Dependence of ITO‐Coated Flexible Substrates in the Performance and Bending Durability of Perovskite Solar Cells

Flexible perovskite solar cells (PSCs) is being reported on different kinds of indium tin oxide (ITO)‐coated flexible substrates such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) with varying sheet resistance. High sheet resistance and low transmittance of these substrates in comparison to glass‐ITO based rigid substrate are among the major issues in achieving high power conversion efficiency (PCE), especially with large active area due to considerably low fill factor (FF) values. With a small active cell area of 0.1 cm2, it is found that sheet resistance of these substrates do not play a dominant role and the short circuit current density (JSC) depends on the transmittance of these conducting flexible substrates producing average PCE of 12.1% with PEN‐ITO (12 Ω/□) and 11.74% for PET‐ITO (49 Ω/□). When the active cell area is increased to 1 cm2, sheet resistance seems to play a major role to maintain JSC as well as FF of the flexible PSCs giving PCE of ∼10% with PEN‐ITO (12 Ω/□) in comparison to 3.4% for PET‐ITO (49 Ω/□). In contrast to PCE results, bending durability test for 1000 cycles showed that the flexible substrates with highest sheet resistance can retain maximum PCE.