Back-reflected performance-enhanced flexible perovskite photodetectors through substrate texturing with femtosecond laser.

: Recently, enhancing the performance of flexible perovskite photodetectors through facile and effective means has gained greater attention. In contrast to typical approaches through modifying light-active materials, we present here a simple but effective design by improving light-matter interactions through near-field optical interference on a back-reflected substrate, whose architecture includes a morphologically flat top surface and a back scattering surface textured with micro/nanostructures by the femtosecond laser direct writing. A CH3NH3PbI3 perovskite film and polyethylene terephthalate are selected as the light-active and base materials, respectively. Under a 1 V bias voltage actuation and 532 nm laser irradiation at an intensity of 10 mWcm-2, the flexible device exhibits an excellent performance in photoresponsivity (47.1 mAW-1), detectivity (3.7×1011 Jones) and on/off ratio (4600). Due to the near-field optical enhancement of the substrate and the strong light-matter interaction, the performance parameters above are enhanced by at least five times over a wide spectral range of 220-780 nm. Such enhancement behaviors are independent of active material properties and therefore can be compatible with other operations such as crystalline transformation, doping, and interface modification. Moreover, the alteration of stress distribution on the structured substrate facilitates the bending robustness and stability. These features highlight the potential of back-reflected design in the development of flexible perovskite photoelectric devices, which are especially suitable for large-scale industrial production.