Over the past decade, amorphous metal oxide semiconductors have attracted great interest as low-cost alternatives to thin film transistors (TFTs) due to their high electron mobility, high optical transparency, good environmental/thermal stability, and processing versatility. In contrast, realization of high performance transparent p-type oxide semiconductors remain intangible with urgent industrial demands. In this work, we report solution-processed inorganic p-type copper iodide (CuI) and oxide thin film transistors (TFTs). The spin coated CuI film showed high mobility over 2 cm2 V-1 s-1 by proper treatments such as optimization process condition and applying dopant. Transparent complementary inverters composed of p-type CuI and n-type indium gallium zinc oxide TFTs are demonstrated. We also introduce our recent results of perovskite transistors.
For at least the past 10 years, printed electronics has promised to revolutionize our daily life by making cost-effective electronic circuits and sensors available through mass production techniques, for their ubiquitous applications in wearable components, rollable and conformable devices, and point-of-care applications. In this presentation, I will give a talk on the recent progressive of my group on development of printed organic integrated circuits. I will mainly talk about on development of high performance inkjet printed unipolar and ambipolar polymer field-effect transistors (FETs), and applications to elementary organic complementary logic circuits by applying novel polymer dielectrics, new organic semiconducting and design new printing processes. In particular, we engineered and introduce new concept based for solution processed solid-state electrolyte gate insulators (SEGIs) by precise blending of P(VDF-TrFE) solution and P(VDF-HFP)-[EMIM][TFSI] gel solution resulting, after deposition of a thin film solid gate dielectric FETs, in ultrahigh field-effect mobility (μFET) and stable devices operating at low-voltage for several classes of unconventional semiconductors including -conjugated polymers, metal-oxides and other carbonaceous materials. By adding a minute amount (3% volume ratio for the optimal composition) of P(VDF-HFP)-[EMIM][TFSI] to the bulk fluorinated P(VDF-TrFE), high areal capacitance of > 4 µFcm-2 is reached thanks to the combined polarization of the -C-F interface dipoles and electrical double layers formation. To eliminate the integral complexity in differentiating field induced charge carriers from any possible carriers resulting from electrochemical doping of the semiconducting layer, we systematically measured the specific capacitance for each semiconductor/dielectric FET combination to avoid overestimation of the μFET extraction in our SEGI devices - a major common issue in several publications. For instance, with our engineered SEGIs, unprecedented hole mobility increase from ~10-2 to 5 cm2V-1s-1 (corresponding ~37 cm2V-1s-1 by commonly used method) at ≤ 2 V operation is reached in commercially available poly(3-hexylthiophene-2,5-diyl) (P3HT) FETs, and μFET exceeding 10 cm2V-1s-1 in others semiconductors.
Highly photosensitive organic phototransistors (OPTs) with an organic thin film transistors configuration based on a biphenyl end capped fused bithiophene oligomer (BPTT) and copper phthalocyanine (CuPC) were prepared. The measured maximum responsivity and the ratio of photocurrent to dark current (IPh/IDark) in BPTT and CuPC OPTs were 82 A/W, 2 A/W and 2.0 × 10<sup>5</sup>, 1000 under 365 nm UV light with 1.55 mW/cm<sup>2</sup>, respectively. The prepared OPTs showed a photocurrent response similar to the photo to current conversion efficiency (IPCE) spectrum of BPTT and CuPC. The main mechanisms responsible for photocurrent amplification in the devices were examined by comparing theoretical and measured data. The photovoltaic (turn-on) and photoconductive effect (turn-off) of the OPTs were determined by fitting to theoretical equations. The findings confirmed that the operation of the OPTs followed as photo-voltaic (turn-on state) and photo-conductive (turn-off state) behaviors.