Texture-enhanced Mechanical Stability of Transparent Electrodes for Flexible Optoelectronics with Near-infrared Response

Transparent electrodes with high conductivity and mechanical robustness are essential for flexible opto-electronic applications. Indium tin oxide (ITO) single layers have long been considered as unsuitable for flexible applications due to their brittleness. Here, it is shown that their mechanical stability can be substantially enhanced by texturing the flexible substrate. First, the opto-electronic performance of single ITO layers and ITO/Ag/ITO stacks on polyethylene terephthalate (PET) foils is evaluated numerically by means of Haacke's figure-of-merit. Single ITO layers are found to be the electrode of choice for applications with a near-infrared response due to their superior transparency. Following this, the sheet resistance of ITO layers is experimentally investigated on textured PET upon deformation parallel and perpendicular to a 1D texture grating. An "accordion-like" deformation perpendicular to the grating and high texture aspect ratios are shown to avoid crack formation and loss of conductivity in the ITO. Simulations prove the considerably reduced occurrence of mechanical stress in this case. It is further experimentally demonstrated that texturing foils increase transmittance and haze. The enhanced mechanical robustness and optical performance by using textured foils make single ITO layers promising candidates for flexible opto-electronic applications with a near-infrared response, such as all-perovskite tandem solar cells, thermal sensors, and photodetectors.