Water/Ethanol Soluble p-Type Conjugated Polymers for the Use in Organic Photovoltaics

We have developed two series of p-type conjugated polymers based on poly[2,3-bis-(3-octyloxyphenyl)quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl] (TQ1) polymeric backbone utilizing polar pendant groups, i.e., tertiary amine and pyridine, to achieve switchable solubility in water and ethanol. By balancing the ratio between polar and non-polar side-groups, we could combine green-solvent processability with the manufacturing of functional photovoltaic devices. Due to the unavailability of water/alcohol soluble acceptors, the photovoltaic performance of these new polymers was evaluated using organic solvent by incorporating PC61BM. For water/alcohol soluble partial amine-based polymers, we achieve a maximum power conversion efficiency (PCE) of ∼0.8% whereas alcohol soluble partial pyridine-based polymers show enhanced PCE of ∼1.3% with inverted device structure. We propose that the enhancement in PCE is a result of the reduction in amino-group content and the lower basicity of pyridine, both of which decrease the interaction between functionalized polymers with the anode interface material and reduce the miscibility of the donor and acceptor. Further improvement of the photovoltaic performance, in particular the open-circuit voltage (Voc), was achieved by using an anode buffer layer to mitigate the unfavorable interaction of the amino/pyridine groups with the MoO3 electrode. Our work demonstrated the possibility of substituent modification for conjugated polymers using tertiary amine and pyridine groups to achieve water/alcohol soluble and functional donor materials

A Facile Method to Enhance Photovoltaic Performance of Benzodithiophene-Isoindigo Polymers by Inserting Bithiophene Spacer

This study describes the synthesis and characterization of four polymers based on benzo[1,2-b:4,5-b']dithiophene (BDT) and isoindigo with zero, one, two, and three thiophene spacer groups. Results have demonstrated that the use of bithiophene as a spacer unit improves the geometry of the polymer chain, making it planar, and hence, potentially enhanced π- π stacking occurs. Due to favorable interaction of the polymer chains, enhanced absorption coefficient, and optimal morphology, PBDT-BTI, which possesses bithiophene as a spacer, revealed high current and fill factor leading to a power conversion efficiency of 7.3% in devices, making this polymer the best performing isoindigo-based material in polymer solar cells (PSCs). Also, PBDT-BTI could still maintain efficiency of over 6% with the active layer thickness of 270 nm, making it a potential candidate for a material in printed PSCs. These results demonstrate that the use of thiophene spacers in D-A polymers could be an important design strategy to produce high-performance PSCs

Global, regional, and national cancer incidence, mortality, years of life lost, years lived with disability, and disability-Adjusted life-years for 29 cancer groups, 1990 to 2017 : A systematic analysis for the global burden of disease study

