PERYLENE IMIDE/DIIMIDE BASED ORGANIC FIELD

EFFECT TRANSISTORS-OFETs AND A METHOD OF

PRODUCING THE SAME

[001] In organic electronics, much progress has been made in recent years in the development of FET based on organic semi conductors, OFETs. Related information can be found in Applied Physics Letters by Th. B. Singh et al. Appl. Phys. Lett. 85, 5409 (2004); Nanoelectronics and Information Technology : Advanced Elecronics Materials and Novel Devices, edited by R.Waser (2003) and C. D. Dimitrakopoulos and D. J. Mascaro, IBM J. Res. Dev., 45, 11 (2001); G. Horowitz, Adv. Funct. Mater., 13, 53 (2003).

[002] There has been a growing interest in researches on OFETs with high mobility (μ) utilizing the large field of material chemistry. (See. V. Podzorov, S. E. Sysoev, E. Loginova, V. M. Pudalov and M. E. Gershenson, Appl. Phys. Lett., 83, 3504 (2003)).

[003] OFET-Organic field-effect transistors among the general organic electronic devices are of great interest for switching devices, flexible displays, smart cards and in large area sensors. The advantage of these devices are the combination of solution processable and potentially lower cost fabrications such as printing over the existing device technology.

[004] OFET applications using low-cost production and large area coverage such as radio frequency IDs, smart tags, textile integrated electronics, etc.. are known. For reference, see J. A. Rogers, Z. bao, K. Baldwin, A. Dodabalapur, B. Crone, V. R. Raju, V. Kuck, H. Katz, K. Amundson, J. Ewing and P. Drzaic, Proc. Natl. Acad. Sci. USA, 98, 4835 (2001).

[005] Solution-processed large area printable OFETs have a great potential in future applications.

[006] In the present invention, ambipolar, solution processed n-channel organic field effect transistors (OFETs) having high mobilities based on perylene diimide, PDI, absorbing in visible region (< 530 nm) derivatives are disclosed.

[007] The synthesis, design and application of n-channel organic field effect transistors

(OFETs) based on N,N'-bis(dehydroabietyl)-3,4,9,10-perylene diimide (PDI) derivative has shown electron mobility, μ _« 7 x 10 ^' cm .V .s ^" and hole μ _« 8 x 10 ⁵ cm ² .V ^' '.s ^' '. Less soluble, air stable, n-channel based N-(cyclohe xyl)perylene-3,4,9,10-tetracarboxylic-3,4-anhydride-9,10-imi de showed a mobility of μ _« 10 ^'s cm ² .VV.

[008] PhotOFETs, functioning under solar irradiations, can also be constructed with

perylene imides/diimides.

[009] H. E. Katz reports the NDI based OFETs, constructed by vapor phase deposition.

[010] For reference see a) H. E. Katz, J. Johnson, A. J. Lovinger and W. Li, J. Am.

Chem. Soc, 122, 7787 (2000) b) H. E. Katz, W. Li, A. J. Lovinger, US Patent (2002),

(Agere Systems Guardian Corp., USA), USXXAM US 6387727 Bl 20020514. [011] The invention is described herebelow and in drawings attached hereto wherein :

[012] Figure 1 is a scheme of the staggered mode n-channel OFET device structure.

[013] Figure 2 shows the molecular structures employed in OFETs; a) BCB dielectric polymer, b) PVA (MOWIOL) dielectric polymer, c)

N,N'-bis-(dehydroabietyl)-3,4,9, 10- perylenebis [014] (dicarboximide) semiconductor, d) N-

(cyclohexyl)perylene-3, 4,9,10-tetracarboxy Hc- [015] 3,4-anhydride-9,10-imide semiconductor, e) N,N'-bis-(butyl)-l,4,5,8- naph- thalenebis

[016] (dicarboximide) semiconductor, f) Naphthalene dibenzimidazole semiconductor.

[017] Figure 3 is the transistor, output / vs. V , and transfer, / vs. V . characteristics of OFET with N,N'-bis-(butyl)-l,4,5,8-naphthalenebis (dicarboximide) as an active semiconducting layer. [018] Figure 4 shows the AFM images of N,N'-bis-(butyl)-l,4,5,8- naph- ¹ thalenebis(dicarboximide) thin film spin coated on top of PVA film. [019] Figure 5 shows output / vs. V , characteristics OFET curves of ambipolar OFET with N,N'-bis-(dehydroabietyl)-3,4,9,10-perylene bis (dicarboximide) as an active semiconducting layer. [020] Figure 6 shows transfer / ds vs. V gs characteristics of

N,N'-bis-(dehydroabietyl)-3,4,9,10-perylene bis (dicarboximide) FET showing electron enhancement current at positive gate voltage and hole enhancement current at negative gate voltage. [021] Figure 7 shows AFM image of ambipolar

N,N'-bis-(dehydroabietyl)-3,4,9, 10-perylene bis [022] (dicarboximide) on PVA coated film.

[023] Figure 8 shows transistor, I (V ), and transfer, I vs. V , characteristic OFET curves of N-

[024] (cyclohexyl)perylene-3,4,9,10-tetracarboxylic-3,4-anhydride- 9,10-imide.

