Interfacial fluorinated polymer layer enabling highly stable, fast response, high-performance self-powered PEA2PbBr4 ultraviolet photodetector

A fast-response, self-powered UV photodetector is highly desirable in health and safety applications to monitor UV exposure, especially to the human body. PEDOT: PSS is known as an effective hole transport layer often used in the fabrication of organic electronics. However, the moisture-sensitive PEDOT: PSS resulted in poor surface coverage and degradation of perovskite material, leading to lower performance and instability of the device. In this work, adding hydrophobic Nafion layer on top of PEDOT: PSS and perovskite interface dramatically increased the photocurrent and stability. The best device based on PEA2PbBr4 films with a Nafion layer exhibited a high photocurrent of 0.34 mA/cm2 and a fast response speed of 15.6 μs at 0 V bias. The responsivity and detectivity of the optimized device were calculated to be 25 mA/W and 2.54 × 1011 Jones, respectively. The improved device performance is a direct result of the enhanced surface coverage as shown by field-emission scanning electron microscope and energy dispersive x-ray spectroscopy. Furthermore, the PEA2PbBr4 films and devices based on Nafion coated PEDOT: PSS showed a better UV light stability than those without the Nafion layer due tothe hydrophobic nature of the Nafion layer. As a result of this simple technique, high-performance PEA2PbBr4 photodetector can be fabricated.