Sang Kyu Park

2D organic semiconductor crystals are emerging as a fascinating platform with regard to their applications in organic field-effect transistors (OFETs), attributed to their enhanced charge transport efficiency and their new optoelectronic functions, based on their unique morphological features. Advances in material processing techniques have not only enabled easy fabrication of few-monolayered 2D nanostructures but also facilitated exploration of the interesting properties induced by characterist

An efficient bulk heterojunction all-small-molecule organic solar cell composed of a high-performance small-molecule donor and a self-assembling nonfullerene acceptor is demonstrated. Favorable nanoscale phase separation and enhanced charge carrier generation with transport in this donor–acceptor system assures a maximum power conversion efficiency of 5.4%.

A well-organized donor–acceptor crystalline structure is examined for high ­performance nonfullerene solar cells. By thermal annealing, nanoscale structures of both donor and acceptor domains are successfully modulated, followed by ­significant changes in the resulting ­photovoltaic characteristics. When annealed at 90 °C, a maximum power conversion efficiency of 7.64% with a ­remarkable open-circuit voltage of 1.03 V is obtained. As a service to our authors and readers, this journal provides su

Molecular martensitic materials are an emerging class of smart materials with enormous tunability in physicochemical properties, attributed to the tailored molecular and crystal structures through molecular design. This class of materials exhibits ultrafast and reversible structural transitions in response to thermal and mechanical stimuli, which underlies fascinating properties such as thermoelasticity, superelasticity, ferroelasticity, and shape memory effect. These dynamic properties are not

Abstract A new high‐performing small molecule n‐channel semiconductor based on diketopyrrolopyrrole (DPP), 2,2′‐(5,5′‐(2,5‐bis(2‐ethylhexyl)‐3,6‐dioxo‐2,3,5,6‐tetrahydropyrrolo[3,4‐c]pyrrole‐1,4‐diyl)bis(thiophene‐5,2‐diyl))bis(methan‐1‐yl‐1‐ylidene)dimalononitrile (DPP‐T‐DCV), is successfully synthesized. The frontier molecular orbitals in this designed structure are elaborately tuned by introducing a strong electron‐accepting functionality (dicyanovinyl). The well‐defined lamellar structures o

Abstract Like silicon, single crystals of organic semiconductors are pursued to attain intrinsic charge transport properties. However, they are intolerant to mechanical deformation, impeding their application in flexible electronic devices. Such contradictory properties, namely exceptional molecular ordering and mechanical flexibility, are unified in this work. We found that bis(triisopropylsilylethynyl)pentacene (TIPS‐P) crystals can undergo mechanically induced structural transitions to exhibi

We present a developed highly balanced and thermally stable ambipolar semiconducting polymer PBCDC consisting of diketopyrrolo[3,4- c ]pyrrole and benzo[1,2- b:4,5- b ′]dithiophene building blocks connected by a cyanovinylene linker unit. Stabilization of the frontier molecular orbitals and delocalization of the LUMO on the whole structural unit were realized by introducing the strong electron-withdrawing cyanovinylene linker. In addition to such electronic effects, the molecular stacking and cr

Abstract A pure red‐emitting organic light‐emitting transistor (OLET) is successfully fabricated using a π‐extended dicyanodistyrylbenzene‐type organic semiconductor material (Hex‐4‐TFPTA), which shows outstanding charge transport and solid‐state luminescence at the same time. Based on the structural (X‐ray) and photophysical analyses, it is found that the appropriate molecular stacking and highly allowed S 1 →S 0 transition of Hex‐4‐TFPTA created the ambidextrous balance between electrical mobi

<italic>Via</italic>the cooperative effects of intramolecular charge transfer interactions and extension of conjugation, low-band gap organic semiconductors have successfully been prepared.

Abstract Like silicon, single crystals of organic semiconductors are pursued to attain intrinsic charge transport properties. However, they are intolerant to mechanical deformation, impeding their application in flexible electronic devices. Such contradictory properties, namely exceptional molecular ordering and mechanical flexibility, are unified in this work. We found that bis(triisopropylsilylethynyl)pentacene (TIPS‐P) crystals can undergo mechanically induced structural transitions to exhibi

Doping of conjugated polymers (CPs) is a promising strategy to obtain solution‐processable and highly conductive films; however, the improvement in electrical conductivity is limited owing to the relatively poor carrier mobility of CPs. Herein, a CP with excellent molecular doping ability, i.e., poly[2‐([2,2'‐bithiophen]‐5‐yl)‐3,8‐difluoro‐5,10‐bis(5‐octylpentadecyl)‐5,10‐dihydroindolo[3,2‐b]indole] ( PIDF‐BT ) is wrapped onto the surface of single‐walled carbon nanotubes (SWCNTs). The resulting

Ferroelasticity of organic single crystals has recently attracted great research interest. It is a reversible twinning transition in response to mechanical stress that imparts remarkable deformability to crystalline materials while allowing materials to retain their inherent functional properties. These appealing attributes of ferroelasticity promise high-performance ultraflexible, stretchable single-crystalline (opto-) electronics. In this work, we unravel structural criteria for ferroelastic t

Abstract Molecular crystals capable of colossal thermal expansion (TE) are fascinating owing to their substantial and continuous volume changes and reasonably linear responses to temperature. This makes them promising candidates for micromachine applications. Macroscopic motion is driven by subtle yet cooperative movements of molecules that respond to the thermal motions of dynamic functional units. The study of p‐TIPS‐DSB presented here offers a compelling case highlighting the relationship bet