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Journal ArticleDOI

Solution-processed and high-performance organic solar cells using small molecules with a benzodithiophene unit.

28 May 2013-Journal of the American Chemical Society (J Am Chem Soc)-Vol. 135, Iss: 23, pp 8484-8487
TL;DR: The better PCEs were achieved by improving the short-circuit current density without sacrificing the high open-circuits voltage and fill factor through the strategy of incorporating the advantages of both conventional small molecules and polymers for OPVs.
Abstract: Three small molecules named DR3TBDTT, DR3TBDTT-HD, and DR3TBD2T with a benzo[1,2-b:4,5-b']dithiophene (BDT) unit as the central building block have been designed and synthesized for solution-processed bulk-heterojunction solar cells. Power conversion efficiencies (PCEs) of 8.12% (certified 7.61%) and 8.02% under AM 1.5G irradiation (100 mW cm(-2)) have been achieved for DR3TBDTT- and DR3TBDT2T-based organic photovoltaic devices (OPVs) with PC71BM as the acceptor, respectively. The better PCEs were achieved by improving the short-circuit current density without sacrificing the high open-circuit voltage and fill factor through the strategy of incorporating the advantages of both conventional small molecules and polymers for OPVs.
Citations
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Journal ArticleDOI
TL;DR: The results demonstrate that minimizing the alkyl chains to get suitable solubility and enhanced intermolecular packing has a great potential in further improving its photovoltaic performance.
Abstract: Optimizing the molecular structures of organic photovoltaic (OPV) materials is one of the most effective methods to boost power conversion efficiencies (PCEs). For an excellent molecular system with a certain conjugated skeleton, fine tuning the alky chains is of considerable significance to fully explore its photovoltaic potential. In this work, the optimization of alkyl chains is performed on a chlorinated nonfullerene acceptor (NFA) named BTP-4Cl-BO (a Y6 derivative) and very impressive photovoltaic parameters in OPV cells are obtained. To get more ordered intermolecular packing, the n-undecyl is shortened at the edge of BTP-eC11 to n-nonyl and n-heptyl. As a result, the NFAs of BTP-eC9 and BTP-eC7 are synthesized. The BTP-eC7 shows relatively poor solubility and thus limits its application in device fabrication. Fortunately, the BTP-eC9 possesses good solubility and, at the same time, enhanced electron transport property than BTP-eC11. Significantly, due to the simultaneously enhanced short-circuit current density and fill factor, the BTP-eC9-based single-junction OPV cells record a maximum PCE of 17.8% and get a certified value of 17.3%. These results demonstrate that minimizing the alkyl chains to get suitable solubility and enhanced intermolecular packing has a great potential in further improving its photovoltaic performance.

1,218 citations

Journal ArticleDOI
TL;DR: This review offered an overview of the organic photovoltaic materials based on BDT from the aspects of backbones, functional groups, alkyl chains, and device performance, trying to provide a guideline about the structure-performance relationship.
Abstract: Advances in the design and application of highly efficient conjugated polymers and small molecules over the past years have enabled the rapid progress in the development of organic photovoltaic (OPV) technology as a promising alternative to conventional solar cells. Among the numerous OPV materials, benzodithiophene (BDT)-based polymers and small molecules have come to the fore in achieving outstanding power conversion efficiency (PCE) and breaking 10% efficiency barrier in the single junction OPV devices. Remarkably, the OPV device featured by BDT-based polymer has recently demonstrated an impressive PCE of 11.21%, indicating the great potential of this class of materials in commercial photovoltaic applications. In this review, we offered an overview of the organic photovoltaic materials based on BDT from the aspects of backbones, functional groups, alkyl chains, and device performance, trying to provide a guideline about the structure-performance relationship. We believe more exciting BDT-based photovol...

942 citations

Journal ArticleDOI
TL;DR: In this article, a solution-processed small-molecule solar cells with almost 100% internal quantum efficiency and a power conversion efficiency of 9% were reported, making use of a donor molecule called DRCN7T and use PC71BM as an acceptor.
Abstract: Solution-processed small-molecule solar cells with almost 100% internal quantum efficiency and a power conversion efficiency of 9% are reported. The cells make use of a donor molecule called DRCN7T and use PC71BM as an acceptor.

764 citations

Journal ArticleDOI
TL;DR: A small molecule named DR3TSBDT with dialkylthiol-substituted benzo[1,2-b:4,5-b']dithiophene (BDT) as the central unit was designed and synthesized for solution-processed bulk-heterojunction solar cells.
Abstract: A small molecule named DR3TSBDT with dialkylthiol-substituted benzo[1,2-b:4,5-b′]dithiophene (BDT) as the central unit was designed and synthesized for solution-processed bulk-heterojunction solar cells. A notable power conversion efficiency of 9.95% (certified 9.938%) has been achieved under AM 1.5G irradiation (100 mW cm–2), with an average PCE of 9.60% based on 50 devices.

