Abstract
This paper reports the potential application of cadmium selenide (CdSe) quantum dots (QDs) in improving the microelectronic characteristics of Schottky barrier diode (SBD) prepared from a semiconducting material poly-(9,9-dioctylfluorene) (F8). Two SBDs, Ag/F8/P3HT/ITO and Ag/F8-CdSe QDs/P3HT/ITO, are fabricated by spin coating a 10 wt% solution of F8 in chloroform and 10:1 wt% solution of F8:CdSe QDs, respectively, on a pre-deposited poly(3-hexylthiophene) (P3HT) on indium tin oxide (ITO) substrate. To study the electronic properties of the fabricated devices, current-voltage (I–V) measurements are carried out at 25 °C in dark conditions. The I–V curves of Ag/F8/P3HT/ITO and Ag/F8-CdSe QDs/P3HT/ITO SBDs demonstrate asymmetrical behavior with forward bias current rectification ratio (RR) of 7.42 ± 0.02 and 142 ± 0.02, respectively, at ± 3.5 V which confirm the formation of depletion region. Other key parameters which govern microelectronic properties of the fabricated devices such as charge carrier mobility (µ), barrier height (ϕb), series resistance (Rs) and quality factor (n) are extracted from their corresponding I–V characteristics. Norde’s and Cheung functions are also applied to characterize the devices to study consistency in various parameters. Significant improvement is found in the values of Rs, n, and RR by 3, 1.7, and 19 times, respectively, for Ag/F8-CdSe QDs/P3HT/ITO SBD as compared to Ag/F8/P3HT/ITO. This enhancement is due to the incorporation of CdSe QDs having 3-dimensional quantum confinement and large surface-to-volume area. Poole-Frenkle and Richardson-Schottky conduction mechanisms are also discussed for both of the devices. Morphology, optical bandgap (1.88 ± 0.5 eV) and photoluminescence (PL) spectrum of CdSe QDs with a peak intensity at 556 nm are also reported and discussed.
Highlights
Junction between different materials has a vital role in electronic and optoelectronic devices and is, one of the significant parts that govern the performance of a device
The indium tin oxide (ITO)-coated glass was used as a substrate for Schottky barrier diode (SBD) that was cleaned in acetone and isopropanol by using ultrasonic bath for 10 min and dried under the continuous flow of dry nitrogen gas
The work carried out in this paper demonstrated enhancement in the microelectronic properties a SBD Ag/ F8-cadmium selenide (CdSe) quantum dots (QDs)/P3HT/ITO made from the polymer matrix F8 blended with CdSe QDs
Summary
Junction between different materials has a vital role in electronic and optoelectronic devices and is, one of the significant parts that govern the performance of a device. Polymeric semiconductors are of great interest due to their solution processability in many organic solvents and/or in water This property allows one to tune the properties of polymer as desirable by making blend/suspension with other functional materials and nanoparticles[9,10,11]. Blending nanoparticles into polymer matrix can lead to wonderful electronic and optoelectronic properties by virtue of high surface-to-volume ratio of the nanomaterials. By spin coating F8-CdSe QD nanocomposite solution, Ag/F8-CdSe QDs/P3HT/ITO SBD is fabricated. An 80 nm thin film of F8-CdSe blend was deposited using the spin coating technique on the pre-coated P3HT layer over a glass substrate coated with ITO. The vacuum thermal evaporation was used to deposit a 60 nm thick Ag electrode on F8-CdSe active layer to complete the fabrication of Ag/F8-CdSe QDs/ P3HT/ITO SBD.
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