Hybrid image sensor of small molecule organic photodiode on CMOS – Integration and characterization

Abstract

Organic photodiodes (OPDs) for its interesting optoelectronic properties has the potential to be utilized with complementary metal-oxide-semiconductor (CMOS) circuit for imaging, automotive, and security based applications. To achieve such a hybrid device as an image sensor, it is imperative that the quality of the OPD remains high on the CMOS substrate and that it has a well-connected optoelectronic interface with the underneath readout integrated circuit (ROIC) for efficient photogeneration and signal readout. Here, we demonstrate seamless integration of a thermally deposited visible light sensitive small molecule OPD on a standard commercial CMOS substrate using optimized doped PCBM buffer layer. Under a standard power supply voltage of 3 V, this hybrid device shows an excellent photolinearity in the entire bias regime, a high pixel sensitivity of 2 V/Lux.sec, a dynamic range (DR) of 71 dB, and a low dark leakage current density of 1 nA/cm2. Moreover, the integrated OPD has a minimum bandwidth of 400 kHz. The photoresponse nonuniformity being only 1.7%, achieved under research lab conditions, strengthens the notion that this fully-CMOS compatible technology has the potential to be applied in high-performance large-scale imaging array.

Narrowband organic photodetectors – towards miniaturized, spectroscopic sensing

“…This can be done either by integrating OPDs with state-of-art CMOS technology or building completely organic based imagers, which is more challenging, as also organic transistors are required. Although some examples are found in the literature in that direction, 1,[170][171][172][173] further research is needed.…”

Top‐Illuminated Organic Photodetectors beyond 1000 nm Wavelength Response Enabled by a Well‐Defined Interfacial Engineering

“…[1,15,24,25] It is worth worrying about the true performance of the top-illuminated device architecture (substrate/metal/HBL/PAL/HTL/top transparent electrode, illuminated from top electrode side) when building an OPD onto the contact metal of the bottom ROIC. [4,6] The schematic diagram is shown in Figure S1 (Supporting Information). To expedite the industrialization of organic imager technology, device engineering and process integration for top-illuminated devices must be well considered to minimize the performance loss.…”

“…To date, only a few research teams have addressed the challenges associated with device engineering issues for organic imager manufacturing. [1,[3][4][5][6]24] The performance of top-illuminated OPDs is still mainly limited by interface engineering and device architecture, including the selection of appropriate solution-processable interlayers and deposition of transparent top electrodes. In this paper, we present a well-defined device architecture to demonstrate solutionprocessable, top-illuminated OPDs.…”

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OPD and readout integrated circuit (ROIC) enables several advantages. [6] For example, the sensor area can potentially reach a larger fill factor as the OPD is directly overlaid on top of an ROIC, which means that more incident photons will be absorbed by the photoactive layer (PAL), leading to imagers that are more sensitive to light. [5] In addition, the response spectra for organic semiconductors can be designed and tuned by adjusting the chemical structure, and the application of organic-based image sensors can be easily extended by changing the PAL materials with various light responses.

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Recent Advances in Solution‐Processable Organic Photodetectors and Applications in Flexible Electronics

“…Schematic diagrams of a) OPDs integrated on the top of a CMOS backplane, b) OPDs integrated on the top of an a-Si TFT ROIC, c) an imaging passive pixel sensor circuit comprising an OPD and a top-contact OTFT, d) an image pixel comprising a PBDTTT-C-T:PC 71 BM OPD and a top-contact OTFT. (a) Reproduced under terms of the CC-BY license [168]. Copyright 2020, The Authors.…”