-phenylenevinylene)s L4. Fluorene-Based Conjugated Polymers L4.1. Fluorene-Based Copolymers ContainingElectron-Rich MoietiesM4.2. Fluorene-Based Copolymers ContainingElectron-Deﬁcient MoietiesN4.3. Fluorene-Based Copolymers ContainingPhosphorescent ComplexesQ5. Carbazole-Based Conjugated Polymers R5.1. Poly(2,7-carbazole)-Based Polymers R5.2. Indolo[3,2-

https://ir.nctu.edu.tw:443/bitstream/11536/6508/1/000271856900020.pdf

Synthesis of Conjugated Polymers for Organic Solar Cell Applications

This article is written from an organic chemist's point of view and provides an up-to-date review about organic solar cells based on small molecules or oligomers as absorbers and in detail deals with devices that incorporate planar-heterojunctions (PHJ) and bulk heterojunctions (BHJ) between a donor (p-type semiconductor) and an acceptor (n-type semiconductor) material. The article pays particular attention to the design and development of molecular materials and their performance in corresponding devices. In recent years, a substantial amount of both, academic and industrial research, has been directed towards organic solar cells, in an effort to develop new materials and to improve their tunability, processability, power conversion efficiency, and stability. On the eve of commercialization of organic solar cells, this review provides an overview over efficiencies attained with small molecules/oligomers in OSCs and reflects materials and device concepts developed over the last decade. Approaches to enhancing the efficiency of organic solar cells are analyzed.

Small molecule organic semiconductors on the move: promises for future solar energy technology.

Organic photovoltaic cells (OPVs) are a promising cost-effective alternative to silicon-based solar cells, and possess light-weight, low-cost, and flexibility advantages. Significant progress has been achieved in the development of novel photovoltaic materials and device structures in the last decade. Nowadays small molecular semiconductors for OPVs have attracted considerable attention, due to their advantages over their polymer counterparts, including well-defined molecular structure, definite molecular weight, and high purity without batch to batch variations. The highest power conversion efficiencies of OPVs based on small molecular donor/fullerene acceptors or polymeric donor/fullerene acceptors are up to 6.7% and 8.3%, respectively, and meanwhile nonfullerene acceptors have also exhibited some promising results. In this review we summarize the developments in small molecular donors, acceptors (fullerene derivatives and nonfullerene molecules), and donor–acceptor dyad systems for high-performance multilayer, bulk heterojunction, and single-component OPVs. We focus on correlations of molecular chemical structures with properties, such as absorption, energy levels, charge mobilities, and photovoltaic performances. This structure–property relationship analysis may guide rational structural design and evaluation of photovoltaic materials (253 references).

Small molecule semiconductors for high-efficiency organic photovoltaics

Although most research in the field of organic bulk heterojunction solar cells has focused on combinations of a p-type conducting polymer as a donor and a fullerene-based acceptor, recent work has demonstrated the viability of solution-processed heterojunctions composed entirely of molecular solids. Molecular solids offer potential advantages over conjugated polymer systems in terms of easier purification, amenability to mass-scale production and better batch-to-batch reproducibility. This article reviews the major classes of molecular donors that have been reported in the literature in the past several years and highlights some of key considerations in molecular heterojunction design compared to polymer-based bulk heterojunctions.

Small Molecule Solution-Processed Bulk Heterojunction Solar Cells†

Heterojunctions in Solar Cells. Lessons Learned from the Benchmark Poly(3-hexylthiophene):[6,6]-Phenyl‐C61-butyric Acid Methyl Ester System Minh Trung Dang,† Lionel Hirsch,‡ Guillaume Wantz,‡ and James D. Wuest*,† †Deṕartement de Chimie, Universite ́ de Montreál, Pavillon J.-Armand Bombardier, 2900 boulevard Édouard-Montpetit, Montreál, Queb́ec H3T 1J4, Canada ‡Laboratoire de l'Inteǵration du Mateŕiau au System̀e, Universite ́ de Bordeaux, UMR CNRS 5218, École Nationale Supeŕieure de Chimie, Biologie et Physique, 16 Avenue Pey Berland, 33607 Pessac Cedex, France

Controlling the Morphology and Performance of Bulk Heterojunctions in Solar Cells. Lessons Learned from the Benchmark Poly(3-hexylthiophene):[6,6]-Phenyl-C61-butyric Acid Methyl Ester System

A series of novel soluble conjugated copolymers consisting of coplanar donor (bithiophenevinyl)−acceptor (2-pyran-4-ylidenemalononitrile) (TVM)-based unit coupled to different electron-donating ability moieties were synthesized by Suzuki coupling polymerization. The structures of the copolymers were characterized, and their physical properties were investigated. High molecular weight (Mn up to 43.8 kg/mol) and thermostable copolymers were obtained. The combination of TVM unit building block with gradually increased electron-donating ability moieties results in enhanced π−π stacking in solid state and intramolecular charge transfer (ICT) transition bands, which lead to an extension of their absorption spectral range. Cyclic voltammetry measurement displayed that the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of the copolymers can be fine-tuned. The resulting copolymers possessed relatively low HOMO energy levels promising good air stability and hi...

