Air-stable, high current density, solution-processable, amorphous organic rectifying diodes (ORDs) for low-cost fabrication of flexible passive low frequency RFID tags
Abstract We report on long-term air-stable organic rectifying diodes (ORD) on flexible substrates based on a solution deposited amorphous organic semiconductor (OSC) material, consisting of a co-polymer of arylamine and a fused aromatic species, reaching charge-carrier mobilities of μ = 0.05 cm2/V s (space charge limited current region) and current densities of up to 100 A/cm2 at 10 V levels with rectification ratios of 104 operating in the 10 kHz range. The ORDs exhibit a high degree of air-stability without any passivation with extremely reliable reproducibility. ORDs were fabricated on polyethylene naphthalate foils in a vertical sandwich structure with gold and aluminium as the injecting and blocking electrodes respectively via evaporation with the OSC spin-coated in between (Type1). In order to improve device performance of the ORDs, poly(ethylenedioxythiophene):poly(styrenesulfonate) was μ-dispensed as a hole-injection layer (Type2). The results for Type1-diodes show a really narrow spread of the diode characteristics, whereas for Type2 diodes the spread is slightly more but still acceptable. These ORDs prove themselves better than conventional pentacene diodes both in terms of reliability/repeatability of the diode performance and air-stability without an encapsulation layer, and goes towards the enabling of a viable and reliable low-cost fabrication method of radio frequency identification-tags using organic semiconductors.