Organic Ultraviolet Photodetectors Exhibiting Photomultiplication, Low Dark Current, and High Stability. Issue 8 (30th May 2017)

• Record Type: Journal Article
• Authors: Esopi, Monica R.; Calcagno, Max; Yu, Qiuming
• Is Part Of: Advanced materials technologies. Volume 2:Issue 8(2017)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2017-05-30
• Subjects: dark currents -- organic photodetectors -- photomultiplication -- UV‐selective; Materials science -- Periodicals; Technological innovations -- Periodicals; Materials science; Technological innovations; Periodicals; 620.1105
• DOI: 10.1002/admt.201700025
• Languages: English
• ISSNs: 2365-709X

Abstract

Abstract : Organic UV photodetectors can provide a cheap, durable alternative to current technologies used for applications such as missile detection and arc flash protection. The wide‐bandgap semiconductor poly[(9, 9‐dioctylfluorenyl‐2, 7‐diyl)‐alt‐co‐(bithiophene)] (F8T2), combined disproportionately with the fullerene‐derivative [6, 6]‐phenyl‐C71 ‐butyric acid methyl ester (PC71 BM) in weight ratios of 100:4 and 100:1, comprises the active layers of organic UV photodetectors. The small clusters of PC71 BM trap charges, enhancing band bending and charge injection and thus enabling photomultiplication. These clusters also prevent electrons from transporting through the device, helping produce a low dark current. Although devices without an electron transfer layer (ETL) exhibit more efficient photomultiplication, they tend to be unstable. Devices with a F8T2:PC71 BM weight ratio of 100:4 and with an ETL demonstrate an external quantum efficiency peaking at 5600%, at 360 nm and −40 V bias, and a low dark current of 2.7 × 10 −7 mA cm −2 at −1 V bias. These devices are stable and behave well even under strong biases, which enhance the UV‐selectivity and response speed of the devices. Abstract : A UV‐selective, stable organic photodetector achieves high external quantum efficiency via photomultiplication. Isolated fullerene‐derivative clusters embedded in a wide‐bandgap polymer matrix trap electrons upon light illumination, resulting in band bending and charge injection under reverse biases. The low dark current is maintained by the high hole injection barrier and the lack of a electron pathway.