[025] Solution processed n-channel organic field effect transistors (OFETs) based on

N,N'-bis(butyl)-l,4,5,8-naphthalene diimide, NDI, derivative, constructed as a reference to PDI-OFET; strong electron accepting ability and good solubility have been disclosed. NDI based OFETs showed mobilities up to 0.05 Cm ² V ¹ S ^"1 and operated both in inert conditions and air. Mobility of n-butyl NDI is higher than the reported

thin film alkyl derivative of NDI OFET 0.03 cmVV ⁶ . Naphthalene diimides absorb in UV range, < 380 nm. The crystalline structure of NDI in OFET device is proven by atomic force microscopy (AFM) pictures.

[026] A schematic view of the device is shown in Figure 1. The manufacturing process of the device starts with etching the electrically conductive indium tin oxide (ITO) on the glass substrate. After patterning the ITO and cleaning in the ultrasonic bath, PVA (poly- vinyl alcohol) dielectric layer with average molecular weight of 127.000 (Mowiol ^® 40-88) from Sigma-Aldrich® is spin-coated from water solution with a 10 % wt. ratio. A highly viscous PVA solution gives a transparent film by spin coating at 1500 rpm which results in 2 μm thick film forming the dielectric layer. Same experiment was conducted with divinyltetramethyldisiloxane-bis(benzocyclobutene) BCB as dielectric layer. BCB was used as received from Dow Chemicals and curing was done according to the standard procedure which is described in Lay-Lay Chua, Peter K. H. Ho, Henning Sirringhaus and R.H. Friend, Appl. Phys. Lett., 84, 3400 (2004).

[027] The top source and drain electrode, LiF/Al (0.6/60 nm) was evaporated under vacuum (2 x 10 ^" mbar) through a shadow mask. The channel length, L of the device is 35 μm with channel width, W = 1.4 mm which resulted in W/L ratio of « 40. From the measurement of dielectric thickness, d = 2 μm; _ε BCB = 2.6, dielectric capacitance C BCB =

1.2 nF/cm was estimated. All device transport and electrical characterisation was carried out both in air and under argon environment. Keithley® 236 and Keithley® 2400 Source-Measurements Units instruments were used for the steady state current- voltage measurements. Surface morphology and thickness of the dielectric was determined with a Digital Instrument® 3100 atomic force microscope (AFM) and a Dektak® surface profilometer.

[028] As shown in Figure 7, the semiconductor layer of dehydroabietyl perylene diimide has a very smooth surface with roughness of <5 nm, a spin coated layer at thickness of 150 nm. Perylene diimides and monoimides absorb in visible region <530 nm. In a recent study, it was proved that the first few monolayers next to the dielectric layer dominate the charge transport. See. F. Dinelli, M. Murgia, P. Levy , M. Cavallini, F. Biscarini, D. M. de Leeuw, Phys. Rev. Lett., 92, 116802 (2004).

[029] LiF /Al has been selected as drain and source electrode as it is expected to form ohmic contact on aromatic imides. See a) V. D. Mihailetchi, J. K. J. van Duren, P. W. M. Blom, J. C. Hummelen, R. A. J. Janssen, J. M. Kroon, M. T. Rispens, W. J. H. Verhees and M. M. Wienk, Adv. Func. Mater. 13, 43 (2003). b) G. J. Matt, N. S. Sariciftci and T. Fromherz, Appl. Phys. Lett. 84, 1570 (2004).

[030] Figures 3 and 5 show the typical transistor and transfer characteristics of a device with a well saturated curve occurring pinch off at drain source voltage V ds(sat) ³ V gs (gate

Voltage). For the same device (Figures 3 and 5) the transfer characteristics at different

V ds have been measured.

[031] As seen in figures 3 and 5, according to the equation (1): (S. M. Sze, Physics of

Semiconductor Devices (Wiley, New York, 1981) [032]

'.-* ^! £ 2L ^»(> -tf <» [033] N,N'-bis(dehydroabietyl)-3,4,9,10-perylene diimide (PDI) derivative has shown electron mobility of μ = 7 x 10 ^s cm ² .V ^"1 .s ^"1 and hole mobility 8 x 10 ⁵ cmlv'.s ^" '. Low solubility, air stable, n-channel based N-

(cyclohexyl)perylene-3,4,9,10-tetracarboxylic-3,4-anhydri de-9,10-imide showed electron mobility μ = 10 ^s crrΛvΛs ^"1 . N,N'-bis(butyl)-l,4,5,8-naphthalene diimide, NDI, derivative, constructed as a reference to PDI-OFET; strong electron accepting ability and good solubility have been featured. NDI based OFETs showed electron mobilities μ up to 0.05 cm .V'.s ^"1 and operated in both inert conditions and air. Mobility of n-butyl NDI is higher than the reported thin film NDI OFET 0.03 cm ² .V ^" '.s ^" '. (For reference see H. E. Katz, J. Johnson, A. J. Lovinger and W. Li, J. Am. Chem. Soc, 122, 7787 (2000) It is known that naphthalene imides and perylene imides have identical physical, chemical characteristics as naphthalene diimides and perylene diimides. Therefore, similar observations in OFETs would be detected with naphthalene monoimides, as seen in perylene monoimide and in perylene diimide at our applications.