Reduced leakage current and improved performance of an organic photodetector using an ytterbium cathode interlayer

초록

We report the electron transport and hole-blocking properties of ytterbium, which make it suitable for use as the cathode interlayer for the poly(3-hexylthiophene-2,5-diyl) (P3HT):phenyl-C61-butyric acid methyl ester (PCBM) bulk heterojunction in organic photodetectors (OPDs). The final device structure consisting of ITO/NiOx/P3HT:PC60BM/Yb/Al is compared to devices with Ca as the cathode interlayer and without a cathode interlayer. The performance of OPDs is analyzed, and effective carrier extraction and hole blocking are confirmed through the dynamic characteristics of the devices. The use of a Yb layer in the OPDs improves the resistance, thereby improving the carrier extraction and decreasing the leakage current significantly. A figure of merit for the dynamic characteristics, namely the bandwidth of Yb, is improved owing to the fast response time. The bandwidth exceeds 100 kHz at a relatively low light intensity. Optical-electrical measurements are performed, and J-V characteristics, impedance, and dynamic characteristics are analyzed. We investigate the effects of the Yb layer on the performance of the OPDs, focusing on its carrier extraction, leakage current, and resistance components.

키워드