P-type Organic Thin-film Transistors Research Articles

Comparison of electrical characteristics for p-type and n-type organic thin film transistors using copper phthalocyanine

The p-type and n-type organic thin film transistors (OTFTs) were fabricated in the same experimental conditions by using hexadecahydro copper phthalocyanine (H 16CuPc) and hexadecafluoro copper phthalocynine (F 16CuPc) molecules, respectively. The mobilities of H 16CuPc and F 16CuPc-based OTFT devices in saturation region were measured to be ∼1.22 × 10 −3 cm 2/V s and ∼1.04 × 10 −3 cm 2/V s, respectively. The temperature dependence of the mobility and activation energy ( E a) for both OTFTs were measured in saturation and linear regions of the drain-source current. We found that the E a of the F 16CuPc-based OTFTs was lower than that of H 16CuPc-based ones. The gate voltage ( V g) dependence of the field-effect mobility measured in linear region for the F 16CuPc-based OTFTs was more stable, i.e., weaker variation of the field-effect mobility with increasing V g, than that of the H 16CuPc-based ones. The high electron affinity of the hexadecafluorine (F 16) in CuPc contributed to the effective electron accumulation in the active channel.

Structure Property Relationships: Asymmetric Oligofluorene−Thiophene Molecules for Organic TFTs

Fluorene−thiophene oligomers show great promise as the active material in p-type organic thin film transistors (TFTs) because of their good performance and good stability under ambient conditions. In this study, a series of fluorene−thiophene co-oligomers were asymmetrically substituted with an alkyl group to probe the effect chemical structure has on their thin film properties. The alkyl groups are n-hexyl, n-octyl, and n-dodecyl, respectively. These oligomers were characterized by elemental analysis, mass spectrometry, differential scanning calorimetry, and thermogravimetric analysis, whereas the thin films of these oligomers were characterized by X-ray diffraction, atomic force microscopy, and field-effect transistor measurements. We found that the performance of these asymmetric molecules is similar to their symmetric counterparts. Mobilities as high as 0.16 cm2 V-1 s-1 were found for the n-dodecyl-substituted oligomer.

Low voltage complementary organic inverters

We have developed a method for integrating n- and p-type organic thin-film transistors (OTFTs) on the same substrate. An integrated shadow mask was used for the n- and p-type semiconductor patterning. The integrated shadow mask can be aligned with submicron accuracy relative to the OTFT substrate. This allows for the integration at transistor level of n- and p-type OTFTs on the same substrate. A complementary inverter was fabricated, showing excellent performance while operating at a supply voltage of 2V.

Influence of transistor parameters on the noise margin of organic digital circuits

The concept of noise margin is crucial in the design and operation of digital logic circuits. Analytical expressions for the transfer curves of an inverter based on two depletion-mode p-type organic thin-film transistors (OTFTs) were calculated. Based on these expressions, the values for the noise margin of organic-based inverters were calculated. In this paper, the influence of the OTFT parameters on the noise margin is presented. Knowing that statistical variations of the transistor parameters are inherent to OTFT technology, these statistical variations are also taken into account. Finally, a circuit yield analysis is presented.

Integrated shadow mask method for patterning small molecule organic semiconductors

We have developed a simple and efficient method for patterning small molecule semiconductors for applications in the field of organic electronics. In our approach, a profile is created using a single layer of photoresist, defining the regions where the organic semiconductor is to be deposited. Subsequent deposition of a small molecule semiconductor results in a discontinuity of the semiconductor film at the photoresist edge. The resulting transistor characteristics have an off current that is systematically below 1pA. We demonstrate both p-type and n-type organic thin-film transistors using this method, using pentacene and copper hexadecafluorophthalocyanine (F16CuPc), respectively.

Facile fabrication method for p∕n-type and ambipolar transport polyphenylenevinylene-based thin-film field-effect transistors by blending C60 fullerene

We have demonstrated the solution-processed p- and n-type transports including ambipolar transport organic thin-film transistors (OTFTs), required for complementary thin-film integrated circuit technology, by a facile method of blending the n-type C60 and the p-type [poly(2-methoxy-5-[2’-ethyl-hexyloxy]-1,4-phenylene vinylene] (MEH-PPV). The carrier transport of PPV-based thin-film field-effect transistors with various C60 compositions are investigated by using the field-effect gated structure. One of the important findings is that tunable electronic properties of OTFTs are achieved by controlling C60 composition using a simple and an inexpensive spin-cast technology. The mobility increases with increase in the C60 composition in both n- and p-type OTFTs. Temperature measurements on n-type OTFTs revealed that transport follows a thermally activated hopping transport model with small activation energy.