A Hemispherical Image Sensor Array Fabricated with Organic Photomemory Transistors

Abstract

Hemispherical image sensors simplify lens designs, reduce optical aberrations, and improve image resolution for compact wide‐field‐of‐view cameras. To achieve hemispherical image sensors, organic materials are promising candidates due to the following advantages: tunability of optoelectronic/spectral response and low‐temperature low‐cost processes. Here, a photolithographic process is developed to prepare a hemispherical image sensor array using organic thin film photomemory transistors with a density of 308 pixels per square centimeter. This design includes only one photomemory transistor as a single active pixel, in contrast to the conventional pixel architecture, consisting of select/readout/reset transistors and a photodiode. The organic photomemory transistor, comprising light‐sensitive organic semiconductor and charge‐trapping dielectric, is able to achieve a linear photoresponse (light intensity range, from 1 to 50 W m−2), along with a responsivity as high as 1.6 A W−1 (wavelength = 465 nm) for a dark current of 0.24 A m−2 (drain voltage = −1.5 V). These observed values represent the best responsivity for similar dark currents among all the reported hemispherical image sensor arrays to date. A transfer method was further developed that does not damage organic materials for hemispherical organic photomemory transistor arrays. These developed techniques are scalable and are amenable for other high‐resolution 3D organic semiconductor devices.

Solution-Processed Organic–Inorganic Semiconductor Heterostructures for Advanced Hybrid Phototransistors

“…Aside from the high responsivity and intrinsic amplification of the three-terminal structure, the phototransistor also possesses low noise and no pixel crosstalk properties, which is of great benefit to the large-area image sensor matrix and monolithic integration with other electronic components. , Figure a depicts a circuit diagram illustrating a static phototransistor array for NIR light imaging applications, where each pixel consists of only one phototransistor with the global gate electrode. A phototransistor array (10 × 10) has been reported based on an organic/inorganic heterojunction (Figure b) with large-area process compatibility and uniformity (Figure c).…”

Advanced Bioinspired Organic Sensors for Future‐Oriented Intelligent Applications

“…Wide field of view High-resolution imaging Pentance Charge trapping [46] PDLLA-g-PAA/PEG a) Phase transition [58] Light vision P3HT:PCBM/PDPP3T:PCBM b) Photogenerated carriers Charge trapping [59] Color vision DNTT/C 10 -DNTT/BPE-PTCDI/PDI-sol Wavelength selectivity [60] Neuromorphic image processing sensors…”

“…The bionic sensors mainly focus on the five conventionally acknowledged senses (vision, touch, hearing, olfaction, and gustation) of living organisms and mimic their behaviors through the combination of functional materials, the design of device structures, and sensing physics. [46][47][48][49][50] In this section, several types of advanced organic sensory devices, including visual, tactile, and other artificial sensors are discussed.…”

“…A common method for fabricating curved image sensors is to prepare thin and deformable planar devices and then transfer and attach them to the target surface. [46,68,69] Wang et al reported the water-assisted glass strategy to prepare a conformal organic surface array to simulate retinal structures (Figure 2a). [68] The device consisted of an organic heterojunction-based photosensitive voltage divider and an organic electrochemical synapse, which were responsible for light perception and neural morphology readout, respectively.…”

Conformability of flexible sheets on spherical surfaces

“…However, today’s flexible displays are only able to form or conform to developable surfaces that have zero Gaussian curvatures and can fully unroll onto a plane. Thin-film electronics able to conform to three-dimensional (3D) curvilinear surfaces ( 1 ) can unleash much broader possibilities, particularly body-conformable electronics ( 2 ), surface-conformable antenna ( 3 ), conformal electronic armor ( 4 ), bioinspired electronic eyes ( 5 , 6 ), and so on. Well-known examples of body-conformable electronics include epidermal electronics intimately but noninvasively coupled to the skin ( 7 ), ultrathin electrocorticography (ECoG) electrodes accommodating brain curvature and movement ( 8 ), e-dura surrounding the spinal cord ( 9 ), glucose-sensing contact lenses ( 10 ) or artificial retina with a matching curvature to the eyeball ( 11 ), etc.…”