title: Effect of organic solar cells using various power O2 plasma treatments on the indium tin oxide substrate.
abstract: The effect of organic solar cells (OSCs) by using different power O2 plasma treatments on indium tin oxide (ITO) substrate was studied. The power of O2 plasma treatment on ITO substrate was varied from 20W to 80W, and the power conversion efficiency of device was improved from 1.18% to 1.93% at 20W O2 plasma treatment. The function of O2 plasma treatment on ITO substrate was to remove the surface impurity and to improve the work function of ITO, which can reduce the energy offset between the ITO and SubPc layer and depress the leakage current of device, leading to the shunt resistance increased from 897 to 1100Ωcm(2). The surface roughness of ITO decreased from 3.81 to 3.33nm and the work function of ITO increased from 4.75 to 5.2eV after 20W O2 plasma treatment on ITO substrate. As a result, the open circuit voltage and the fill factor were improved from 0.46 to 0.70V and from 0.56 to 0.61, respectively. However, the series resistance of device was dramatically increased as the power of O2 plasma treatment exceeds 40W, leading to the efficiency reduction. The result is attributed to the variation of oxygen vacancies in ITO film after the 60, 80W O2 plasma treatment. As a consequence, the power of O2 plasma treatment on ITO substrate for the OSCs application should be controlled below 40W to avoid affecting the electricity of ITO film.
authors.affiliation: Institute of Microelectronics, Department of Electrical Engineering, National Cheng-Kung University, #1 University Rd., Tainan, Taiwan.
authors.forename: Jhong-Ciao
authors.initials: JC
authors.lastname: Ke
authors.affiliation: Institute of Microelectronics, Department of Electrical Engineering, National Cheng-Kung University, #1 University Rd., Tainan, Taiwan.
authors.forename: Yeong-Her
authors.initials: YH
authors.lastname: Wang
authors.affiliation: Department of Electronic Engineering, Fortune Institute of Technology, Kaohsiung 83160, Taiwan.
authors.forename: Kan-Lin
authors.initials: KL
authors.lastname: Chen
authors.affiliation: Department of Applied Physics, National University of Kaohsiung, Nanzih, Kaohsiung, Taiwan. Electronic address: chien@nuk.edu.tw.
authors.forename: Chien-Jung
authors.initials: CJ
authors.lastname: Huang
keywords: Indium tin oxide; O(2) plasma; Organic solar cell