Organic Photodetectors with Gain and Broadband/Narrowband Response under Top/Bottom Illumination Conditions

摘要

Organic photodetectors (OPDs) possessing broadbandarrowbandrnphotodetection capability and gain have great potential in integratedrnoptoelectronics products. In this work, OPDs with a device structure ofrnITO/poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)/rnthick active layer/semitransparent Al electrode exhibit the extraordinaryrnfunctions, gain and bidirectional photodetection capability with tunablernspectral response range. For the binary OPDs with poly(3-hexylthiophene-rn2,5-diyl) (P3HT):[6,6]-phenyl-C_(71)-butyric acid methyl ester (PC_(71)BM) (100:1,rnwt/wt) as active layer, the OPDs exhibit narrowband response from 620 torn700 nm with full-width at half maximum (FWHM) of ≈30 nm under bottomrnillumination condition and broadband response from 300 to 700 nm underrntop illumination condition, respectively. To further confirm and optimizernthe extraordinary functions of OPDs, ternary devices are fabricated withrnP3HT:poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene-rnco-3-fluor-othieno[3,4-b]thiophene-2-carboxylate] (PTB7-Th):PC_(71)BMrn(50:50:1, wt/wt) as active layer. The narrowband response can be adjustedrnto near infrared (NIR) region from 760 to 860 nm. The broadband responserncan be extended to NIR region with response range from 300 to 860 nm.rnMeanwhile, external quantum efficiency (EQE) spectral shape of the ternaryrnOPDs becomes flatter under top illumination condition and can be keptrnconstant under different bias. The ternary OPDs exhibit similar EQE valuesrnof ≈2000% and specific detectivity larger than 10~(11) Jones at −50 V bias underrnbottom and top illumination conditions.