TIPS Pentacene as a Beneficial Interlayer for Organic Photodetectors in Imaging Applications

The small molecule 6,13-bis (triisopropylsilylethynyl) (TIPS) pentacene has been used as an interlayer for the reduction of dark currents in organic photodetectors (OPDs) based on a bulk heterojunction of poly-3-hexyl-thiophene (P3HT) and [6, 6]-phenyl C61 butyric acid methyl ester. We report OPDs with dark currents of ~0.9 nA/cm
²
at -5 V and external quantum efficiencies close to 80% at 530 nm. Compared to the reference, P3HT interlayer, TIPS pentacene shows a significant increase of the OPD's detectivity from 3.29 × 10
¹²
to 1.63 × 10
¹³
Jones. Also, the OPD's dynamic range is improved reducing the limit of signal detection from 132 to 6.3 nW/cm
²
under green light irradiation. Singular hysteresis in the I-V characteristic curve has been observed and impedance spectroscopy measurements were carried out to analyze its origin and generate a replacement electrical model for the device at reverse bias. Finally, OPDs with TIPS pentacene interlayer have been integrated on top of amorphous silicon thin-film transistor backplanes to obtain the first OPD-based image sensor using this interlayer.