Strain‐Tolerant, High‐Detectivity, and Intrinsically Stretchable All‐Polymer Photodiodes

A skin‐like photodiode (PD) that is stretchable and skin‐conformable is crucial to opening the next‐generation wearable electronics for optical biometric monitoring, biomedical imaging, and others. To achieve reliable PD characteristics under large deformation, stretchable PDs with high detectivity and high mechanical stretchability must be developed. Herein, intrinsically stretchable polymer‐based PDs (is‐PPDs) comprising all‐polymeric constituent layers are demonstrated. In particular, elastomeric photoactive layers consisting of an elastomer with p‐/n‐type semiconducting polymers and conducting polymer‐based stretchable transparent electrodes with modulated work functions improve both the mechanical stability and the detectivity (D*) of is‐PPDs. Accordingly, is‐PPDs show excellent D* over 1013 Jones with a suppressed dark current density of 0.1 nA cm−2 before and after 100% stretching. The proposed is‐PPDs record high‐quality and stable photoplethysmography signals at the wrist with outward extension. A skin‐like all‐polymer‐based photodiodes with excellent intrinsic stretchability and high‐detectivity is successfully demonstrated.