<p>Planar-structured amorphous InGaZnO (a-IGZO) film-based UV photodetectors with different ITO interdigitated electrode spacings were developed on flexible PI substrates via radio frequency magnetron sputtering and non-lithographic fabrication processes. The effects of oxygen flow rate on the surface morphology, electrical transport, and chemical bonding properties of the a-IGZO films were systematically investigated to optimize the performance of the flexible detector. The average transmittance of the flexible a-IGZO photodetector is over 90% in the visible spectral range with a large photo-to-dark current ratio of 3.9×10³ under 360 nm UV illumination. The photocurrent of the detectors increases with decreasing the electrode spacing, which is attribute to formation of higher electrical field and drifting more electron-hole pairs to the electrode with shortening the electrode spacing. Under a UV illumination intensity of 9.1 mW/cm², the highest responsivity and detectivity of the photodetector with the electrode spacing of 0.4 mm reach 62.1 mA/W and 2.83 × 10¹¹ cm·Hz^1/2·W⁻¹ at 11 V bias voltage, respectively. The flexible detector exhibits enhanced photoresponse performance with the rise and decay time of 2.02 and 0.94 s, respectively. These results can be used in a practical scheme to design and realize the a-IGZO based UV photodetectors with excellent transparency and flexibility for wearable UV monitoring applications.</p>