Previous study showed that the introduction of solution-dispersed copper iodide (CuI) as anode buffer layer has improved the performance of inverted type organic solar cell. However, the CuI preparation parameters have yet to be optimized for the inverted type organic solar cell. In this work, the effect of ultrasonic agitation of CuI solution on inverted type organic solar cell based on zinc oxide (ZnO)/poly(3-hexylthiophene) (P3HT):(6,6)-phenyl-C61-butyric acid methyl ester (PCBM) has been studied. ZnO, acting as electron transporter, was spin-coated on top of fluorine tin oxide (FTO) substrate, while the active layer consisting of P3HT:PCBM as the electron donor and electron acceptor was spin-coated onto the ZnO layer and the top electrode, silver (Ag) was then thermally evaporated. CuI dispersed in acetonitrile solution was ultrasonicated with durations of 10, 20 and 30 min and then was spin-coated on the active layer. It was found that solution-dispersed CuI with longer ultrasonic agitation duration attained a relatively higher PCE than that with shorter duration and the highest PCE was 2.13%, achieved at 30 min ultrasonic agitation due to good film surface morphology. For further optimization, the deposition of CuI was carried out using different spin coating speeds of 1000 and 3000 rpm. The optimum PCE obtained was 2.29 at a spin coating speed of 3000 rpm as a result of uniform layer of CuI.
