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 of redox couples. Anodic or cathodic photocurrent was observed to be strongly dependent on the variables such as the bias potential and the type of redox couples such as hydroquinone and benzoquinone. In Chapter 6: The illuminated electrode in a symmetric photocell with an ITO/Organic Semiconductor/ITO structure can act as a photocathode or a photoanode depending on both the orbital energy levels of melt-inserted organic compounds and the work function ($＼phi_ITO$) of electrodes. In Chapter 7: A solid-state photoelectrochemical cell was fabricated with perylene-3,4,9,10-tetracarboxylic acid (PTCA)-sensitized nanostructural $SnO_2/ITO$ electrode and poly(vinylidene fluoride-co-hexafluoropropylene) [P(VdF-co-HFP)]-based gel polymer electrolyte (GPE). The cell with an $ITO/SnO_2(PTCA)/GPE/Pt$ structure, showed a short circuit photocurrent density of 2.5 mA/㎠, an open circuit photovoltage of 0.28 V and a fill factor of 0.51 under illumination of white Xe light with an intensity of 100 mW/㎠. The incident photon to current efficiency of the device was 16.3 % under 480 nm monochromatic lights with an intensity of 0.56 mW/㎠. In Chapter 8: Cadmium telluride (CdTe) nanorod was synthesized and characterized by optical and electrochemical methods. The characteristics of photovoltaic device using CdTe nanorod blended with poly(3-hexyl thiophene) (P3HT) was studied. The device with an ITO/PEDOT(PSS)/CdTe+P3HT/Al structure showed a short-circuit photocurrent density of 35μA/㎠ and an open-circuit photovoltage of 0.74 V under white Xe light with an intensity of 30 mW/㎠. In Chapter 9: Conclusive remarks were made as a result of this thesis and for future recommendable research direction.