Dopant-Stabilized Assembly of Poly(3-hexylthiophene).

Polymer self-assembly is a powerful approach for forming nanostructures for solution-phase applications. However, polymer semiconductor assembly has primarily been driven by solvent interactions. Here, we report poly(3-hexythiophene) homopolymer assembly driven and stabilized by oxidative doping with iron (III) p-toluenesulfonate in benzonitrile. By this improved method, dopant mol % and addition temperature determine the size and morphology of oxidized polymer nanostructures. The dopant counterion provides colloidal stability in a process of dopant-stabilized assembly (DSA). Each variable governing polymer assembly is systematically varied, revealing general principles of oxidized nanostructure assembly and allowing the polymer planarity, optical absorption, and doping level to be modulated. Oxidized nanostructure heights, lengths, and widths are shown to depend on these properties, which we hypothesize is due to competing nanostructure formation and oxidation mechanisms that are governed by the polymer conformation upon doping. Finally, we demonstrate that the nanoparticle oxidative doping level can be tuned post-formation through sequential dopant addition. By revealing the fundamental processes underlying DSA, this work provides a powerful toolkit to control the assembly and optoelectronic properties of oxidatively doped nanostructures in solution.

Polyacetylene Revisited: A Computational Study of the Molecular Engineering of N-type Polyacetylene.

The development of stable and highly conductive polymers, particularly n-type materials, remains an outstanding challenge in organic electronics. N-doped polyacetylene has long been studied as a highly conductive organic n-type material but suffers from extremely poor stability. Herein, we use DFT to model a series of n-doped polyacetylene derivatives, which have been functionalized with a range of electron-withdrawing substituents, with the goal of identifying attractive candidates for synthesis. We analyze the predicted molecular orbital energies, polymer planarity, and delocalization of charge carriers along the polymer backbone. In so doing, we develop key insights about the ideal substituents for both stable and highly conductive polyacetylene derivatives. This work will inform the modern synthesis and development of new polyacetylene derivatives. Beyond this, the work identifies a variety of new materials that have not yet been synthesized and should be good candidates for emerging optoelectronic applications including soft thermoelectrics, bioelectronics, and flexible device technologies.

Programmable Assembly of π-Conjugated Polymers.

π-Conjugated polymers have numerous applications due to their advantageous optoelectronic and mechanical properties. These properties depend intrinsically on polymer ordering, including crystallinity, orientation, morphology, domain size, and π-π interactions. Programming, or deliberately controlling the composition and ordering of π-conjugated polymers by well-defined inputs, is a key facet in the development of organic electronics. Here, π-conjugated programming is described at each stage of material development, stressing the links between each programming mode. Covalent programming is performed during polymer synthesis such that complex architectures can be constructed, which direct polymer assembly by governing polymer orientation, π-π interactions, and morphological length-scales. Solution programming is performed in a solvated state as polymers dissolve, aggregate, crystallize, or react in solution. Solid-state programming occurs in the solid state and is governed by polymer crystallization, domain segregation, or gelation. Recent progress in programming across these stages is examined, highlighting order-dependent features and assembly techniques that are unique to π-conjugated polymers. This should serve as a guide for delineating the many ways of directing π-conjugated polymer assembly to control ordering, structure, and function, enabling the further development of organic electronics.

High-Throughput Screening of Antisolvents for the Deposition of High-Quality Perovskite Thin Films.

One-step solution deposition of high-quality perovskite thin films relies heavily on a small number of antisolvents. Here, we design a simple minimum volume colorimetric solution assay to screen over 100 different solvents. We correctly identify 14 previously reported antisolvents and predict 20 novel candidates. We then refine the assay through analysis of screening results, available solvent properties, and qualitative evaluation of films cast using 50 candidates. Using the refined findings, we successfully demonstrated 15 different antisolvents for characterization and evaluation in inverted devices, including six previously unreported candidates. All candidates produced power conversion efficiencies comparable to chlorobenzene controls without any additional optimization. This work presents the largest scope of antisolvents reported, can be easily adapted to other perovskites, and opens the door to selecting antisolvents based on a wide range of desirable properties including efficiency, usability, safety, and industrial viability.

Oxidation promoted self-assembly of π-conjugated polymers.

Self-assembly is an attractive strategy for organizing molecules into ordered structures that can span multiple length scales. Crystallization Driven Self-Assembly (CDSA) involves a block copolymer with a crystallizable core-forming block and an amorphous corona-forming block that aggregate into micelles with a crystalline core in solvents that are selective for the corona block. CDSA requires core- and corona-forming blocks with very different solubilities. This hinders its use for the self-assembly of purely π-conjugated block copolymers since blocks with desirable optoelectronic properties tend to have similar solubilities. Further, this approach is not readily reversible, precluding stimulus-responsive assembly and disassembly. Here, we demonstrate that selective oxidative doping of one block of a fully π-conjugated block copolymer promotes the self-assembly of redox-responsive micelles. Heteroatom substitution in polychalcogenophenes enables the modulation of the intrinsic polymer oxidation potential. We show that oxidized micelles with a narrow size distribution form spontaneously and disassemble in response to a chemical reductant. This method expands the scope of π-conjugated polymers that can undergo controlled self-assembly and introduces reversible, redox-responsive self-assembly of π-conjugated polymers.