Effects of Ar ion beam treatment on properties of roll-to-roll sputtered Sn-doped In2O3 films on colorless polyimide substrate

We report on the effects of Ar ion beam treatment on the electrical, optical, and mechanical properties of flexible Sn-doped In2O3 (ITO) films grown on colorless polyimide (CPI) by roll-to-roll (R2R) sputtering. Effective Ar ion beam treatment on ITO films led to the reduction of sheet resistance without degradation of optical transmittance of ITO films even though they were prepared at room temperature. In addition, Ar ion beam treatment resulted in crystallization of the R2R-sputtered ITO films without intentional substrate heating. At optimized conditions, the Ar ion beam treated ITO film showed a sheet resistance of 54.6 Ω/square and an optical transmittance of 80.1%. A flexible organic solar cell (FOSC) fabricated with the Ar ion beam treated ITO film exhibited a power conversion efficiency (PCE) of 3.137%, which was higher than that of a FOSC made with untreated ITO film. This indicates that the in-situ Ar ion treatment is a promising method for fabrication of crystalline ITO films on flexible substrates without intentional substrate heating in a R2R sputtering process.