Multi-spectral imaging with infrared sensitive organic light emitting diode

Abstract

Commercially available near-infrared (IR) imagers are fabricated by integrating expensive epitaxial grown III-V compound semiconductor sensors with Si-based readout integrated circuits (ROIC) by indium bump bonding which significantly increases the fabrication costs of these image sensors. Furthermore, these typical III-V compound semiconductors are not sensitive to the visible region and thus cannot be used for multi-spectral (visible to near-IR) sensing. Here, a low cost infrared (IR) imaging camera is demonstrated with a commercially available digital single-lens reflex (DSLR) camera and an IR sensitive organic light emitting diode (IR-OLED). With an IR-OLED, IR images at a wavelength of 1.2 µm are directly converted to visible images which are then recorded in a Si-CMOS DSLR camera. This multi-spectral imaging system is capable of capturing images at wavelengths in the near-infrared as well as visible regions.

Recent advances with optical upconverters made from all-organic and hybrid materials

“…The intrinsic ɳ ph potential of that upconverter was not fully harnessed at that time because the absorption maximum of the sensitizing SnPc:C 60 layer is at 740 nm and a relatively small fraction of incident light at 830 nm was absorbed in the tail of the long wavelength absorption band [38]. Indeed, it was demonstrated later on that the peak photon conversion efficiency is at 740 nm and ɳ ph = 11.3% was measured at 12 V [27]. The device structure was at the same time improved by adding a hole blocking layer between ITO and the NIR sensitizer.…”

“…The PbSe upconverter showed sensitivity up to 1500 nm and a maximum at 1300 nm with ɳ ph = 1.3%, at an operating voltage of 17 V. The low value of ɳ ph was attributed to the small fraction of NIR light absorbed in the 50 nm thick PbSe film. Subsequently, a similar upconverter was fabricated by using PbS quantum dots as NIR sensitizing film with a peak sensitivity at 1200 nm [27]. This device was incorporated in a digital camera and an imaging system capable of NIR as well as visible imaging was realized.…”

“…A final processing challenge is that in an upconverter the top electrode should preferably be visibly transparent, in order that the emitted visible light can be detected at the opposite side of the incident NIR light. So far, semitransparent cathodes of upconverters were deposited as thin metal/dielectric layer via thermal evaporation [25][26][27]. However, several concepts for solution-processable transparent electrodes can be borrowed from related fields of research, such as spray-coating of metal nanowires or lamination of carbon nanotubes and graphene [55,56].…”

“…In addition to manufacturing benefits, organic and hybrid materials have the advantage over broadband absorbing inorganic semiconductors that their optical bandgap and absorption bandwidth can be tailored, to a greater or lesser extent. For the photodetector part in an upconverter, it is particularly desirable to have narrowband NIR-selective sensitive materials that do not absorb in the visible [4,[25][26][27][28]. Substantial progress is being made with individual organic and hybrid photodetectors, and lightemitting devices [3,4,[29][30][31] and it is anticipated that inspiration can be obtained from these standalone devices for the design and realization of improved upconverters.…”

Cathodic-controlled and near-infrared organic upconverter for local blood vessels mapping

“…In addition, the conversion efficiency exceeded 6% at 7 V and the image resolution achieved 400 dots per inch (dpi). Note that such an organic upconverter’s performance is the highest value reported to date68141519. To realize a new IR imaging device, in this paper we describe a 3.46% conversion efficiency, cathodic-controlled, and NIR organic upconverter for 3D mapping applications, where our proposed imaging system included several components, i.e.…”