Enhanced UV Photodetection with Efficient and Stable ZnO Nanoparticles Passivated‐CsPbBr ₃ Perovskite Nanocrystals

Silicon (Si) photodetectors (PDs) demonstrate low UV responsivity due to the higher surface absorption losses and low‐penetration depth of high‐energy photons. Strong solar blind optical downconverters that absorb in the UV range and downconvert to emit in the visible range can help improve the UV response of the Si‐PDs. Solution‐processed cesium lead bromide (CsPbBr 3 ) perovskite nanocrystals (NCs) show efficient optical downconversion from UV to the visible region. Herein, using ZnO nanoparticle‐decorated highly luminescent and stable CsPbBr 3 NCs as UV light optical downconverters is reported. The ZnO‐mixed CsPbBr 3 NC‐based film shows higher visible photoluminescence quantum yield (PLQY) and efficient UV‐to‐visible optical downconversion compared to the pristine CsPbBr 3 NC‐based film. The Si‐PDs coated with the ZnO‐passivated high PLQY perovskite NCs demonstrate more than 1000% improvement in responsivity at 290 nm excitation wavelength without impacting the visible detectivity of the bare Si‐PDs. Overall, it maintains more than 500% responsivity improvement in the UV‐C region. The downconversion layer does not significantly affect the modulation speed of the PDs. The ZnO‐mixed NC‐coated Si‐PDs maintain a high photostability under extremely humid conditions, resulting from NC structural degradation reduction with ZnO passivation.