Effect of pressure on crystal structure and charge transport properties of 2,6-diphenylanthracene
- PDF / 750,156 Bytes
- 14 Pages / 584.957 x 782.986 pts Page_size
- 51 Downloads / 187 Views
The influence of hydrostatic compression on the charge transport properties of an excellent 2,6-diphenylanthracene (2,6-DPA) semiconducting single crystal was investigated up to 10 GPa by performing density-functional calculations together with the tight binding approximation. In this pressure region the lattice constants a, b and c decrease by up to 0.948 Å (5.23%), 1.30 Å (17.26%), and 0.711 Å (11.34%), respectively, while the monoclinic angle b increases by 3.4°. The unit-cell volume decreases by increasing pressure, and the volume decreases by 30.5% at 10 GPa. In comparison, the C–C and C–H intermolecular distances within and between the herringbone layers reduced by 16–19% and 16–24%, respectively, in the same pressure ranges. The results indicate that under high pressure, the molecular planes of the crystal become more and more parallel to each other due to molecular rearrangement in the 2,6-DPA crystal. The band gap decreases with increasing pressure due to decreasing intermolecular separation between neighboring molecules. Finally, the results indicate an improvement of the hole mobility of 2,6-DPA single crystals under hydrostatic pressure.
I. INTRODUCTION
Since the recognition of semiconductor behavior of low molecular weight anthracene in 1963 by Pope,1 numerous researchers have been engaged in probing the potential organic semiconductor (OSCs) materials intended for the progress of next generation ultrathin organic field-effect transistors (OFETs).2 Charge carrier mobility (l) is an important factor which governs the performance of the OFETs. Normally, higher mobilities offer more potential for faster switching of OFETs. As a whole, the charge carrier mobility in OSCs critically depends on the molecular packing, disorder, size/molecular weight, charge density, electric field, temperature and pressure.3 Previous studies reported that the intermolecular separation between adjacent molecules in organic crystals is affected by both the electric field and hydrostatic pressure.3 On the other hand, within an organic crystal, the amount of orbital overlap and rate of charge transfer between adjacent molecules is governed by the intermolecular separation. In ultrapure single crystals, charge mobility is mostly independent of electric field at room temperature, whereas at low temperature, the mobility is seen to decrease with an increase in the electric field.3–10 Apart from experimental studies, a theoretical approach Contributing Editor: Erik G. Herbert a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2016.435
has recently been developed, which is useful to distinguish the influence of the external electric field on the charge transport parameters, such as, the transfer integrals (t) and the reorganization energy (k).11,12 Sancho-Garcia et al. have stated that the application of an external electric field in the range 106–108 V/cm along the long molecular axis of a pentacene molecule almost unaffected the inner k.11 Olivier et al. performed the Monte Carlo simulations and observe
Data Loading...
