Face-to-face transferred multicrystalline ITO films on colorless polyimide substrates for flexible organic solar cells

We report on the successful face-to-face transfer of crystalline ITO (c-ITO) films from Si wafers to flexible colorless polyimide (CPI) substrates for application in high-performance flexible organic solar cells (OSCs). By using an Ag sacrificial layer and by coating of a CPI solution onto high-temperature processed c-ITO films, the film can be directly transferred from a Si wafer to a flexible CPI substrate without changing its sheet resistance or optical transmittance. At the optimized thickness of 100nm, the transferred c-ITO film showed sheet resistance of 25.65Ω/square, optical transmittance of 83.8%, and critical bending radius of 5.5mm, which are acceptable values in the fabrication of flexible OSCs. The flexible OSCs fabricated on the transferred c-ITO anode exhibited good cell performance with a fill factor of 68.99 %, a short circuit current of 8.90mA/cm², an open circuit voltage of 0.821V, and a power conversion efficiency of 5.041 %, comparable to that of OSC with reference ITO/glass (5.67%). This indicating that transferred c-ITO film is a promising flexible and transparent anode for high performance FOSCs.