| 초록 |
We investigated the recovery mechanism of the fill factor (FF) in inverted polymer solar cells (I-PSCs) with a structure of indium tin oxide (ITO)/titanium sub-oxide (TiOx) and an active layer in the cathode side. After performing electrochemical impedance spectroscopy on the ITO/TiOx interface, we found that the improved interface of ITO/TiOx after UV irradiation is mainly responsible for the recovery of FF in the I-PSC devices. Further investigation of TiOx with respect to measurements of contact potential difference and transient photoconductivity revealed that increased electron density and trap-filling processes triggered by UV irradiation resulted in the rearrangement of the Fermi levels of the ITO/TiOx interface, thereby narrowing the Schottky barrier width. Therefore, the accumulated electrons at the ITO/TiOx interface can be freely collected onto the ITO electrode by tunneling the barrier, leading to a remarkable enhancement of FF in the I-PSCs irradiated by UV light. |
