Pentacene

F₂-TES ADT was synthesized as described previously68 (link). PC₇₁BM, tetracene, rubrene, TIPS-pentacene and pentacene were purchased from Sigma Aldrich. F₂-TES ADT and TIPS-pentacene thin film samples were spin-cast (15 mg ml⁻¹, toluene) on polyimide precoated fused-silica substrates (the polyimide aids wetting of the organic semiconductor). For F₂-TES ADT: PC₇₁BM thin film samples, 4:1F₂-TES ADT:PC₇₁BM blend solutions (15 mg ml⁻¹ total material, mesitylene) were spin-cast on polyimide precoated fused-silica substrates. Samples were dried on a hot-plate at 50 °C for 10 min. Tetracene, rubrene and pentacene thin-film samples were prepared via thermal evaporation at a base pressure of <6 × 10⁻⁶ mbar.
Single crystals of F₂-ADT were grown through a physical vapour growth method. Details of the relevant method can be seen elsewhere69 . We used a growth apparatus equipped with source and growth heaters that were placed side-by-side. Temperatures of the heaters were regulated in such a way that high-quality single crystals could be produced. In the present studies we set the source and growth heaters at 240 °C and 220 °C, respectively. The growth duration was 6 h.

Pentacene (purity 99%, purchased from Sigma-Aldrich) is deposited from a homemade Knudsen cell evaporator at a deposition rate of one monolayer per 30 min. The overall preparation time of the sample including annealing and sputtering cycles of the metal substrate is about 3.5 h. Before conducting the photoemission experiment the film thickness and quality were verified by low-energy electron diffraction (LEED), evidencing the Pentacene bilayer structure on Ag(110)^{12 (link)} (see supplement, Fig. 1(a)). The sample is kept at room temperature during the deposition and experiment. The base pressure in the analyzer chamber is ∼1·10⁻¹⁰ mbar.

BaP (purity > 99%), fluoranthene (99%), pentacene (>99%), and pyrene (>99%) were purchased from Sigma (Sigma-Aldrich, St. Louis, MO, USA). Stock PAHs solutions were made in dimethyl sulfoxide (DMSO) (Sigma-Aldrich) at concentration of 100 μM.

All experiments were conducted in
an UHV system composed of three interconnected chambers for PLD, OMBE,
and STM/STS characterization. Au(111)/mica substrates (Mateck) were
cleaned by cycles of Ar⁺ sputtering (1 keV) and annealing
at 700 K. MoS₂ was deposited by PLD on freshly prepared
Au(111) at room temperature (RT) and subsequently annealed at 730
K for 30 min. The PLD process was optimized to obtain a submonolayer
coverage of well-ordered single-layer MoS₂ nanocrystals.
Briefly, a rotating MoS₂ target (Testbourne) was ablated
by KrF laser pulses (248 nm wavelength, 10 ns pulse duration) at a
repetition rate of 1 pulse per second and a laser fluence of 2 J/cm². The desired MoS₂ coverage on the substrate—placed
at 3 cm from the target—was achieved with six laser pulses.
Pentacene (Sigma Aldrich, 98% purity) was deposited on MoS₂/Au(111) samples at RT from an effusion cell (Dr. Eberl–MBE
Komponenten) heated at 428 K. A mild annealing at 350 K was performed
after deposition.

Figure 1 shows the device fabrication process, along with the device architecture. PS (average Mw ~ 280,000) and pentacene were purchased from Sigma-Aldrich (Sigma-Aldrich, St. Louis, MO, USA) and TCI (TCI, Tokyo, Japan), respectively. Indium tin oxide (ITO) glass substrate was cleaned in acetone, deionized water, and isopropyl alcohol for 15 min each by an ultrasonic bath sequentially. A 540 nm PS dielectric was formed by spin-coating a solution of PS in xylene (6 wt.%) on the substrate at room temperature. Then, the dielectric layer was baked at 120°C for 1 hr to completely remove residual solvents. Prior to the deposition of pentacene, the devices were exposed to UV light of 185 and 253.7 nm (SunMonde, UV-O₃ Cleaner, 40 W, Shanghai, China) for 0 ~ 240 s. Then, pentacene was evaporated under 3 × 10^-4 Pa at a rate of 0.2 ~ 0.3 Å/s to form a film with 30 nm. At last, gold source and drain electrodes of 50 nm were thermal evaporated using a metal shadow mask without breaking the vacuum.