Characterization and analysis of pentacene and oxide thin films for an organic-inorganic heterojunction diode photodetector application

Ahmad, Fatin Nor (2022) Characterization and analysis of pentacene and oxide thin films for an organic-inorganic heterojunction diode photodetector application. Masters thesis, Universiti Tun Hussein Onn Malaysia.


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Organic and inorganic materials have recently received research interest in the optoelectronic field that can combine the merits like mechanically flexibility and function tunability of organic materials and broadband absorption, excitonic mechanisms, and high carrier mobility of inorganic materials. Organic devices lag behind in terms of performance due to low carrier mobility, low efficiency in charge carrier injection and stabilities. Therefore, the characterisation and analysis of pentacene and zinc oxide (ZnO) thin films for an organic-inorganic heterojunction-based p-n junction diode are discussed in this study for photodetector application. The pentacene thin films were deposited using thermal evaporation, while ZnO thin films were deposited using RF magnetron sputtering with various deposition durations at room temperature. Both thin films were investigated by X-ray diffraction (XRD) and atomic force microscopic (AFM) to reveal the film’s molecular and structure orientation depending on deposition time. When the deposition time increased, the pentacene thin films exhibited high crystallinity with large grain size and roughness. The films showed strong absorption at 60 minutes of deposition with a small bandgap of 1.79 eV. Meanwhile, ZnO films showed high crystallinity with a small crystallite size and high transmittance in 60 minutes for a bandgap of 3.15 eV. A pentacene-ZnO-based p-n junction device was fabricated when the voltage of -0.8 V and 0.2 V were applied, and the current value for the photodetector was measured as 3.63  10-12 A and 7.39  10-11 A, respectively. Furthermore, impedance analysis of the p-n junction devices showed impedance is significantly reduced at 3.0 V and remained unaffected by the low voltage, which indicated that charge carriers are being carried through the system due to the reverse bias condition of a photodetector. For instance, the other heterojunction layer of organic/lead sulfide (PbS) has been reported to have great potential in upcoming optoelectronic applications. However, the integration of the proposed structure, which is pentacene and ZnO with a heterojunction layer in a p-n junction device, could be useful for organic-inorganic photodetector devices. The p-n junction device was successfully fabricated using a suitable deposition technique.

Item Type: Thesis (Masters)
Subjects: T Technology > T Technology (General)
Divisions: Faculty of Electrical and Electronic Engineering > Department of Electrical Engineering
Depositing User: Mrs. Sabarina Che Mat
Date Deposited: 07 Feb 2023 03:41
Last Modified: 07 Feb 2023 03:41

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