High charge-carrier mobility and low trap density in a rubrene derivative

Abstract

We have synthesized, crystallized and studied the structural and electric transport properties of organic molecular crystals based on a rubrene derivative with t-butyl sidegroups at the 5,11 positions. Two crystalline modifications are observed: one (A) distinct from that of rubrene with larger spacings between the naphtacene backbones, the other (B) with a in-plane structure presumably very similar compared to rubrene. The electric transport properties reflect the different structures: in the latter phase (B) the in-plane hole mobility of 12 cm 2 /Vs measured on single crystal FETs is just as high as in rubrene crystals, while in the A phase no field-effect could be measured. The high crystal quality, studied in detail for B, reflects itself in the density of gap states: The deep-level trap density as low as 10 15 cm −3 eV −1 has been measured, and an exponential band tail with a characteristic energy of 22 meV is observed. The bulk mobility perpendicular to the molecular planes is estimated to be of order of 10 −3 -10 −1 cm 2 /Vs.

Rubrene: The Interplay between Intramolecular and Intermolecular Interactions Determines the Planarization of Its Tetracene Core in the Solid State

“…DFT analyses of the neutral ground states were carried out using a variety of density functionals containing empirically parameterized dispersion interactions that were found to perform well in a previous benchmark study: 28 B3LYP and B3LYP-D, [23][24][25] IP-tuned ωB97 and ωB97-D, 29 Tables S1 and S2 in the SI). All geometry optimizations were performed with the cc-pVDZ basis set.…”

“…21,[24][25][26] Examples of this conformational variation are shown in Figure 1 where crystals of 1, 3, and 5 have planar tetracene cores, while in crystals of 2 and 4 the tetracene 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 5 backbones substantially twist. Rubrene derivatives that maintain planar tetracene backbones can have intermolecular electronic couplings that even surpass that of the parent compound 1 (though their charge-carrier mobilities in single-crystal field-effect transistors currently remain below those for 1).…”

Capturing the Role of Temperature and Entropy in Crystal Polymorphs Through Molecular Simulations

“…The material 7,14-bis((trimethylsilyl)ethynyl)dibenzo[b,def ]-chrysene (TMS-DBC) was recently shown to have a 75x larger hole mobility when adopting a 2D brickwork configuration rather than a 1D slipped stack configuration [29]. Similar examples of improved charge transport when adopting a new crystal structure have been observed in Rubrene [26], TIPS-pentacene [27], and C8-BTBT [28].…”

“…Properties than can change between polymorphs include density [11,20,31], compressibility [32], hardness [33,34], gel strength [35], flexibility [36], conductivity [26][27][28][29][30][37][38][39], explosivity [20,[22][23][24], catalytic activity [40,41], transparency [42,43], weather resistance [25,44], heat capacity [20], melting point [32,45,46], vapor pressure [46], stability [25,29], solubility [14,[47][48][49], bioavailability [14,33,48,[50][51][52][53][54], and dissolution rate [47,55,56].…”

“…Many commercial products such as drugs [14][15][16][17][18][19], explosives [20][21][22][23][24], dyes [25], and electrochemical materials [26][27][28][29][30] involve crystallized organic molecules with multiple solid forms.…”