7.7% Efficient All-Polymer Solar Cells Hwang, Ye-Jin; Courtright, Brett A. E.; Ferreira, Amy S. ...
Advanced materials (Weinheim),
August 19, 2015, Volume:
27, Issue:
31
Journal Article
Peer reviewed
By controlling the polymer/polymer blend self‐organization rate, all‐polymer solar cells composed of a high‐mobility, crystalline, naphthalene diimide‐selenophene copolymer acceptor and a ...benzodithiophene‐thieno3,4‐bthiophene copolymer donor are achieved with a record 7.7% power conversion efficiency and a record short‐circuit current density (18.8 mA cm−2).
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Design rules are presented for significantly expanding sequential processing (SqP) into previously inaccessible polymer:fullerene systems by tailoring binary solvent blends for fullerene deposition. ...Starting with a base solvent that has high fullerene solubility, 2‐chlorophenol (2‐CP), ellipsometry‐based swelling experiments are used to investigate different co‐solvents for the fullerene‐casting solution. By tuning the Flory‐Huggins χ parameter of the 2‐CP/co‐solvent blend, it is possible to optimally swell the polymer of interest for fullerene interdiffusion without dissolution of the polymer underlayer. In this way solar cell power conversion efficiencies are obtained for the PTB7 (poly(4,8‐bis(2‐ethylhexyl)oxybenzo1,2‐b:4,5‐b′dithiophene‐2,6‐diyl)(3‐fluoro‐2‐(2‐ethylhexyl)carbonylthieno3,4‐bthiophenediyl)) and PC61BM (phenyl‐C61‐butyric acid methyl ester) materials combination that match those of blend‐cast films. Both semicrystalline (e.g., P3HT (poly(3‐hexylthiophene‐2,5‐diyl)) and entirely amorphous (e.g., PSDTTT (poly(4,8‐di(2‐butyloxy)benzo1,2‐b:4,5‐b′dithiophene‐2,6‐diyl)‐alt‐(2,5‐bis(4,4′‐bis(2‐octyl)dithieno3,2‐b:2′3′‐dsilole‐2,6‐diyl)thiazolo5,4‐dthiazole)) conjugated polymers can be processed into highly efficient photovoltaic devices using the solvent‐blend SqP design rules. Grazing‐incidence wide‐angle x‐ray diffraction experiments confirm that proper choice of the fullerene casting co‐solvent yields well‐ordered interdispersed bulk heterojunction (BHJ) morphologies without the need for subsequent thermal annealing or the use of trace solvent additives (e.g., diiodooctane). The results open SqP to polymer/fullerene systems that are currently incompatible with traditional methods of device fabrication, and make BHJ morphology control a more tractable problem.
Sequential processing of polymers and fullerenes offers a new way to control the morphology of bulk‐heterojunction (BHJ) organic photovoltaics. The fullerene casting solvent must properly swell but not dissolve the polymer underlayer. A set of simple design rules is presented for finding the appropriate fullerene‐casting solvent blend to optimize BHJ formation and thus photovoltaic performance with any conjugated polymer.
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This cohort study examines the incidence of becoming homebound, being placed in a nursing home, and death in the US from 2012 to 2018 among Medicare beneficiaries aged 65 years and older.
OBJECTIVES
Care for older adults with dementia during the final years of life is costly, and families shoulder much of this burden. We aimed to assess the financial burden of care for those with and ...without dementia, and to explore differences across residential settings.
DESIGN
Using the Health and Retirement Study (HRS) and linked claims, we examined total healthcare spending and proportion by payer—Medicare, Medicaid, out‐of‐pocket, and calculated costs of informal caregiving—over the last 7 years of life, comparing those with and without dementia and stratifying by residential setting.
SETTING
The HRS is a nationally representative longitudinal study of older adults in the United States.
PARTICIPANTS
We sampled HRS decedents from 2004 to 2015. To ensure complete data, we limited the sample to those 72 years or older at death who had continuous fee‐for‐service Medicare Parts A and B coverage during the 7‐year period (n = 2909).
MEASUREMENTS
We compared decedents with dementia at last HRS assessment with those without dementia across annual and cumulative 7‐year spending measures, and personal characteristics. We present annual and cumulative spending by payer, and the changing proportion of spending by payer over time, comparing those with and without dementia and stratifying results by residential setting.
RESULTS
We found that, consistent with prior studies, people with dementia experience significantly higher costs, with a disproportionate share falling on patients and families. This pattern is most striking among community residents with dementia, whose families shoulder 64% of total expenditures (including $176,180 informal caregiving costs and $55,550 out‐of‐pocket costs), compared with 43% for people with dementia residing in nursing homes ($60,320 informal caregiving costs and $105,590 out‐of‐pocket costs).
