Critical Factors of Diarylethene for a High-Performance Photoprogrammable Polymer Transistor: Crystallographic Compatibility, Quantum Yield, and Fatigue Resistance

Abstract

We show that crystallographic compatibility, quantum yield, and fatigue resistance are three important factors that diarylethene (DAE) should simultaneously satisfy to realize high-performance photoprogrammable polymer field-effect transistors (FETs). The enhancement of crystallographic compatibility achieved by locating DAE preferentially in the vicinity of intercrystallite tie chains is mainly dependent on the overall molecular volume of DAE. The quantum yield of DAE for photocyclization is dependent on the molar portion of the photoactive antiparallel conformer, while photocycloreversion is determined by both the aromatic stabilization energy of the closed isomer and allowed free space for each DAE molecule. While the chemical resistance of DAE relies entirely on its chemical structure, the electrical fatigue resistance of DAE-embedded FET depends on both the morphological/structural environment of the DAE/polymer blend and chemical resistance of the DAE molecule. To precisely control each of these determining factors of DAE-embedded polymer FETs, a series of DAE is synthesized and systematically analyzed. High-mobility DPPDTT is blended with various DAE derivatives as a matrix polymer. We show that strategic substitution of functional groups at the specific reaction site of DAE can lead to an ideal molecular switch for high-performance photoprogrammable polymer FETs with high photoprogrammable switching ratios of 4405, as well as high electrical fatigue resistance of up to 100 photoprogrammable switching steps. The physics behind the success of the optimized DAE structure is discussed using the results from various analysis techniques. We shed light on how the crystallographic compatibility, quantum yield, and fatigue resistance of DAE can vary with and be optimized by chemical modification of the DAE reaction site.

Molecular‐Switch‐Embedded Solution‐Processed Semiconductors

“…The closed‐ring isomer of D1a has an adequate HOMO level for trapping holes of several p‐type polymeric OSCs. [ 114 ] To yield high photoprogrammable fatigue resistance and photoprogrammable switching ratio, five different DAE (D1)—D1a, D1b, D1c, D1d, and D1e—were synthesized and studied using well‐known high mobility p‐type polymer DPPT‐TT. All DAE were functionalized with only alkyl substituents so that energy level was unaltered.…”

“…The energy of the conduction band minimum (CBM) of WSe 2 was located between that Reproduced with permission. [114] Copyright 2021, American Chemical Society.…”

“…Photoprogrammed switching performance of DPPDTT/DAE FET devices: C) transfer curves of DPPT-TT/D1e-based FETs for alternate cycles of UV (312 nm) and visible light (520 nm) light irradiation for up to 10 steps and D) photoprogrammed reversible switching behavior of the DPPT-TT/D1e-based FETs after irradiation with UV (312 nm) and visible light (520 nm) of up to 100 steps. The UV light irradiation time is 30 s, and the visible light irradiation time is 300 s. All single points of the I DS values are extracted from the transfer curves at V G = −30 V and V DS = −30 V. E) Histogram of photoprogrammed switching of hole mobility of DPPT-TT and DPPT-TT/DAE blended FETs before and after UV light irradiation for the first cycle of the transfer curve.Reproduced with permission [114]. Copyright 2021, American Chemical Society.…”

Boosting photoprogramming performance of molecular-switch-embedded organic transistors via structural optimization of polymer semiconductors

“…[15][16][17][18][19][20][21] This approach has a significant advantage in terms of imparting structural simplicity over strategies involving the use of other organic memory devices such as floating-gate-or electret-based OFETs, because only the channel layer is slightly tuned from a single-component organic semiconductor to an organic semiconductor/molecular switch mixture, while all other constituting layers of OFETs can be the same. [22][23][24][25][26][27] This advantage has led many researchers to attempt to realize high-performance photoprogrammable OFETs with various combinations of organic semiconductors and molecular switches. For example, Samori et al reported photoprogrammable OFETs employing several organic semiconductors mixed with cyclopentene-based DAE derivatives, resulting in outstanding photoprogrammable I DS ON/OFF ratios of over 10 2 (the photoprogrammable I DS ON/OFF ratio is defined as |I DS (DAE_o)|/|I DS (DAE_c)|).…”

“…For example, Samori et al reported photoprogrammable OFETs employing several organic semiconductors mixed with cyclopentene-based DAE derivatives, resulting in outstanding photoprogrammable I DS ON/OFF ratios of over 10 2 (the photoprogrammable I DS ON/OFF ratio is defined as |I DS (DAE_o)|/|I DS (DAE_c)|). [22][23][24][25][26][27][28][29] There have also been reports on optimizing the chemical structures of DAEs to further enhance the photoprogrammable I DS ON/OFF ratios. 27 One notable point from these previous studies illustrates that typical diketopyrrolopyrrole (DPP)-based copolymers, which are known to have high charge carrier mobilities, are not suitable in terms of photoprogramming stability for most DAEs due to their excessively high crystalline nature.…”