High-performance deep ultraviolet DUV photodetectors operating at ambient conditions with < 280 nm detection wavelengths are in high demand because of their potential applications in diverse fields. We demonstrate for the first time, high-performance flexible DUV photodetectors operating at ambient conditions based on quantum dots QDs synthesized by femtosecond-laser ablation in liquid FLAL technique. Our method is facile without complex chemical procedures, which allows large-scale cost-effective devices. This synthesis method is demonstrated to produce highly stable and reproducible ZnO QDs from zinc nitride target Zn3N2 without any material degradation due to water and oxygen molecule species, allowing photodetectors operate at ambient conditions. Carbon-doped ZnO QD-based photodetector is capable of detecting efficiently in the DUV spectral region, down to 224 nm, and exhibits high photo-responsivity and stability. As fast-response of DUV photodetector remains significant parameter for high-speed communication; we show fast-response QD-based DUV photodetector. Such surfactant-free synthesis by FLAL can lead to commercially available high-performance low-cost optoelectronic devices based on nanostructures for large scale applications.