Search for: All records

This work resolves the inter- and intramolecular polarized absorption of polarons in the organic semiconductor P3HT, allowing previous theoretical predictions to be tested. Vibronic coupling is shown to be crucial in understanding polaron absorption. 

Abstract π‐conjugated polymers (CPs) that are concurrently soft and stretchable are needed for deformable electronics. Molecular‐level modification of indacenodithiophene (IDT) copolymers, a class of CPs that exhibit high hole mobilities (_hole), is an approach that can help realize intrinsically soft and stretchable CPs. Numerous examples of design strategies to adjust the stretchability of CPs exist, but imparting softness is comparatively less studied. In this study, a systematic molecular weight (MW) series is constructed on a promising candidate for soft CPs, poly(indacenodithiophene‐co‐thienopyrroledione) (p(IDT_C16‐TPD_C8)), by optimizing direct arylation polymerization conditions in hopes of improving stretchability andμ_holewithout significantly impacting softness. We found p(IDT_C16‐TPD_C8) at a degree of polymerization of 32 shows high stretchability (crack onset strain,CoS> 100%) without significantly impacting softness (elastic modulus,E= 32 MPa), which to the best of our knowledge outperforms previously reported stretchable and soft CPs. To further study how molecular‐level modifications impact polymer properties, a MW series of a new extended donor unit polymer, poly(indacenodithienothiophene‐co‐thienopyrroledione) (p(IDTT_C16‐TPD_C8)), was synthesized. The IDTT_C16copolymers did not result in a greater averageμ_holewhen comparing between p(IDTT_C16‐TPD_C8) and p(IDT_C16‐TPD_C8) despite their higher crystallinity observed by GIWAXS. While these findings warrant further investigation, this study points toward unique charge transport properties of IDT‐based polymers. 

Abstract Organic electrochemical transistors (OECTs) have shown promise as transducers and amplifiers of minute electronic potentials due to their large transconductances. Tuning the OECT threshold voltage is important to achieve low‐powered devices with amplification properties within the desired operational voltage range. However, traditional design approaches have struggled to decouple channel and materials properties from threshold voltage, thereby compromising on several other OECT performance metrics, such as electrochemical stability, transconductance, and dynamic range. In this work, simple solution‐processing methods are utilized to chemically dope polymer gate electrodes, thereby controlling their work function, which in turn tunes the operation voltage range of the OECTs without perturbing their channel properties. Chemical doping of initially air‐sensitive polymer electrodes further improves their electrochemical stability in ambient conditions. Thus, OECTs that are simultaneously low‐powered and electrochemically resistant to oxidative side reactions under ambient conditions are demonstrated. This approach shows that threshold voltage, which is once interwoven with other OECT properties, can in fact be an independent design parameter, expanding the design space of OECTs. 

Abstract In organic mixed ionic–electronic conductors (OMIECs), it is critical to understand the motion of ions in the electrolyte and OMIEC. Generally, the focus is on the movement of net charge during gating, and the motion of neutral anion–cation pairs is seldom considered. Uptake of mobile ion pairs by the semiconductor before electrochemical gating (passive uptake) can be advantageous as this can improve device speed, and both ions can participate in charge compensation during gating. Here, such passive ion pair uptake in high‐speed solid‐state devices is demonstrated using an ion gel electrolyte. This is compared to a polymerized ionic liquid (PIL) electrolyte to understand how ion pair uptake affects device characteristics. Using X‐ray photoelectron spectroscopy, the passive uptake of ion pairs from the ion gel into the OMIEC is detected, whereas no uptake is observed with a PIL electrolyte. This is corroborated by X‐ray scattering, which reveals morphological changes to the OMIEC from the uptake of ion pairs. With in situ Raman, a reorganization of both anions and cations is then observed during gating. Finally, the speed and retention of OMIEC‐based neuromorphic devices are tuned by controlling the freedom of charge motion in the electrolyte.