Synthesis and application of H-Bonded cross-linking polymers containing a conjugated pyridyl H-Acceptor side-chain polymer and various carbazole-based H-Donor dyes bearing symmetrical cyanoacrylic acids for organic solar cells

Self-Assembled Organic Materials for Photovoltaic Application

Organic photovoltaic cells based on bulk-heterojunction architecture have been a topic of intense research for the past two decades. Recent reports on power conversion efficiency surpassing 10% suggest these devices are a viable low-cost choice for a range of applications where conventional silicon solar cells are not suitable. Further improvements in efficiency could be achieved with the enhanced interaction between the donor and acceptor components. Effective utilization of supramolecular interactions to tailor and manipulate the communication between the components in the blend is a good strategy towards this end. Literature reports suggest that the long-term stability of organic solar cells, a major hurdle for commercial applications, can also be partially addressed by generating stable supramolecular nanostructures. In this review, we have made an attempt to summarize advances in small molecule, oligomer and polymer based systems, wherein supramolecular interactions such as hydrogen-bonding, pi-pi stacking, and dipole-dipole are explored for realizing stable and efficient bulk-heterojunction solar cells.

Synthesis, photophysical and thin-film self-assembly properties of novel fluorescent molecules with carbon-carbon triple bonds

Three novel fluorescent molecules with carbon-carbon triple bonds 2TBEA, 2TBDA and TEPEB are successfully designed and synthesized. Their thermal, photophysical, electrochemical, electronic and thin-film self-assembly properties were characterized. Three dyes showed typical photoluminescence (PL) emission behaviors, the PL intensities firstly increased and then decreased with gradually decreasing concentration. The appealing fluorescence properties indicated that three dyes could be used as good fluorescent materials. Additionally, the thin-film self-assembly behaviors of three dyes were also investigated. The microstructures of their optical microscopy (OM) images exhibited high flexibility. Furthermore, SEM and AFM surface morphology of these self-assembly nanostructures revealed that three well-defined long-range order of rod-like and tube-like self-assembly systems exhibited interesting morphology properties. Therefore, three compounds may be of great interest for the development of organic thin-film materials.

Hydrogen bonding in bulk heterojunction solar cells: a case study

Small molecules with dithieno[3,2-b;2',3'-d]thiophene as central building block and octyl cyanoacetate and octyl cyanoacetamide as different terminal building blocks have been designed and synthesized. The amide containing small molecule can form intermolecular hydrogen bonding between N-H...O = C of the amide group. The photovoltaic properties and active layer morphologies of the two molecules in bulk heterojunction solar cells are compared to study the influence of hydrogen bonding on the active layer morphology. New methanofullerene compound containing amide group has also been synthesized and compared with conventional fullerene electron acceptors.

Effects of cyano (CN)-groups on the planarity, film morphology and photovoltaic performance of benzodithiophene-based polymers

A class of polymers (POT-DH, POT-HCN and POT-DCN) were synthesized and they contain the same donor (BDT) and acceptor units but different numbers of cyano (CN)-groups, i.e. 0, 1 and 2.

Synthesis and self-association of double-helical AADD arrays

The design and syntheses of four self-complementary oligomers that contain an underlying AADD hydrogen bond sequence are presented, and their self-association was examined in the solution and solid state. The molecular recognition between the two strands is highly sensitive to substitutions of their component heterocycles. Substitution with electron-donating and -withdrawing groups and the influence of preorganization has a large effect on the overall stabilities of the complexes studied. In particular, a wide range (>10(5) M(-1)) of stabilities with respect to substitutions at various positions in the AADD oligomers was demonstrated. In the most extreme case, the dimerization constant measured (K(dimer) ≥4.5×10(7) M(-1)) is comparable to the most stable homodimers of neutral AADD arrays reported to date.

Density functional theory (DFT) study of triphenylamine-based dyes for their use as sensitizers in molecular photovoltaics

In this work we studied three dyes which are proposed for potential photovoltaic applications and named Dye7, Dye7-2t and Dye7-3t. The Density Functional Theory (DFT) was utilized, using the M05-2X hybrid meta-GGA functional and the 6–31+G(d,p) basis set. This level of calculation was used to find the optimized molecular structure and to predict the main molecular vibrations, the absorption and emission spectra, the molecular orbitals energies, dipole moment, isotropic polarizability and the chemical reactivity parameters that arise from Conceptual DFT. Also, the pK_a values were calculated with the semi-empirical PM6 method.

Stability of polymer solar cells

Organic photovoltaics (OPVs) evolve in an exponential manner in the two key areas of efficiency and stability. The power conversion efficiency (PCE) has in the last decade been increased by almost a factor of ten approaching 10%. A main concern has been the stability that was previously measured in minutes, but can now, in favorable circumstances, exceed many thousands of hours. This astonishing achievement is the subject of this article, which reviews the developments in stability/degradation of OPVs in the last five years. This progress has been gained by several developments, such as inverted device structures of the bulk heterojunction geometry device, which allows for more stable metal electrodes, the choice of more photostable active materials, the introduction of interfacial layers, and roll-to-roll fabrication, which promises fast and cheap production methods while creating its own challenges in terms of stability.