Organic Semiconductor Growth and Morphology Considerations for Organic Thin‐Film Transistors

Abstract

Analogous to conventional inorganic semiconductors, the performance of organic semiconductors is directly related to their molecular packing, crystallinity, growth mode, and purity. In order to achieve the best possible performance, it is critical to understand how organic semiconductors nucleate and grow. Clever use of surface and dielectric modification chemistry can allow one to control the growth and morphology, which greatly influence the electrical properties of the organic transistor. In this Review, the nucleation and growth of organic semiconductors on dielectric surfaces is addressed. The first part of the Review concentrates on small-molecule organic semiconductors. The role of deposition conditions on film formation is described. The modification of the dielectric interface using polymers or self-assembled mono-layers and their effect on organic-semiconductor growth and performance is also discussed. The goal of this Review is primarily to discuss the thin-film formation of organic semiconducting species. The patterning of single crystals is discussed, while their nucleation and growth has been described elsewhere (see the Review by Liu et. al).([¹]) The second part of the Review focuses on polymeric semiconductors. The dependence of physico-chemical properties, such as chain length (i.e., molecular weight) of the constituting macromolecule, and the influence of small molecular species on, e.g., melting temperature, as well as routes to induce order in such macromolecules, are described.

Block copolymer strategies for solar cell technology

“…31 During casting and subsequent annealing processes, there is a process of crystallization, alignment of polymer chains, and limited self-organization, which changes the structure to favor exciton collection and charge transport. 50,51 This process is extremely sensitive to the solvent used, 52,53 variations in composition, 54 annealing, [55][56][57][58][59] chemical-structure variations, [60][61][62][63] purities, 64 and processing conditions, 65 to name but a few of the related parameters when dealing with what is a fundamentally unstable system. 66 The seminal work by Yang et al demonstrated the necessity of controlled mixing of the acceptor and donor in the composite.…”

Reversible Optical Control of Conjugated Polymer Solubility with Sub-micrometer Resolution

“…2,3,11,14,28 Unfortunately, none of these methods are universally effective and many require numerous processing steps, reducing the cost advantage of solution-processing. Cross-linking reactions permanently alter the chemical structure and generally require chemical tailoring, which usually results in degraded material properties.…”

Structure and Morphology Control in Thin Films of Conjugated Polymers for an Improved Charge Transport

“…However, clarifying the detailed, bottom-up relationship between materials and performance has been always challenging since the discovery of semi-conducting conjugated polymers. After the related research for several decades, a great progress has been made in this field [2,3,[19][20][21][22][23][24][25][26][27][28][29], i.e., proposing more clear and efficient synthesis guidelines, concluding principles to improve morphological order and revealing the importance of morphological and structural features in films to the final performance. Now, synthesis of more efficient π-conjugated systems and improvement of order in films have become the essential problems for the development of opto-electronic functional conjugated polymers in terms of chemistry and physics, respectively.…”