Darmawati Darwis

Novel low voltage and solution processable organic thin film transistors based on water dispersed polymer semiconductor nanoparticulates

Two novel organic thin film transistor structures that combine a hygroscopic insulator with the use of water-dispersed polymer nanoparticles as the active layer are presented. In the first device structure, the semiconducting layer was fabricated from a nanoparticulate suspension of poly-(3-hexylthiophene) prepared through a mini-emulsion process using sodium dodecyl sulfate as the surfactant whereas a surfactant-free precipitation method has been used for the second device structure. In both cases, fully solution processable transistors have been fabricated in a top gate configuration with hygroscopic poly(4-vinylphenol) as the dielectric layer. Both device structures operate at low voltages (0 to -4V) but exhibit contrasting output characteristics. A systematic study is presented on the effect of surfactant on the synthesis of semiconducting nanoparticles, the formation of thin nanoparticulate films and, consequently, on device performance.

High‐Performance Thin Film Transistor from Solution‐Processed P3HT Polymer Semiconductor Nanoparticles

Nanoparticulate suspensions of semiconducting polymer poly‐3‐hexylthiophene (P3HT) have been prepared in water through a mini‐emulsion process using sodium dodecyl sulphate (SDS) as the surfactant. Using these suspensions, we have fabricated organic thin film transistors (OTFTs) in a top gate configuration. These devices operate at a low voltage and show output characteristics similar to those achieved when the P3HT film is spun from chloroform. To characterize the properties of the film made from the nanoparticle suspension, differential thermal analysis (TGA), differential scanning calorimetry (DSC), atomic force microscopy (AFM), fluorescence spectra analysis, ultraviolet/visible (UV/VIS) spectrophotometry and X‐ray photoelectron spectroscopy (XPS) have been used.

Surfactant Free P3HT / PCBM Nanoparticles for Organic Photovoltaics (OPV)

Initial attempts to prepare conducting polymer nanoparticles with ethanol as a solvent are described. Using poly (3‐hexylthiophene) (P3HT)/1‐(methoxycarbonylpropyl)‐1‐phenyl‐[6,6]C61 (PCBM) blends we demonstrate surfactant‐free synthesis and characterization of polymer nanoparticles in ethanol dispersion. The spectral features of the nanoparticles were investigated by UV‐vis spectrophotometry show that P3HT has an absorption maximum at ∼520 nm, while the absorption peak of PCBM lies at ∼330 nm. Corresponding fluorescence spectra of the nanoparticles show an emission peak at 630 nm with a shoulder visible at 720 nm. TEM spectra show that the particle size is in the range 35 to 100 nm. Using the ethanol suspension of these particles, we have fabricated and characterized working OPV (organic photovoltaic) devices. This approach is shown to be an effective way to control active layer morphology in OPV devices.

Pembuatan Lapisan Tipis Berbahan Antosianin Beras Ketan Hitam (Oryza Sativa Glutinosa) Menggunakan Metode Spin Coating

Pembuatan lapisan tipis berbahan antosianin beras ketan hitam menggunakan metode spin coating telah berhasil dilakukan. Penelitian ini bertujuan untuk membuat lapisan tipis dengan permukaan yang homogen. Lapisan tipis tersebut dibuat dengan memanfaatkan larutan antosianin dengan variasi konsentrasi 2,61%; 2,64%; dan 3,60% yang didepositkan pada substrat kaca berukuran 2,5 cm x 2,5 cm x 0,2 cm dengan kecepatan spin masing-masing sebesar 400, 500, 600, 700, 800, 900 dan 1000 rpm selama 60 detik. Sampel lapisan tipis yang dihasilkan diamati homogenitasnya dengan mikroskop binocular, dan diukur absorbansi nya dengan spektrofotometer UV-vis. Dari hasil penelitian, sampel yang menunjukkan kualitas terbaik ialah pada konsentrasi 3,6% yang diputar pada kecepatan 900 rpm selama 60 detik. Sampel ini memiliki homogenitas yang baik dengan ketebalan 9,6 µm dan nilai absorbansi sebesar 0,135 a.u. Selanjutnya, pada sampel tersebut diteteskan larutan gula dengan variasi konsentrasi 20%, 35% dan 45% kemudian diukur absorbansi nya. Hasil Pengukuran menunjukkan bahwa nilai absorbansi meningkat dengan bertambahnya konsentrasi larutan gula. Hal ini menunjukkan bahwa lapisan tipis berbahan antosianin beras ketan hitam berpotensi untuk dimanfaatkan sebagai bioreseptor .