[11a-M136-1~10] 12.3 Functional Materials and Novel Devices

▼ [11a-M136-8] Fast and Sensitive Near Infra-Red Photodetector Based on a Liquid Crystalline Phthalocyanine Derivative

〇(M1)Shahriar Kabir¹, Yukiko Takayashiki¹, Jun-ichi Hanna¹, Hiroaki Iino¹ (1.Tokyo Tech)

Keywords:Organic photodetector, Organic semiconductor, NIR photodetector

In this work, we used a blend of 1,4,8,11,15,18,22,25-octaocltyl-phthalocyanine (8H₂Pc) and 1-(3-methoxy-carbonyl)-propyl-1-1-phenyl-(6,6)C61 (PCBM) to prepare vertical inverted photodiode. The blend ratio of 8H₂Pc:PCBM was 1:1 by weight and the device structure was ITO/PEIE/8H₂Pc:PCBM/MoO₃/Au with active area of 4mm². The photodetector showed low dark current density, in the range of nA/cm², because of careful surface modification of the ITO electrode with polyethylenimine (PEIE) solution. The performance of the detector was evaluated by 740nm NIR irradiation with light intensity of 8mW/cm². The detector showed good detectivity, D* = 2.6×10¹¹cmHz^1/2/W, noise equivalent power, NEP = 5.1×10^-14W/Hz^1/2 and J_ph/J_d ratio = 1.5×10⁴ at -4V bias. The rise and fall time between 10% and 90% of the steady state values of dark current and photo current was 58µsec at -6V bias. This fast response time was possible after annealing the device at 120°C, the liquid crystal phase temperature of 8H₂Pc.