Synthesis of a Conjugated Polymer with Broad Absorption and Its Application in High-Performance Phototransistors

An amorphous copolymer (PBDT–BBT) of 4,8-bis­(2-thienyl)­benzo­[1,2-<i>b</i>:4,5-<i>b</i>′]­dithiophene and 5,5′-bibenzo­[<i>c</i>]­[1,2,5]­thiadiazole was synthesized by Stille coupling polymerization. PBDT–BBT exhibited good solution processability, excellent thermal stability with decomposition temperature of 437 °C, broad absorption (300–800 nm), deep HOMO level (−5.7 eV), and LUMO level (−3.7 eV). The microstructure order of PBDT–BBT thin films is not susceptible to thermal annealing temperature (80–200 °C). Field-effect transistors based on this polymer exhibited a charge-carrier mobility of 6 × 10^–3 cm² V^–1 s^–1, threshold voltage of −1 V, and on/off current ratio of 10⁶ without any post-treatments. Thin film phototransistors of PBDT–BBT exhibited a photoresponsivity of 3200 mA W^–1 and photocurrent/dark current ratio of 4 × 10⁵

Topological Structural Transformations of Nanoparticle Self-Assemblies Mediated by Phase Transfer and Their Application as Organic–Inorganic Hybrid Photodetectors

Nanoparticle (NP) self-assemblies have attracted an increasing amount of attention in recent years because of their potential application in the construction of novel nanodevices. The controllable transformation of NP self-assemblies (NPS) between a polar and nonpolar environment is required for many specific applications because of their different properties in different environments. In this article, water-soluble luminescent CdS/CdTe NPS were synthesized using thioglycolic acid as a capping agent. The stiff and straight NPS bundles became loose after phase transfer from an aqueous to an organic phase. Subsequently, the NPS transferred to the aqueous phase. The loose structure transformed into many twisted nanoribbons. Additionally, hybrid photodetectors made using the organic-soluble NPS and P3HT polymers were fabricated, and we found that the NPS/P3HT blend may be perfect for light detection. The organic-soluble NPS are potentially useful for the fabrication of semiconductor nanojunctions

High Performance Nanocrystals of a Donor–Acceptor Conjugated Polymer

Highly crystalline, well-defined nanowires of a donor–acceptor (D–A) conjugated polymer based on bithiazole-thiazolothiazole (PTz) were successfully prepared by a facile solution self-assembly method. In PTz nanowires, polymer chains align along the long axis of the nanowires forming lamellar structures with close π-stacking perpendicular to the long axis of the nanowires. The nanowires possess a single crystal structure with orthorhombic crystal unit cell in which the lattice parameters are <i>a</i> ≈ 21.05 Å, <i>b</i> ≈ 6.94 Å, and <i>c</i> ≈ 4.64 Å. The intrinsic charge transport property of PTz was characterized by using its single crystal nanowires in field-effect transistors with a mobility up to 0.46 cm² V^–1 s^–1. As an example of PTz single crystal nanowires in optoelectronic application, phototransistors of PTz nanowires exhibited a photoresponsivity up to 2531 A W^–1 and a photosensitivity up to 1.7 × 10⁴

Soft-Etching Copper and Silver Electrodes for Significant Device Performance Improvement toward Facile, Cost-Effective, Bottom-Contacted, Organic Field-Effect Transistors

Poor charge injection and transport at the electrode/semiconductor contacts has been so far a severe performance hurdle for bottom-contact bottom-gate (BCBG) organic field-effect transistors (OFETs). Here, we have developed a simple, economic, and effective method to improve the carrier injection efficiency and obtained high-performance devices with low cost and widely used source/drain (S/D) electrodes (Ag/Cu). Through the simple electrode etching process, the work function of the electrodes is more aligned with the semiconductors, which reduces the energy barrier and facilitates the charge injection. Besides, the formation of the thinned electrode edge with desirable micro/nanostructures not only leads to the enlarged contact side area beneficial for the carrier injection but also is in favor of the molecular self-organization for continuous crystal growth at the contact/active channel interface, which is better for the charge injection and transport. These effects give rise to the great reduction of contact resistance and the amazing improvement of the low-cost bottom-contact configuration OFETs performance

Fullerene/Sulfur-Bridged Annulene Cocrystals: Two-Dimensional Segregated Heterojunctions with Ambipolar Transport Properties and Photoresponsivity

Fullerene/sulfur-bridged annulene cocrystals with a two-dimensional segregated alternating layer structure were prepared by a simple solution process. Single-crystal analysis revealed the existence of continuing π–π interactions in both the donor and acceptor layers, which serve as transport paths for holes and electrons separately. The ambipolar transport behaviors were demonstrated with single-crystal field-effect transistors and rationalized by quantum calculations. Meanwhile, preliminary photoresponsivity was observed with the transistor configuration

Fullerene/Sulfur-Bridged Annulene Cocrystals: Two-Dimensional Segregated Heterojunctions with Ambipolar Transport Properties and Photoresponsivity

Fullerene/sulfur-bridged annulene cocrystals with a two-dimensional segregated alternating layer structure were prepared by a simple solution process. Single-crystal analysis revealed the existence of continuing π–π interactions in both the donor and acceptor layers, which serve as transport paths for holes and electrons separately. The ambipolar transport behaviors were demonstrated with single-crystal field-effect transistors and rationalized by quantum calculations. Meanwhile, preliminary photoresponsivity was observed with the transistor configuration