High Voltage Sensitivity of Organic Pyroelectric Sensors with Polarization Treatment during Evaporation Process

Control of molecular orientation and electric dipoles in a pyroelectric thin film is one of the most important factors to improve the performance of organic infrared ray (IR) sensors. In this study, we have controlled the molecular dipole in a vinylidene fluoride (VDF) oligomer thin film by applying electric field between micro-gapped comb-like electrodes during vacuum deposition. The dipoles in the normally oriented VDF oligomer were highly aligned to the applied electric field in in-plane direction. The pyroelectric IR sensors, fabricated by the oriented VDF oligomer thin film, exhibited the excellent performance even without the poling treatment after the film deposition. A voltage sensitivity of the sensor showed 1473 V/W at 1 Hz, which was much higher value than that of typical sensors applied with the post-poling (~ 200 V/W). The improvement of the sensitivity is considered to be caused by the reduction of injected charges on the poling treatment, which usually causes the suppression of the dipole fluctuations for temperature change.