Importance: Cancer and other noncommunicable diseases (NCDs) are now widely recognized as a threat to global development. The latest United Nations high-level meeting on NCDs reaffirmed this observation and also highlighted the slow progress in meeting the 2011 Political Declaration on the Prevention and Control of Noncommunicable Diseases and the third Sustainable Development Goal. Lack of situational analyses, priority setting, and budgeting have been identified as major obstacles in achieving these goals. All of these have in common that they require information on the local cancer epidemiology. The Global Burden of Disease (GBD) study is uniquely poised to provide these crucial data. Objective: To describe cancer burden for 29 cancer groups in 195 countries from 1990 through 2017 to provide data needed for cancer control planning. Evidence Review: We used the GBD study estimation methods to describe cancer incidence, mortality, years lived with disability, years of life lost, and disability-Adjusted life-years (DALYs). Results are presented at the national level as well as by Socio-demographic Index (SDI), a composite indicator of income, educational attainment, and total fertility rate. We also analyzed the influence of the epidemiological vs the demographic transition on cancer incidence. Findings: In 2017, there were 24.5 million incident cancer cases worldwide (16.8 million without nonmelanoma skin cancer [NMSC]) and 9.6 million cancer deaths. The majority of cancer DALYs came from years of life lost (97%), and only 3% came from years lived with disability. The odds of developing cancer were the lowest in the low SDI quintile (1 in 7) and the highest in the high SDI quintile (1 in 2) for both sexes. In 2017, the most common incident cancers in men were NMSC (4.3 million incident cases); tracheal, bronchus, and lung (TBL) cancer (1.5 million incident cases); and prostate cancer (1.3 million incident cases). The most common causes of cancer deaths and DALYs for men were TBL cancer (1.3 million deaths and 28.4 million DALYs), liver cancer (572000 deaths and 15.2 million DALYs), and stomach cancer (542000 deaths and 12.2 million DALYs). For women in 2017, the most common incident cancers were NMSC (3.3 million incident cases), breast cancer (1.9 million incident cases), and colorectal cancer (819000 incident cases). The leading causes of cancer deaths and DALYs for women were breast cancer (601000 deaths and 17.4 million DALYs), TBL cancer (596000 deaths and 12.6 million DALYs), and colorectal cancer (414000 deaths and 8.3 million DALYs). Conclusions and Relevance: The national epidemiological profiles of cancer burden in the GBD study show large heterogeneities, which are a reflection of different exposures to risk factors, economic settings, lifestyles, and access to care and screening. The GBD study can be used by policy makers and other stakeholders to develop and improve national and local cancer control in order to achieve the global targets and improve equity in cancer care. © 2019 American Medical Association. All rights reserved.Peer reviewe

Synthesis of Conjugated Polymers for Solar Cell Applications

Fossil fuels are largely used as a source of energy to fulfil the energy demand of mankind. However, fossil fuels suffer from limitations. The unlimited burning of fossil fuels releases greenhouse gases and causes environmental pollution. Fossil fuels are also an unreliable source of energy since the natural deposit is limited. Therefore, a clean and reliable source of energy is highly demanded. Direct conversion of the solar energy into electrical energy by solar cell technology is clean and desired. Inorganic materials like silicon are still the most widely used for making solar cell devices. Preparation of large area devices from inorganic materials, however, is not easy and therefore it is not possible to produce very cheap solar cells. In 1977, it was observed for the first time that conjugated polymers can conduct electricity. Following this break through discovery, many conjugated polymers were synthesised and characterised for optoelectronic application.In this study, three polymers namely APFO-Black 1, APFO-Black 2 and APFO-25 were synthesised and characterised. The synthesis of the polymers started from simple commercially available materials and the corresponding monomers were built in a step-by-step fashion. The respective monomers were joined to a functionalized fluorene unit by Suzuki coupling methodology. The black polymers showed wider optical absorption and a better match with the emission spectrum of the sun compared to most conjugated polymers. The best device efficiency obtained from APFO-Black 1 was 1.15% while APFO-Black 2 showed an efficiency of 1.49%. APFO-25 on the other hand consists of a polar group to get an improved miscibility and also to get stable nano-morphology of the donor-acceptor blend in bulk heterojunction solar cell device. APFO-25 showed a decent efficiency reaching 2.8%

Synthesis of Conjugated Polymers for Solar Cell Applications

Fossil fuels are largely used as a source of energy to fulfil the energy demand of mankind. However, fossil fuels suffer from limitations. The unlimited burning of fossil fuels releases greenhouse gases and causes environmental pollution. Fossil fuels are also an unreliable source of energy since the natural deposit is limited. Therefore, a clean and reliable source of energy is highly demanded. Direct conversion of the solar energy into electrical energy by solar cell technology is clean and desired. Inorganic materials like silicon are still the most widely used for making solar cell devices. Preparation of large area devices from inorganic materials, however, is not easy and therefore it is not possible to produce very cheap solar cells. In 1977, it was observed for the first time that conjugated polymers can conduct electricity. Following this break through discovery, many conjugated polymers were synthesised and characterised for optoelectronic application.In this study, three polymers namely APFO-Black 1, APFO-Black 2 and APFO-25 were synthesised and characterised. The synthesis of the polymers started from simple commercially available materials and the corresponding monomers were built in a step-by-step fashion. The respective monomers were joined to a functionalized fluorene unit by Suzuki coupling methodology. The black polymers showed wider optical absorption and a better match with the emission spectrum of the sun compared to most conjugated polymers. The best device efficiency obtained from APFO-Black 1 was 1.15% while APFO-Black 2 showed an efficiency of 1.49%. APFO-25 on the other hand consists of a polar group to get an improved miscibility and also to get stable nano-morphology of the donor-acceptor blend in bulk heterojunction solar cell device. APFO-25 showed a decent efficiency reaching 2.8%

