Sandwiched Structure Design for Perovskite Solar Cells with Improved Folding and Environmental Stability

Foldable perovskite solar cells (PSCs) have promising applications in self-powered wearable and portable electronic devices. However, the folding stability requires further improvement through mitigating the strain in brittle layers under folding deformation. Herein, sandwich-structured PSCs (SS-PSCs) are constructed by coating a protection layer at the back of the device, to tune the neutral plane (NP) place into the brittle perovskite films. To accurately regulating the NP place, the effect of protective layer thickness on the strain distribution in PSCs is simulated. The SS-PSCs are experimentally prepared using Al2O3/polyethylene terephthalate (PET) protection layer with optimum thickness, combined with ultrathin silver foldable electrodes. Benefitting from the water-resisting Al2O3/PET, the SS-PSCs demonstrate high environment stability which maintains 85.1% of original efficiency after 700 h in humidity of 50% +/- 10%. More importantly, the SS-PSCs exhibit excellent mechanical stability, which maintains >90% of the initial efficiency after bending with 4000 cycles at radius of 0.2 mm, and even 67.2% of the initial efficiency after 50 direct folding cycles. As far as it is known, it is one of the best mechanical stable devices. The findings pave the way for realizing not only foldable PSCs but also other foldable optoelectronic devices, such as sensors and organic light emitting devices.