Flexible near-infrared organic photodetectors based on a high work function anode

Flexible near-infrared (NIR) organic photodetectors (OPDs) are promising for health monitoring and wearable electronic applications but suffer from poor sensitivity related to the low work function anode. In this study, we developed flexible NIR OPDs based on a high work function PEDOT:PSS anode. The optimized PEDOT:PSS anode (SFD-PH1000) exhibits a high conductivity of 4400 S cm-1 on the PEN substrate and a high work function of 5.07 eV, which effectively blocks reverse electron injection in OPDs. As a result, the flexible NIR OPD based on an SFD-PH1000 anode exhibits one order of magnitude reduction in dark current density and a three-time increase in specific detectivity compared with that based on the traditional ITO anode. The SFD-PH1000-based flexible OPD also shows markedly superior mechanical flexibility and can monitor heart rate and blood oxygenation in photoplethysmography test with an error less than 3%. Flexible near-infrared organic photodetectors with an optimized PEDOT:PSS anode present more sensitive detectivity than the control flexible device with the traditional ITO anode and achieve heart rate and blood oxygen saturation monitoring.