Donor - acceptor polymers for organic Photovoltaics

Semiconducting organic conjugated polymers are characterized by a backbone chain of alternating double- and single-bonds, which are commonly used as photoactive materials in photovoltaic devices. One of the most widely studied design methodologies for the synthesis of conjugated polymers is the donor-acceptor approach in which the backbones of the polymers are built from covalently bonded electron rich and electron poor aromatic units assembled together via transition metal-catalyzed cross-coupling reactions. This chapter is devoted to give an overview on the progresses made in the design and synthesis of donor-acceptor conjugated polymers and discuss their optical, electrochemical, and photovoltaic characteristics. The structure-property correlations of the polymers, prepared by the different transition metal-catalyzed cross-coupling reactions are also discussed

Optimizing Polymer Solar Cells Using Non-Halogenated Solvent Blends

More environmentally friendly polymer solar cells were constructed using a conjugated polymer, poly (2,5-thiophene-alt-4,9-bis(2-hexyldecyl)-4,9-dihydrodithieno[3,2-c:3′,2′h][1,5] naphthyridine-5,10-dione, PTNT, as a donor material in combination with PC71BM as an acceptor in a bulk heterojunction device structure. A non-halogenated processing solvent (o-xylene) and solvent additives that are less harmful to the environment such as 1-methoxynaphthalene (MN) and 1-phenylnaphthalene (PN) were used throughout the study as processing solvents. The most widely used halogenated solvent additives (1,8-diiodooctane (DIO) and 1-chloronaphthalene (CN)) were also used for comparison and to understand the effect of the type of solvent additives on the photovoltaic performances. Atomic force microscopy (AFM) was employed to investigate the surface morphology of the films prepared in the presence of the various additives. The best-performing polymer solar cells provided a high open-circuit voltage of 0.9 V, an efficient fill factor of around 70%, and a highest power conversion efficiency (PCE) of over 6% with the use of the eco-friendlier o-xylene/MN solvent systems. Interestingly, the solvent blend which is less harmful and with low environmental impact gave a 20% rise in PCE as compared to an earlier reported device efficiency that was processed from the chlorinated solvent o-dichlorobenzene (o-DCB)

Recent Advances in the Synthesis of Electron Donor Conjugated Terpolymers for Solar Cell Applications

The synthesis of donor (D)-acceptor (A) polymers using structurally elaborated monomers is an active research field. Some of the challenges with the use of alternating D-A polymers for photovoltaic applications are the relatively narrow absorption widths, the presence an absorption valleys in the visible region, unoptimized molecular energy levels and even lack of compatibility of the polymers with the common acceptors. The synthesis and characterization of polymers consisting of multiple chromophores (random and regular terpolymers) with complementing properties is currently gaining momentum in order to delicately optimize properties of polymers. A random terpolymer can either be of a system composed of one donor and two acceptors [(D-A1)-ran-(D-A2)] or a one acceptor and two donor segments [(D1-A)-ran-(D2-A)] incorporated in the polymer backbone. By varying the composition of the monomers in the feed of the polymerization reaction, the properties of the resulting terpolymers can be carefully optimized. Using this strategy, many materials with desired properties have been developed and power conversion efficiency (PCE) surpassing 14% in a single layer bulk heterojunction (BHJ) solar cell device have been reported. This review summarizes the most recent advances made in the development of electron donor terpolymers for organic photovoltaics (OPVs). The properties of the terpolymers are compared with their respective reference polymer