Current Organic Chemistry - Volume 11, Issue 14, 2007

The present issue of Current Organic Chemistry is devoted to organic functional materials with special emphasis on material design, synthesis and relationship between structure-application performance. The authors provide us an up-to-date discussion on the special application area, such as PLED, OFET, DSSCs and photochromism. Polyfluorene-based conjugated polyelectrolytes (CPs) exhibit excellent unique characteristics different from the traditional conjugated polymers used in PLEDs, which is extensively reviewed by Prof. Yong Cao et. al. at South China University of Technology. The review was focusing on the design, synthesis of the material and their application in PLEDs. And then, Dr. Wan, from California University at Los Angeles show us recent progress on molecular design and synthesis of polycyclic aromatic compounds, such as oligoarenes, oligoacenes, TTF derivatives and disc-like polycyclic aromatic hydrocarbons, for Organic Field-effect Transistors (OFET). Dye-sensitized solar cells (DSSCs) have attracted considerable attention in both academic and industrial community as a cost-effective alternative to conventional solar cells. Development of both metal-free organic dye and metal-ligand complexes for DSSCs have reached great achievements on device performance. Both kinds of materials applying to DSSCs are summarized by Prof. Li et al, from Fudan University and Prof. Guo et al, from Zhengzhou University, respectively and showing us what has been going on in the field. Due to potential photonic applications, photochromism is another hot point in the community. Diarylethene has been studied extensively. Dr. Chen at General Electric summarized the progress on design, synthesis and its photochromic performance of diarylethenes.

Conjugated Polyelectrolytes (CPs) have been successfully used as highly sensitive materials in chemo and biosensors for many years. But in general CPs were not very successful as a light emitting layer in polymer light-emitting diodes (PLEDs). Until recently, it was found that polyfluorene-based CPs and their precursors showed excellent unique characteristics different from the traditional conjugated polymers as light-emitting materials. In this review we summarize recent work on the design, synthesis of polyfluorene-based CPs and their precursors and their successful use in PLEDs.

This review is focused on current state of materials design and syntheses of organic semiconductors for thinfilm field effect transistors (FETs). Recently, high performance p- or n-type organic FETs with high charge carrier mobility, high ON-OFF current ratios and high stability have been achieved due to the improvement of materials syntheses. Intrinsic electronic properties, solid-state packing, stability, and the capability of easy processing are the main issues of molecular design of these semiconductors. Various polycyclic aromatic compounds such as oligoarenes, oligoacenes, tetrathiafulvalenes and disc-like polycyclic aromatic hydrocarbons are qualified as good candidates for FETs after accurate chemical tailoring. We will give an overview of most recent progress in the materials synthesis and the consequential device properties.

Dye-sensitized solar cells (DSSCs) have received considerable attentions as a cost-effective alternative to conventional solar cells. One of main issues for the development of DSSCs is the design and synthesis of dyes that serve as light absorbers for energy conversion. Up to now, many different pure organic dyes and transition metal complexes have been evaluated as sensitizers. DSSCs sensitized with pure organic dyes have relatively lower power conversion efficiencies than those sensitized with metal complexes. However, pure organic dyes have many advantages for their application in DSSCs, such as lower cost, higher absorption coefficient and easy control of redox potentials of LUMO and HOMO levels. Importantly, the highest power conversion efficiency of DSSCs with pure organic dyes has reached 8.0%, which is close to that (∼10%) of DSSCs with metal complexes. In this paper, the features of pure organic dyes and several ways for the design towards higher efficiency are presented. The recent progress on the selection and utilization of these pure organic dyes, especially organic D-π-A dyes, are mainly discussed. The effects of the structures of organic D-π-A dyes on cell performances are compared.

Photochromic diarylethene have received considerable attention because of their potential photonic applications. All of these applications come from the fact that when stimulated with light at appropriate wavelengths, the physical and chemical properties can be reversibly modulated. During the last decade, more and more decoration on the general structures of diarylethene and novel skeletons beyond the general structures have been developed from many motivation aspects, such as seeking for facile synthetic routes, the ability to tailor the physical and chemical properties in flexible manner and etc. This article describes recent novel development of molecular structure design strategies of diarylethene.

Dye sensitized solar cells (DSSCs) have great potential to challenge the traditional silicon-based semiconductor solar cells in the photovoltaic (PV) market because of their low cost and medium efficiency. This type of solar cell has achieved an impressive photo-to-energy conversion efficiency of over 10%. In a dye sensitized solar cell, the charge separation is initiated at the adsorbed dye, which was bound at the interface of an inorganic semiconductor film and a hole transport material. The dye is the key component in such cells. In order to optimize the performance of such devices, it is important to design suitable dyes with tunable spectroscopic and electrochemical properties. Careful modification of the structures of the sensitizers can improve light harvesting in the visible and near-IR region with high optical extinction coefficients and enhance the performance of the devices. It's necessary to optimize the properties of the dye in conjunction with other factors in order to best exploit and be fully compatible with other cell modifications in the development of cheap and efficient photovoltaic systems. In this review, current strategies for the molecular engineering of the dyes based on ruthenium complexes possessing different functionalized ligands are discussed.