Organic field-effect transistors have been envisioned for advanced photodetectors because the organic semiconductors provide unique absorption characteristics, low-cost fabrication, or compatibility with flexible substrates. However, the response time of organic phototransistors still does not reach the required application level. Here, we report the photoresponse of copper phthalocyanine phototransistor in a steady state and under pulsed illumination. The detailed analysis based on the random walk among a field of traps was used to evaluate the dimensionality of electron transport in a device.

Neuromorphic computing systems require artificial synaptic devices capable of emulating complex biological neural functions. This study presents a dinaphtho[2,3‐b:2′,3′‐f]thieno[3,2‐b]thiophene (DNTT)‐based organic field‐effect transistor that demonstrates synaptic plasticity under optical stimulation at 200 K. The device exhibits a dual‐mechanism synaptic behavior through charge separation and trapping, where photogenerated holes provide rapid transport while electrons are preferentially captured in deep trap states, creating persistent field modulation. Excitatory postsynaptic current measurements reveal characteristic three‐phase temporal dynamics with rapid activation, exponential decay, and sustained enhancement lasting tens of minutes. Paired‐pulse facilitation demonstrates short‐term plasticity with dual exponential decay constants of 140 and 610 ms, while multi‐pulse stimulation produces remarkable persistent current level enhancement exceeding 10 000% of the initial baseline, reflecting sequential filling of continuous trap state distributions. The device simultaneously implements both short‐term and long‐term plasticity mechanisms in a single component, enabling simultaneous working memory and persistent information storage functions. Neuromorphic functionality is demonstrated through simulated XOR logic operations, showing non‐linearly separable computation capabilities. The 200 K operating temperature aligns favorably with Mars surface conditions, requiring minimal heating compared to terrestrial cooling requirements, making the device particularly promising for space‐based neuromorphic systems where radiation‐hard organic semiconductors provide additional advantages.

SPIE Digital Library Proceedings

Organic thin-film transistors based on dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT) are attractive for low-cost, large-area electronics, but in unencapsulated devices, atmospheric oxidation generates charge traps whose electronic character—which product traps holes and which traps electrons—has not been mapped systematically. Here, 39 oxygen- and hydroxyl-related defect identities of DNTT are screened with the semi-empirical GFN2-xTB method, complemented by an a priori frontier reactivity index, and classified by the sign of the frontier-level shift. This sign obeys a simple rule: a net $\pi$-donating hydroxyl raises the HOMO and yields a hole trap, whereas a net $\pi$-accepting carbonyl or quinone lowers the frontier levels and yields a deep electron trap. Hybrid density-functional theory (B3LYP/def2-TZVP) confirms the sign rule and the ordering of the shifts across all closed-shell defect classes. The rule provides a compact, defect-level rationalisation of the well-known asymmetry whereby p-type acenes tolerate air far better than n-type ones. Finally, a hole trap of about 0.255 eV, measured by deep-level transient Fourier spectroscopy, is shown to be consistent with a hydroxyl-related origin, without claiming a unique microscopic assignment.