Multilayer films of organic compounds on solid surfaces have been studied for more than 60 years because they allow fabrication of multicomposite molecular assemblies of tailored architecture. However, both the Langmuir-Blodgett technique and chemisorption from solution can be used only with certain classes of molecules. An alternative approach—fabrication of multilayers by consecutive adsorption of polyanions and polycations—is far more general and has been extended to other materials such as proteins or colloids. Because polymers are typically flexible molecules, the resulting superlattice architectures are somewhat fuzzy structures, but the absence of crystallinity in these films is expected to be beneficial for many potential applications.

https://science.sciencemag.org/content/sci/277/5330/1232.full.pdf

Fuzzy Nanoassemblies: Toward Layered Polymeric Multicomposites

Organic solar cell research has developed during the past 30 years, but especially in the last decade it has attracted scientific and economic interest triggered by a rapid increase in power conversion efficiencies. This was achieved by the introduction of new materials, improved materials engineering, and more sophisticated device structures. Today, solar power conversion efficiencies in excess of 3% have been accomplished with several device concepts. Though efficiencies of these thin-film organicdevices have not yet reached those of their inorganic counterparts (η ≈ 10–20%); the perspective of cheap production (employing, e.g., roll-to-roll processes) drives the development of organic photovoltaic devices further in a dynamic way. The two competitive production techniques used today are either wet solution processing or dry thermal evaporation of the organic constituents. The field of organic solar cells profited well from the development of light-emitting diodes based on similar technologies, which have entered the market recently. We review here the current status of the field of organic solar cells and discuss different production technologies as well as study the important parameters to improve their performance.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0884291400094498

Organic solar cells: An overview

The emergence of semiconductor nanocrystals as the building blocks of nanotechnology has opened up new ways to utilize them in next generation solar cells. This paper focuses on the recent developments in the utilization of semiconductor quantum dots for light energy conversion. Three major ways to utilize semiconductor dots in solar cell include (i) metal−semiconductor or Schottky junction photovoltaic cell (ii) polymer−semiconductor hybrid solar cell, and (iii) quantum dot sensitized solar cell. Modulation of band energies through size control offers new ways to control photoresponse and photoconversion efficiency of the solar cell. Various strategies to maximize photoinduced charge separation and electron transfer processes for improving the overall efficiency of light energy conversion are discussed. Capture and transport of charge carriers within the semiconductor nanocrystal network to achieve efficient charge separation at the electrode surface remains a major challenge. Directing the future resear...

http://wiki.phy.queensu.ca/shughes/images/d/d1/Quantum_Dot_Solar_Cells._Semiconductor_Nanocrystals_as_Light_Harvesters.pdf

Quantum Dot Solar Cells. Semiconductor Nanocrystals as Light Harvesters

A review was presented to demonstrate a historical description of the synthesis of light-emitting conjugated polymers for applications in electroluminescent devices. Electroluminescence (EL) was first reported in poly(para-phenylene vinylene) (PPV) in 1990 and researchers continued to make significant efforts to develop conjugated materials as the active units in light-emitting devices (LED) to be used in display applications. Conjugated oligomers were used as luminescent materials and as models for conjugated polymers in the review. Oligomers were used to demonstrate a structure and property relationship to determine a key polymer property or to demonstrate a technique that was to be applied to polymers. The review focused on demonstrating the way polymer structures were made and the way their properties were controlled by intelligent and rational and synthetic design.

Synthesis of Light-Emitting Conjugated Polymers for Applications in Electroluminescent Devices

Synthetic Principles for Bandgap Control in Linear pi-Conjugated Systems.

Solvatochromic shifts of spectra of solutions of poly(3-hexylthiophene) and poly(3-docosylthiophene) have been analyzed in terms of Taft linear solvation energy relationships. Color changes of solutions of the former at 25°C are primarily due to changes in normal solute-solvent interactions. On the other hand, color changes of solutions of poly(3-docosylthiophene) appear to be due to configurational changes of the polymer chain. Solubility of the polymer is affected by solvation of the alkyl groups, electron donating or Lewis basicity properties of the solvent, polarity, and molecular volume of solvent molecules.

Dependence of absorption spectra and solubility of poly(3-alkylthiophene) on molecular structure of solvent

Electrical and optical properties of poly(3-alkylthiophene)

Anomalous dependences of luminescence of poly(3-alkylthiophene) on temperature and alkyl chain length

A remarkable absorption spectral change has been observed in ethylene propylene elastomer (EPR) films containing elongated poly(3-alkylthiophene). This change is explained in terms of the formation of new torsioned bonds between thiophene rings on the main polymer chains. This interpretation is also consistent with the anisotropy of the polarization dependence of absorption.

Mitsuyoshi Onoda

Papers

Dependence of absorption spectra and solubility of poly(3-alkylthiophene) on molecular structure of solvent

Electrical and optical properties of poly(3-alkylthiophene)

Anomalous dependences of luminescence of poly(3-alkylthiophene) on temperature and alkyl chain length

Effect of polymer elongation on the absorption spectrum of poly(3-alkylthiophene)

Actuator based on doping/undoping-induced volume change in anisotropic polypyrrole film