Author(s): Im, D., H. Moon, M. Shin, J. Kim, S. Yoo
Journal: Advanced Materials (2011) 23 (5): 644-648.
Organic diodes have recently received considerable attention as components in low-cost high-speed rectifiers that provide DC power to passive radio-frequency identification (RFID) tags, which do not have on-board power sources. [ 1 ] Both vertical diode structures [ 2 , 3 ] and “diode-connected” thin-fi lm transistor (TFT) structures [ 4 ] have been used in organic-based rectifiers that are operable at 13.56 MHz, which is the current standard carrier frequency for low-cost passive RFID tags. While 13.56 MHz operation may suffice for many applications, long-range tag
identification, which is an essential feature that differentiates RFID technology from barcode-based systems, demands faster operation speeds in the ultrahigh frequency (UHF) range because electromagnetic (EM) wave methods can be combined with reasonably sized antennas in this frequency range. [ 2 , 5 ] With this motivation, much effort has been applied toward extending the operational bandwidth of organic diodes and rectifiers ultimately to the UHF range. [ 6 ] Identifying semiconductor materials with high carrier mobilities and device architectures that yield ideal diode characteristics with a high rectification ratio are among the key considerations in such efforts.