Flexible Sandwich Photodetectors Based on Thick Polythiophene Films

We report a flexible photodetector with a sandwich structure of Au/polythiophene (PTh)/Au, which consists of two Au electrodes with a thickness of 30 nm each and a PTh layer with a thickness of 10−40 μm. The devices showed strong and fast photoresponses under excitation through the gold electrodes using white light or a 514 nm laser beam. Upon illumination with a 40 mW/cm 2 514 nm laser beam and under a low bias electric field of 0.2 V/μm, the device with a 20 μm thick PTh layer exhibited an external quantum efficiency up to 136%. These devices are flexible and can be bent to large angles and fabricated into large sizes with arbitrary shapes.