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Energy Level and Molecular Structure Engineering of Conjugated Donor−Acceptor Copolymers for Photovoltaic Applications

A series of novel soluble polythiophene derivatives containing triphenylamine moiety were synthesized by Grignard metathesis (GRIM) method. The structures of the polymers were characterized and their physical properties were investigated. High molecular weight (Mn up to 25,800 g/mol) and thermostable polymers were obtained. The absorption spectra demonstrated that the absorption wavelength of the polymers could be tuned dramatically by introducing thiophene units in the main chain of the polymers. Photoluminescence spectra indicated that there was intramolecular energy transfer from the side chain to the main chain, and the maximum emission was red-shifted gradually with the increase of thiophene units in the main chain. Cyclic voltammetry displayed that the polymers possessed relatively high oxidation potential, which promised good air stability and high open circuit voltage for photovoltaic cells application. Finally, bulk heterojunction photovoltaic devices were fabricated by using the polymers as donors and (6,6)-phenyl C61-butyric acid methyl ester (PCBM) as acceptor. The maximal open circuit voltage of the photovoltaic cells reached 0.71–0.87 V and the power conversion efficiencies of the devices were measured between 0.014% and 0.45% under white light at 100 mW/cm2. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3970–3984, 2008

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Synthesis and properties of polythiophene derivatives containing triphenylamine moiety and their photovoltaic applications

http://www.polymer.cn/UploadFile/research/200908281443351093.pdf

Solution-processable and thermal-stable triphenylamine-based dendrimers with truxene cores as hole-transporting materials for organic light-emitting devices

Three novel conjugated copolymers containing alkoxylated 4,7-diphenyl-2,1,3-benzothiadiazole and dialkylfluorene or dialkyloxyphenylene or dialkylthiophene units were prepared by Horner polycondensation reactions. They are all soluble in common organic solvents such as chloroform, tetrahydrofuran, and chlorobenzene. The novel copolymers were characterized by NMR, GPC, and elemental analysis. Thermogravimetric analysis of the copolymers showed they have good thermal stability with the decomposition temperature higher than 350 °C. Cyclic voltammetric study shows that the HOMO energy levels of the three copolymers are deep-lying which implies that these copolymers have good stability in the air and the relatively low HOMO energy level assures a higher open circuit potential when they are used in photovoltaic cells. Bulk-heterojunction photovoltaic cells were fabricated with the copolymers as the donors and PCBM as the acceptor. The cells based on the three copolymers exhibited power conversion efficiencies o...

http://www.polymer.cn/UploadFile/research/200908281615103750.pdf

Synthesis of 4,7-Diphenyl-2,1,3-Benzothiadiazole-Based Copolymers and Their Photovoltaic Applications

A symmetrical D-π-A-π-D organic dye molecule 2-{2,6-bis-[2-(4-diphenylamino-phenyl)-vinyl]-pyran-4-ylidene}-malononitrile (DADP) has been introduced into solution-processable organic solar cells (S-P OSCs). Detailed investigations on the relationship between its molecular structure and thermal, photophysical, electrochemical properties and electronic structure are described. The optimized bulk heterojunction solar cell based on DADP as donor and PCBM as acceptor with the configuration of ITO/PEDOT/DADP:PCBM/LiF/Al exhibits a Voc of 0.98 V, Isc of 4.16 mA/cm2, FF of 0.37, and power conversion efficiency (PCE) of 1.50% under the illumination of AM 1.5 simulated solar light (100 mW/cm2). It was noted that the PCE of the device based on DADP is almost double that of the device based on TPA-DCM-TPA, an analogue of DADP, although there is only a small difference between their molecular structures; DADP has a shorter distance between the triphenylamine (TPA) group and the 2-pyran-4-ylidenemalonitrile (PM) group ...

http://www.polymer.cn/UploadFile/research/200908281451155937.pdf

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Papers

Energy Level and Molecular Structure Engineering of Conjugated Donor−Acceptor Copolymers for Photovoltaic Applications

Synthesis and properties of polythiophene derivatives containing triphenylamine moiety and their photovoltaic applications

Solution-processable and thermal-stable triphenylamine-based dendrimers with truxene cores as hole-transporting materials for organic light-emitting devices

Synthesis of 4,7-Diphenyl-2,1,3-Benzothiadiazole-Based Copolymers and Their Photovoltaic Applications

Efficient Bulk-Heterojunction Solar Cells Based on a Symmetrical D-π-A-π-D Organic Dye Molecule