Photoelectrochemical and optoelectronic processes in organic thin films and inorganic nanocrystals

Abstract

This thesis have focused on the organic thin film and inorganic nanocrystals for photovoltaic device application. In Chapter 2: An organic photovoltaic cell was fabricated, with the configuration ITO/zinc phthalocyanine (ZnPc)/N,N``-diheptyl-3,4,9,10-perylenebiscarboximide (PTCDI-C7) (PTCDI) /Ga:In. PTCDI is a liquid crystal and acts as an electron acceptor organic material while ZnPc corresponds to a donor. The cell performance under illumination was examined with different organic layer thickness. A cell incorporating 25 nm thick organic layers showed a short circuit photocurrent ($I_SC$) of 1.6mA/㎠, an open circuit photovoltage ($V_OC$) of 0.6 V, and a fill factor (FF) of 0.4 with white Xe light illumination (wavelength≥400 nm) with an intensity of 100mW/㎠. In Chapter 3: Molecular orbital energy levels of perylene-bis(phenylbutylimide) (PPBI) were estimated by electrochemical and optical methods. Then the photo-device with an ITO/PPBI/Al structure, was fabricated to measure charge mobility by time-of-fight techniques. Electron was observed to be faster than holes, which display that PPBI is an n-type organic semiconductor. When the evaporated film on PPBI on ITO was annealed and fabricated as a device, the electron mobility was decreased. In Chapter 4: An organic photocell with an ITO/N,N``-diheptyl-3,4,9,10-perylenebiscarboximide (PTCDI-C7)/Al structure was fabricated to measure charge mobility by time-of-fight techniques. Electrons were observed to be faster than holes due to its n-type characters. Furthermore, a photocell incorporating an annealed PTCDI-C7 film showed an improved mobility due to better organized structure originating from its liquid crystalline (LC) characters. In Chapter 5: N,N``-dioctadecyl-3,4,9,10-perylenebiscarboximide thin film on ITO glass, produced a photocurrent, when immersed in an electrolyte solution containing a redox couple and illuminated. The photocurrent was investigated against bias potential, and concentration and type ...