Qin Tang

Soluble and Stable N‐Heteropentacenes with High Field‐Effect Mobility

Organic thin-fi lm transistors (OTFTs) are essential building blocks of large-area, fl exible, and low-cost organic electronics and offer promising applications in technology areas, such as light-weight and fl exible displays; radio-frequency identifi cation (RFID) circuitry; [ 1 ] and physical, chemical, and biological sensors. [ 2 ] The ultimate success of OTFTs requires developing organic semiconductors that allow 1) effi cient charge transport, which is characterized by high fi eld-effect mobility; 2) solution-based processing for low-cost fabrication; and 3) good operational stability of devices under ambient air, moisture, and light exposure. [ 3 ] Although the fi eld-effect mobilities of leading organic semiconductors in OTFTs have reached or even exceeded the value of amorphous silicon ( ≈ 1 cm 2 V − 1 s − 1 ), organic semiconductors that can meet all the above requirements are still rare. [ 4 ] Such challenge is particularly true for n-type (electron-transporting) organic semiconductors. [ 5 ] In fact the development of n-type organic semiconductors for OTFTs has lagged behind that of p-type ones, primarily due to the inherent instability of organic anions in the presence of air and water and problems with oxygen trapping within these materials. [ 4a ]

The Position of Nitrogen in N‐Heteropentacenes Matters

An exploratory study on novel silylethynylated N-heteropentacenes, which have their N atoms on the terminal rings of the pentacene backbone, is reported. This study leads to both p- and n-channel organic thin-film transistors with high field-effect mobility and also reveals that the position of the N atoms plays an important role in tuning the structures and properties of organic semiconductors based on N-heteropentacenes.

Induced Crystallization of Rubrene in Thin-Film Transistors

Rubrene (shown in Figure 1a ) holds the record for the highest fi eld effect mobility of organic semiconductors (15 to 40 cm 2 / V ⋅ s) as measured from the single crystal transistors. [ 1 , 2 ] However it has been found diffi cult to achieve high charge carrier mobility in thin fi lm transistors of rubrene because of the poor crystallinity of rubrene in conventional thin fi lms. [ 3 , 4 ] This has become an obstacle limiting practical applications of rubrene in organic electronics. In order to fabricate polycrystalline fi lms of rubrene, one elegant approach is annealing a hypereutetic mixture of rubrene and 9,10-diphenylanthracene. [ 5 ] Besides this solution processing method, several special techniques associated with vapor phase deposition, such as “hot wall” deposition, [ 6 ]

Hydrogen-Bonded Dihydrotetraazapentacenes

Three new members of N-heteropentacenes explored herein have adjacent pyrazine and dihydropyrazine rings at one end of the pentacene backbone. Interesting findings from this study include self-complementary N-H···N H-bonds in the solid state, solvent-dependent UV-vis absorption caused by H-bonding, and new p-type organic semiconductors with field effect mobility up to 0.7 cm(2) V(-1) s(-1).

Benzenoid and Quinonoid Nitrogen‐Containing Heteropentacenes

Benzenoid or quinonoid-that is the question? In connection with the debate on the structure of dihydro-5,7,12,14-tetraazapentacene, both benzenoid and quinonoid nitrogen-containing heteropentacenes were successfully isolated and investigated (see picture). This report presents an exploratory study of the molecular and electronic structures, molecular packing, and semiconductor properties of the two compounds. These findings may lead to useful implications for the interesting ladder polymers.

Unexpected Photooxidation of H-Bonded Tetracene

In our attempts of tuning the molecular packing of tetracene with H-bonding, we found that tetracenediamide was much more vulnerable to photooxidation than tetracene in crystals despite their similar sensitivity to photooxidation in solution. Unexpectedly photooxidation of tetracenediamide in solution and in crystals show different regioselectivities. To explain the regioselectivity, a mechanism involving H-bonding is proposed. This study indicates that molecular packing in solid state can play an important role in solid-gas reactions.

Revisiting zethrene: synthesis, reactivity and semiconductor properties

Zethrene, a unique polycyclic aromatic hydrocarbon with formally fixed C–C double bonds, is predicted to have interesting properties and potential applications as an optical and electronic material. Here we report a novel synthesis of zethrene with improved yield, which presumably involves dinaphtho[10]-annulene as an unstable intermediate. With this convenient access to zethrene, we used zethrene as a p-type semiconductor in thin film transistors for the first time. It is found that Diels–Alder addition to the bay region of zethrene leads to new derivatives of benzo[pqr]naphtho[8,1,2-bcd]perylene, which behave as n-type organic semiconductors.

Transistors from a conjugated macrocycle molecule : field and photo effects†

This study explores a conjugated macrocycle molecule and details its synthesis, molecular structure, assemblies in the solid state and application in phototransistors.