, e.g. radio frequency identification (RFID) tags, microprocessors and flexible displays... While high performance source, drain and gate electrodes and interconnects require metal evaporation under vacuum, ideally the dielectric and organic semiconductor (OSC) should be processed from solution under ambient conditions to reduce fabrication costs... These can be processed by techniques such as spin-casting, gravure printing and ink-jet printing at room temperature in ambient conditions... To avoid significant gate leakage current these polymer dielectrics have typically been deposited with film thicknesses ≥ 500 nm, resulting in high OFET operating voltages ≥20 V... To fabricate the BG BC OFETs, non-birefringent plastic substrates coated with a transparent conducting oxide (TCO) were used as required for flexible display applications... Breakdown voltages of the spin-cast and printed films were typically >2.4 MV cm (Figure S4)... Therefore, we conclude that gravure printing can produce dielectric films with comparable surface properties and homogeneity as spin-casting... Semiconductor crystallinity and charge-carrier mobility in BG BC OFETs is known to be affected by the dielectric surface energy, increasing with increasing water contact angle... The water contact angle of the dielectric surface with and without PαMS was found to be 90 ± 2° and 69 ± 2°, respectively... The SSV can be associated with the ratio between mobile and trapped charge-carriers at the semiconductor–dielectric interface as carriers first enter the channel when the OFET is switched from off- to on-state... The presence of PαMS therefore reduces the density of interfacial traps responsible for the SSV in TIPS-pentacene... Therefore, the triacrylate based dielectric can be processed using large-area compatible coating techniques such as gravure to give equally high performance devices as when it is spin-cast... In conclusion, we have demonstrated that it is possible to fabricate state-of-the-art flexible small molecule BG BC OFETs on plastic foil using a large-area scalable platform... Evaporated pentacene OFETs achieved an average mobility of 0.6 cm V s, which is state-of-the-art for this device geometry for flexible transistors on plastic... We also demonstrated that zone-casting can be used to fabricate small molecule OFETs on plastic with a polymer dielectric, TIPS-pentacene achieving an average mobility of 0.3 cm V s, which is state-of-the-art for this device geometry for flexible devices.

No MeSH data available.