667 citations

Journal ArticleDOI
TL;DR: A model of the passivation mechanism is proposed to understand how the molecules simultaneously passivate the Pb-I antisite defects and vacancies created by under-coordinated Pb atoms, and how the energy offset between the semiconducting molecules and the perovskite influences trap states and intergrain carrier transport.
Abstract: The trap states at grain boundaries (GBs) within polycrystalline perovskite films deteriorate their optoelectronic properties, making GB engineering particularly important for stable high-performance optoelectronic devices. It is demonstrated that trap states within bulk films can be effectively passivated by semiconducting molecules with Lewis acid or base functional groups. The perovskite crystallization kinetics are studied using in situ synchrotron-based grazing-incidence X-ray scattering to explore the film formation mechanism. A model of the passivation mechanism is proposed to understand how the molecules simultaneously passivate the Pb-I antisite defects and vacancies created by under-coordinated Pb atoms. In addition, it also explains how the energy offset between the semiconducting molecules and the perovskite influences trap states and intergrain carrier transport. The superior optoelectronic properties are attained by optimizing the molecular passivation treatments. These benefits are translated into significant enhancements of the power conversion efficiencies to 19.3%, as well as improved environmental and thermal stability of solar cells. The passivated devices without encapsulation degrade only by ≈13% after 40 d of exposure in 50% relative humidity at room temperature, and only ≈10% after 24 h at 80 °C in controlled environment.

615 citations

References
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Journal ArticleDOI
TL;DR: Fluorene-Based Copolymers ContainingPhosphorescent Complexes and Carbazole-Based Conjugated Polymers R5.1.3.
Abstract: -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-

3,686 citations

Journal ArticleDOI
TL;DR: In this article, the authors showed that PFN can be incorporated into polymer light-emitting devices (PLEDs) to enhance electron injection from high-work-function metals such as aluminium (work function w of 4.3 eV) and gold (w ¼ 5.2 eV).
Abstract: typically based on n-type metal oxides, our device is solutionprocessed at room temperature, enabling easy processibility over a large area. Accordingly, the approach is fully amenable to highthroughput roll-to-roll manufacturing techniques, may be used to fabricate vacuum-deposition-free PSCs of large area, and find practical applications in future mass production. Moreover, our discovery overturns a well-accepted belief (the inferior performance of inverted PSCs) and clearly shows that the characteristics of high performance, improved stability and ease of use can be integrated into a single device, as long as the devices are optimized, both optically and electrically, by means of a meticulously designed device structure. We also anticipate that our findings will catalyse the development of new device structures and may move the efficiency of devices towards the goal of 10% for various material systems. Previously, we reported that PFN can be incorporated into polymer light-emitting devices (PLEDs) to enhance electron injection from high-work-function metals such as aluminium (work function w of 4.3 eV) 22,23 and has thus been used to realize high-efficiency, air-stable PLEDs 24 . Furthermore, we also found that efficient electron injection can be obtained even in the most noble metals with extremely high work functions, such as gold (w ¼ 5.2 eV), by lowering the effective work function (for example lowering w in gold by 1.0 eV), which has previously been ascribed to the formation of a strong interface dipole 25 .

3,651 citations

Journal ArticleDOI
TL;DR: Simultaneous enhancement of open-circuit voltage, short-circuits current density, and fill factor in highly efficient polymer solar cells by incorporating an alcohol/water-soluble conjugated polymer as cathode interlayer is domonstrated.
Abstract: Simultaneous enhancement of open-circuit voltage, short-circuit current density, and fill factor in highly efficient polymer solar cells by incorporating an alcohol/water-soluble conjugated polymer as cathode interlayer is domonstrated. When combined with a low-bandgap polymer PTB7 as the electron donor material, the power efficiency of the devices is improved to a certified 8.370%. Due to the drastic improvement in efficiency and easy utilization, this method opens new opportunities for PSCs from various material systems to improve towards 10% efficiency.

2,019 citations

Journal ArticleDOI
TL;DR: 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.
Abstract: 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.

1,649 citations

Journal ArticleDOI
TL;DR: This review summarizes the developments in small molecular donors, acceptors, and donor-acceptor dyad systems for high-performance multilayer, bulk heterojunction, and single-component OPVs and focuses on correlations of molecular chemical structures with properties, such as absorption, energy levels, charge mobilities, and photovoltaic performances.
Abstract: 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).

1,515 citations