Fast Photoresponsive Phototransistor Memory Using Star-Shaped Conjugated Rod–Coil Molecules as a Floating Gate

Abstract

With the explosive growth in data generation, photomemory capable of multibit data storage is highly desired to enhance the capacity of storage media. To improve the performance of phototransistor memory, an organic-molecule-based electret with an elaborate nanostructure is of great importance because it can enable multibit data storage in a memory device with high stability. In this study, a series of star-shaped rod–coil molecules consisting of perylenediimide (PDI) and biobased solanesol were synthesized in two-armed (PDI-Sol2), four-armed (PDI-Sol4), and six-armed (PDI-Sol6) architectures. Their molecular architecture–morphology relationships were investigated, and phototransistor memory was fabricated and characterized to evaluate the structure–performance relationship of these rod–coil molecules. Accordingly, the memory devices were enabled by photowriting with panchromatic light (405–650 nm) and electrical erasing using a gate bias. The PDI-Sol4-based memory device showed high memory ratios of 10 000 over 10 000 s and a rapid multilevel photoresponse of 50 ms. This achievement is related to the favorable energy-level alignment, isolated nanostructure, and face-on orientation of PDI-Sol4, which eliminated the charge tunneling barrier. The results of this study provide a new strategy for tailoring nanostructures in organic-molecule-based electrets by using a star-shaped rod–coil architecture for high-performance phototransistor memory.

Flexibly Photo-Regulated Brain-Inspired Functions in Flexible Neuromorphic Transistors

“…Consequently, it is desirable to devise a three-terminal platform with the real-time signal monitoring and regulation and the smooth memristive responses. To date, the organic transistor memory has spawned numerous studies, − part of which concerns the effective, flexible role of light input in modulating the device properties, including enhancement of charge storage, enlargement of the memory window, and improvement in the response rate. − In charging-based organic transistor devices, the floating gates referring to charge trapping medium mainly include discrete nano-floating gates (e.g., metal nanoparticles, quantum dots, ion-gel membrane, rod–coil molecules, and 2D materials) and continuous polymer electrets. − Besides, rechargeable polymer electrets with low-temperature and large-area solution processability have significant advantages over morphology-dependent nano-floating gates for flexible synaptic transistors.…”

Discotic Liquid Crystals with Highly Ordered Columnar Hexagonal Structure for Ultraviolet Light-Sensitive Phototransistor Memory

“…Notably, the conjugated rod−coil molecule with a 4armed architecture induced a face-on orientation, which led to a faster and 2 times higher photoresponse to multiple light pulses (50 ms) than that with a 2-armed architecture. As a result, the corresponding phototransistor memory comprising the conjugated rod−coil molecule with star-shaped side-chains was able to achieve a high memory ratio of 10 4 over 10 4 s. 37,38 It is worth noting that liquid crystalline molecules with an intrinsically self-assembled layer structure (calamitic-type liquid crystals) or nanoarray (discotic-type liquid crystals) have attracted tremendous research interest in high-performance photomemory. 39 Recently, the utilization of calamitic liquid crystals in forming an ordered layer structure associated with an end-on orientation to sufficiently block the trapped charge in the electret has been extensively studied.…”

Stretchable π-conjugated polymer electrets for mechanoelectric generators

“…Compared to the electronically inactive polymers described above, π-conjugated molecules and polymers are expected to trap charges with greater thermodynamic stability because they easily ionize [14]. By taking advantage of this feature, several πelectrets, including perylene diimides [15], phthalocyanines [16,17], and π-conjugated polymers [18][19][20], have been designed for organic field effect transistor (OFET) memories. However, π-electrets exhibit relatively high electrical conductivity, resulting in a short lifetime for trapped charges due to self-discharge, and thus are considered unsuitable for MEGs [21].…”