Influence of a Solvent Trap in ITO/PEN Substrates on the Performance of Flexible Perovskite Solar Cells and Light-Emitting Diodes

Perovskite-based flexible optoelectronics has drawn increasing attention in various fields, including quantum dot displays, building-integrated photovoltaics, and wearable devices. Flexible and transparent electrodes with outstanding surface properties are required for the commercialization of such devices. In this regard, tin-doped indium oxide (ITO) is considered a suitable material. In device fabrication, cleaning and ultraviolet–ozone (UVO) treatment of ITO/polymer substrates are essential for the deposition of high-quality perovskite and charge transport layers. However, polymer substrates can easily swell in organic solvents during cleaning. The trapped solvents in the substrate are decomposed to radicals under UV irradiation and are then adsorbed onto the ITO surface. This leads to a significant increase in the sheet resistance and a downward shift of the Fermi level. However, complete removal of the trapped solvents leads to excellent retention of the electrical properties of ITO. The resulting power conversion efficiencies of perovskite solar cells are found to be 14.11% and 19.54% when the devices employ the substrate with and without trapped solvents during the UVO treatment, respectively. In addition, the luminances of perovskite light-emitting diodes designed on the two types of substrates are found to be 87.2 and 329.6 cd m–2 at 4 V, respectively.