High detectivity squaraine-based near infrared photodetector with nA/cm2 dark current

Abstract

We demonstrate an organic photodetector showing high detectivity (3.4×1012 Hz0.5 cm/W) at a wavelength of 700 nm, based on squaraine/phenyl-C61-butyric-acid-methyl-ester bulk-heterojunction active material. This result is achieved by suppressing the device dark currents while simultaneously preserving its external quantum efficiency, as high as 15% at 700 nm. To this aim, a thin cross-linked film based on poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene-vinylene] is exploited to suppress electron injection from the device anode into the organic blend, thus reducing the dark currents by a factor of 30, to the extremely low value of 2 nA/cm2. Also, the detector bandwidth (∼1 MHz) is unaffected by the introduction of a blocking layer.

A hybrid CMOS-imager with a solution-processable polymer as photoactive layer

“…To demonstrate the ease of switching the material system to extend the absorption to the NIR region, we added a SQ dye 12,[44][45][46] as additional donor material to the PCBM:P3HT solution to exploit the absorption spectrum of SQ between 600 and 900 nm. About solar cells and photodetectors with a bulk-heterojunction active layer of PCBM:SQ, it was already reported [44][45][46] . In the Supplementary Discussion we report about the fabrication of large scale reference photodetectors to determine an optimal mixing ratio for a PCBM:P3HT:SQ detector.…”

Extremely Low Dark Current, High Responsivity, All‐Polymer Photodetectors with Spectral Response from 300 nm to 1000 nm

“…[ 4,18 ] One reason might be attributed to the lack of proper low-bandgap organic materials with high absorption coeffi cient and mobility for effi cient light harvesting and charge transport. [ 14,19 ] Another lies in the unavoidable contact of both donor and acceptor materials with the electrodes in a bulk hetero junction structure, which leads to the low shunt resistance and subsequent the large dark current injection under reverse bias. [ 14,20 ] As a major source of the device noise, a large dark current density would worsen the sensitivity and increase the power consumption.…”

“…[ 14,19 ] Another lies in the unavoidable contact of both donor and acceptor materials with the electrodes in a bulk hetero junction structure, which leads to the low shunt resistance and subsequent the large dark current injection under reverse bias. [ 14,20 ] As a major source of the device noise, a large dark current density would worsen the sensitivity and increase the power consumption. [ 14 ] Gong et al reported a polymer photodetector with broad spectral response from 300 to 1100 nm, based on a narrowbandgap polymer blended with a fullerene derivative.…”

“…[ 14,20 ] As a major source of the device noise, a large dark current density would worsen the sensitivity and increase the power consumption. [ 14 ] Gong et al reported a polymer photodetector with broad spectral response from 300 to 1100 nm, based on a narrowbandgap polymer blended with a fullerene derivative. [ 13 ] The dark current was dramatically suppressed by three orders of magnitude, when both hole and electron injection blocking layers were introduced.…”

“…[1][2][3] Recent years have witnessed numerous organic and organic/inorganic hybrid photodetectors with wide response spectrum, [4][5][6][7] high external quantum effi ciency (EQE), [7][8][9][10][11][12] low dark current density, [ 4,[13][14][15] as well as fast response time, [ 16,17 ] fabricated either by vacuum evaporation or solution processing.…”