The role of defects in organic image sensors for green photodiode

Hybrid Organic-Si C-MOSFET Image Sensor Designed with Blue-, Green-, and Red-Sensitive Organic Photodiodes on Si C-MOSFET-Based Photo Signal Sensor Circuit

The resolution of Si complementary metal-oxide-semiconductor field-effect transistor (C-MOSFET) image sensors (CISs) has been intensively enhanced to follow the technological revolution of smartphones, AI devices, autonomous cars, robots, and drones, approaching the physical and material limits of a resolution increase in conventional Si CISs because of the low quantum efficiency (i.e., ~40%) and aperture ratio (i.e., ~60%). As a novel solution, a hybrid organic-Si image sensor was developed by implementing B, G, and R organic photodiodes on four n-MOSFETs for photocurrent sensing. Photosensitive organic donor and acceptor materials were designed with cost-effective small molecules, i.e., the B, G, and R donor and acceptor small molecules were Coumarin6 and C_60, DMQA and MePTC, and ZnPc and TiOPc, respectively. The output voltage sensing margins (i.e., photocurrent signal difference) of the hybrid organic-Si B, G, and R image sensor pixels presented results 17, 11, and 37% higher than those of conventional Si CISs. In addition, the hybrid organic-Si B, G, and R image sensor pixels could achieve an ideal aperture ratio (i.e., ~100%) compared with a Si CIS pixel using the backside illumination process (i.e., ~60%). Moreover, they may display a lower fabrication cost than image sensors because of the simple image sensor structure (i.e., hybrid organic-Si photodiode with four n-MOSFETs).

Menezes L, Tittl A, Ren H, Maier SA. Optical Metasurfaces for Energy Conversion

Nanostructured surfaces with designed optical functionalities, such as metasurfaces, allow efficient harvesting of light at the nanoscale, enhancing light-matter interactions for a wide variety of material combinations. Exploiting light-driven matter excitations in these artificial materials opens up a new dimension in the conversion and management of energy at the nanoscale. In this review, we outline the impact, opportunities, applications, and challenges of optical metasurfaces in converting the energy of incoming photons into frequency-shifted photons, phonons, and energetic charge carriers. A myriad of opportunities await for the utilization of the converted energy. Here we cover the most pertinent aspects from a fundamental nanoscopic viewpoint all the way to applications.

High-speed and high-precision PbSe/PbI2 solution process mid-infrared camera

Infrared (IR) cameras based on semiconductors grown by epitaxial methods face two main challenges, which are cost and operating at room temperature. The alternative new technologies which can tackle these two difficulties develop new and facile material and methods. Moreover, the implementation of high speed camera, which makes high resolution images with normal methods, is very expensive. In this paper, a new nanostructure based on a cost-effective solution processed technology for the implementation of the high-speed mid-infrared light camera at room temperature is proposed. To this end, the chemically synthesized PbSe-PbI2 core-shell Quantum Dots (QDs) are used. In this work, a camera including 10 × 10 pixels is fabricated and synthesized QDs spin-coated on interdigitated contact (IDC) and then the fabricated system passivated by epoxy resin. Finally, using an electronic reading circuit, all pixels are converted to an image on the monitor. To model the fabricated camera, we solved Schrodinger-Poisson equations self consistently. Then output current from each pixel is modeled based on semiconductor physics and dark and photocurrent, as well as Responsivity and Detectivity, are calculated. Then the fabricated device is examined, and dark and photocurrents are measured and compared to the theoretical results. The obtained results indicate that the obtained theoretical and measured experimental results are in good agreement together. The fabricated detector is high speed with a rise time of 100 ns. With this speed, we can get 10 million frames per second; this means we can get very high-resolution images. The speed of operation is examined experimentally using a chopper that modulates input light with 50, 100, 250, and 500 Hz. It is shown that the fabricated device operates well in these situations, and it is not limited by the speed of detector. Finally, for the demonstration of the proposed device operation, some pictures and movies taken by the camera are attached and inserted in the paper.

Molecular Engineering of a Donor-Acceptor Polymer To Realize Single Band Absorption toward a Red-Selective Thin-Film Organic Photodiode

Herein, we explore the strategy of realizing a red-selective thin-film organic photodiode (OPD) by synthesizing a new copolymer with a highly selective red-absorption feature. PCZ-Th-DPP, with phenanthrocarbazole (PCZ) and diketopyrrolopyrrole (DPP) as donor and acceptor units, respectively, was strategically designed/synthesized based on a time-dependent density functional theory calculation, which predicted the significant suppression of the band II absorption of PCZ-Th-DPP due to the extremely efficient intramolecular charge transfer. We demonstrate that the synthesized PCZ-Th-DPP exhibits not only a high absorption coefficient within the red-selective band I region, as theoretically predicted, but also a preferential face-on intermolecular structure in the thin-film state, which is beneficial for vertical charge extraction as an outcome of a glancing incidence X-ray diffraction study. By employing PCZ-Th-DPP as a photoactive layer of Schottky OPD, to fully match its absorption characteristic to the spectral response of the red-selective OPD, we demonstrate a genuine red-selective specific detectivity in the order of 10¹² Jones while maintaining a thin active layer thickness of ∼300 nm. This work demonstrates the possibility of realizing a full color image sensor with a synthetic approach to the constituting active layers without optical manipulation.