Recent Advances in Bulk Heterojunction Polymer Solar Cells

: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Arylamine organic dyes with donor (D), π-bridge (π) and acceptor (A) moieties for dye-sensitized solar cells (DSCs) have received great attention in the last decade because of their high molar absorption coefficient, low cost and structural variety. In the early stages, the efficiency of DSCs with arylamine organic dyes with D–π–A character was far behind that of DSCs with ruthenium(II) complexes partly due to the lack of information about the relationship between the chemical structures and the photovoltaic performance. However, exciting progress has been recently made, and power conversion efficiencies over 10% were obtained for DSCs with arylamine organic dyes. It is thus that the recent research and development in the field of arylamine organic dyes employing an iodide/triiodide redox couple or polypyridyl cobalt redox shuttles as the electrolytes for either DSCs or solid-state DSCs has been summarized. The cell performance of the arylamine organic dyes are compared, providing a comprehensive overview of arylamine organic dyes, demonstrating the advantages/disadvantages of each class, and pointing out the field that needs to reinforce the research direction in the further application of DSCs.

Arylamine organic dyes for dye-sensitized solar cells

Xugang Guo,*,† Antonio Facchetti,*,‡,§ and Tobin J. Marks*,‡ †Department of Materials Science and Engineering, South University of Science and Technology of China, No. 1088, Xueyuan Road, Shenzhen, Guangdong 518055, China ‡Department of Chemistry and the Materials Research Center, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, United States Polyera Corporation, 8045 Lamon Avenue, Skokie, Illinois 60077, United States

Imide- and Amide-Functionalized Polymer Semiconductors

Although fullerenes and their derivatives, such as PCBM, have been the dominant electron-acceptor materials in organic photovoltaic cells (OPVs), they suffer from some disadvantages, such as weak absorption in the visible spectral region, limited spectral breadth and difficulty in variably tuning the band gap. It is necessary to explore non-fullerene electron acceptors that will not only retain the favorable electron-accepting and transporting properties of fullerenes but also overcome their insufficiencies. After a decade of mediocrity, non-fullerene acceptors are undergoing rapid development and are emerging as a hot area of focus in the field of organic semiconductors. Solution-processed bulk heterojunction (BHJ) OPVs based on non-fullerene acceptors have shown encouraging power conversion efficiencies of over 4%. This article reviews recent developments in several classes of solution-processable non-fullerene acceptors for BHJ OPVs. The remaining problems and challenges along with the key research directions in the near future are discussed.

Non-fullerene acceptors for organic photovoltaics: an emerging horizon

Perylene diimides based materials for organic solar cells

Polymer solar cells based on fullerene acceptors have reached in recent years power conversion efficiencies (PCEs) approaching 13%. The advent of non-fullerene acceptors (NFAs) with the advantages of synthetic versatility, a strong absorption ability and high thermal stability has resulted in impressive PCEs of over 18% in single junction devices. The insertion of interlayers between the active components and electrodes plays a key role in charge collection, boosts the efficiency and improves the device stability. However, the mechanisms regulating the interaction between interlayer materials and active layers based on NFAs are not yet completely rationalized. This review article summarizes organic, inorganic and hybrid materials used as anode and cathode interlayers in conventional and inverted fullerene-free solar cells. Particular attention is paid to the distinctive features of the interlayers when used in non-fullerene solar cells. We will also comment on the fabrication processes with an emphasis on the transition from small area, lab devices to large area modules and on possible mechanisms which are behind.

Interlayers for non-fullerene based polymer solar cells: distinctive features and challenges

We report on the photophysical characterization of two solution-processable red-emissive perylene diimide molecules and on their use in fully solution assembled OLEDs. The two emitters contain sterically hindered aromatic naphthalene or acenaphthene substituents on the perylene core. These fused rings limits the perylene diimide intermolecular π–π interactions in the solid state due to highly sterically hindered effects, while preserving an extended conjugation between the substituents and the perylene core. Indeed, these features generate a broad absorption for both perylene derivatives along with an efficient red and deep red emission in the solid state for the PDIs with naphthalene and acenaphthene, respectively. The performances of both emitters were tested on OLEDs, where the active layer is a film of bulk PDI, fabricated by simple solution processing. The devices with acenaphthene-substituted perylene diimide provide deep red electroluminescence with emission wavelength at 690 nm, CIE coordinates of (x = 0.69, y = 0.29) and show the best efficiency reported so far for OLED based on PDI fluorescent emitters.

Perylene diimide derivatives as red and deep red-emitters for fully solution processable OLEDs

Synthesis and characterization of new electron acceptor perylene diimide molecules for photovoltaic applications

Two new organic sensitizers for dye solar cells containing a sterically hindered moiety have been synthesized. The introduction of a 3,4-dibutyl-thiophene ring into D-π-A dyes reduces the sensitize ...

Erika Kozma

Papers

Perylene diimides based materials for organic solar cells

Interlayers for non-fullerene based polymer solar cells: distinctive features and challenges

Perylene diimide derivatives as red and deep red-emitters for fully solution processable OLEDs

Synthesis and characterization of new electron acceptor perylene diimide molecules for photovoltaic applications

Metal-free organic sensitizers with a sterically hindered thiophene unit for efficient dye-sensitized solar cells