*3.3.5 7,14-Bis((trimethylsilyl)ethynyl)-dibenzo[b,def ]-chrysene*

Stevens et al. found two polymorphs of 7,14-bis((trimethylsilyl)ethynyl) dibenzo[b,def]-chrysene (TMS-DBC) using the physical vapor transport technology [58]. The first polymorph was obtained as red needles at low temperature, which was named as LT-phase (**Figure 7a**). The second polymorph was formed at high temperature as yellow plates and named HT-phase (**Figure 7b**). Further investigations found that the LT-phase can also be fabricated from solution and could not be converted into HT-phase by thermal annealing. Single-crystal OFETs of the two polymorphs were fabricated. The results revealed that the hole mobility of the HT-phase is up to 2.1 cm2 V<sup>−</sup><sup>1</sup> s<sup>−</sup><sup>1</sup> , while that of the LT-phase is only 0.028 cm2 V<sup>−</sup><sup>1</sup> s<sup>−</sup><sup>1</sup> .

As shown in **Figure 7**, the LT-phase adopts one-dimensional (1D) slipped stacking, while the HT-phase exhibits two-dimensional (2D) brick-wall stacking. Quantum chemical calculations revealed that the LT-phase possesses 1D charge transport channel along the π-stacking direction with a transfer integral of −86.8 × 10<sup>−</sup><sup>3</sup> eV (**Figure 7b**). In contrast, the HT-phase possesses exhibits 2D charge transfer channels with transfer integrals of −77.3 × 10<sup>−</sup><sup>3</sup> and − 41 × 10<sup>−</sup><sup>3</sup> eV along the t1 and t2 directions, respectively (**Figure 7e**). Though the HT-phase exhibits slightly smaller transfer integral (absolute value) than that of the LT-phase, its 2D charge transport channels benefit charge transfer, which allows charge carriers to take alternative pathways around defects or trap states. As a result, the HT-phase facilitates higher mobility than the LT-phase.
