Flexible image sensor array with bulk heterojunction organic photodiode

Abstract

Thick organic bulk heterojunction photodiodes with low dark current <1nA∕cm2 and efficient charge collection are reported. An electric field >1V∕μm is sufficient to achieve >75% charge collection in films of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene-vinylene] and [6,6]-phenyl-C61-butyric acid methyl ester blends up to 4μm thick, and the rate of photocurrent decay is reduced at saturation fields. The integration of a 4μm thick sensor layer onto a flexible amorphous silicon thin-film transistor backplane gave an image sensor array with 35% external quantum efficiency and noise equivalent power of 30pW∕cm2 at reverse bias voltage of −4V.

Charge-integrating organic heterojunction phototransistors for wide-dynamic-range image sensors

“…Up to now, only monolithically integrated solution-processed organic photodiodes (OPDs) and thin-film transistors (TFTs) have been shown to operate at video frame rates, which are on the order of 30 frames per second (f.p.s.) 9,24,25 . Monolithic integration of OPDs and TFTs is complicated by differences in geometries, electrodes and active layers, and requires heterogeneous assembly.…”

“…Dynamic range = 20 log 10 Irr max Irr min dB (4) In comparison, a conventional charge-integrating photodiode pixel architecture composed of a photodiode in series with a transistor 9,23,25 made of the same material set as the phototransistor has a dynamic range of 64 dB at 30 f.p.s., which is similar to the 70 dB of consumer-grade CMOS sensors 22 (see Supplementary Fig. 9 for photodiode-based pixel architecture and performance).…”

“…Printable photodetectors, including phototransistors and photodiodes, have potential for the creation of low-cost but high-performance image sensors on flexible substrates [4][5][6][7][8][9][10][11][12] , and could open new methods of imaging not possible with rigid substrates 13,14 . Phototransistors produce photoconductive gain, which is not seen in photodiodes, and results in external quantum efficiencies (EQEs) well over 100% (refs 15-20).…”

Fabrication and characterisation of hybrid photodiodes based on PCPDTBT–ZnO active layers

“…Organic or hybrid photodiodes (HPDs) using metal oxide acceptor materials could have a number of advantages over the inorganic technologies, including potentially low costs, solution processability and flexibility, which could enable photodiodes to be placed onto non-flat surfaces [1,2]. Previous reports of HPDs possess a reasonable on/off ratio of photocurrent during illumination when compared to the dark current (typically>2 orders of magnitudes) [3].…”

Enhancing spectral contrast in organic red-light photodetectors based on a light-absorbing and exciton-blocking layered system

“…[1][2][3] Much recent attention is being paid to photovoltaic ͑PV͒ cells, [4][5][6] and more recently to organic photodetectors ͑OPDs͒. [7][8][9][10][11][12] In contrast to OPDs, solar cells require a high conversion efficiency over the entire solar spectrum, which reaches significantly into the near-infrared, whereas organic semiconductors with narrow band gaps are still being developed intensively. 13,14 However, photodectors require light sensitivity of high and sensitive spectral regions of them depend on their applications.…”