CONCLUSION
These findings demonstrate disparities in financial burden shouldered by families of those with dementia, particularly among those residing in the community. They highlight the importance of considering the residential setting in research, programs, and policies. J Am Geriatr Soc 68:1319–1324, 2020.
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The efficiency of biological photosynthesis results from the exquisite organization of photoactive elements that promote rapid movement of charge carriers out of a critical recombination range. If ...synthetic organic photovoltaic materials could mimic this assembly, charge separation and collection could be markedly enhanced. We show that micelle-forming cationic semiconducting polymers can coassemble in water with cationic fullerene derivatives to create photoinduced electron-transfer cascades that lead to exceptionally long-lived polarons. The stability of the polarons depends on the organization of the polymer-fullerene assembly. Properly designed assemblies can produce separated polaronic charges that are stable for days or weeks in aqueous solution.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
Although most polymer/fullerene-based solar cells are cast from a blend of the components in solution, it is also possible to sequentially process the polymer and fullerene layers from ...quasi-orthogonal solvents. Sequential processing (SqP) not only produces photovoltaic devices with efficiencies comparable to the more traditional bulk heterojunction (BHJ) solar cells produced by blend casting (BC) but also offers the advantage that the polymer and fullerene layers can be optimized separately. In this paper, we explore the morphology produced when sequentially processing polymer/fullerene solar cells and compare it to the BC morphology. We find that increasing polymer regioregularity leads to the opposite effect in SqP and BC BHJ solar cells. We start by constructing a series of SqP and BC solar cells using different types of poly(3-hexylthiophene) (P3HT) that vary in regioregulary and polydispersity combined with 6,6-phenyl-C61-butyric-acid-methyl-ester (PCBM). We use grazing incidence wide-angle X-ray scattering to demonstrate how strongly changes in the P3HT and PCBM crystallinity upon thermal annealing of SqP and BC BHJ films depend on polymer regioregularity. For SqP devices, low regioregularity P3HT films that possess more amorphous regions allow for more PCBM crystallite growth and thus show better photovoltaic device efficiency. On the other hand, highly regioregular P3HT leads to a more favorable morphology and better device efficiency for BC BHJ films. Comparing the photovoltaic performance and structural characterization indicates that the mechanisms controlling morphology in the active layers are fundamentally different for BHJs formed via SqP and BC. Most importantly, we find that nanoscale morphology in both SqP and BC BHJs can be systematically controlled by tuning the amorphous fraction of polymer in the active layer.
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IJS, KILJ, NUK, PNG, UL, UM
•Approaches to the fractionation of starch hydrolysis products (SHP) are described.•Fractionations were based on differential solubility in 50–95% aqueous ethanol.•The molecular dispersity of ...representative SHP fractions is presented.•Chemical and spectroscopic analyses of representative SHP fractions are presented.•A simple method for obtaining refined food-grade SHP preparations is outlined.
Considerable research is focused on understanding the functionality of starch hydrolysis products (SHP) consisting of glucose, maltose, maltooligosaccharides (MOS), and maltopolysaccharides (MPS). A confounding factor in this research is the high molecular dispersity of commercially available SHP. The study presented herein characterizes a flexible fractionation approach for lowering the dispersity of such products. This was accomplished by fractionating a corn syrup solids (CSS) preparation based on the differential solubility of its component saccharides in aqueous-ethanol solutions. Products obtained from selected fractionations were characterized with respect to degree of polymerization (DP; liquid chromatography), dextrose equivalency (reducing sugar assays), and prevalence of branching (NMR). Glucose and maltose were preferentially removed from CSS using high (⩾90%) ethanol extractants. Preparations with relatively narrow ranges of MOS, lower DP MPS, and higher DP MPS were obtained through repetitive 70%-ethanol extractions. Linear, as opposed to branched, MOS and MPS were preferentially extracted under all conditions tested.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Polymer:fullerene bulk heterojunction (BHJ) solar cell active layers can be created by traditional blend casting (BC), where the components are mixed together in solution before deposition, or by ...sequential processing (SqP), where the pure polymer and fullerene materials are cast sequentially from different solutions. Presently, however, the relative merits of SqP as compared to BC are not fully understood because there has yet to be an equivalent (composition- and thickness-matched layer) comparison between the two processing techniques. The main reason why matched SqP and BC devices have not been compared is because the composition of SqP active layers has not been accurately known. In this paper, we present a novel technique for accurately measuring the polymer:fullerene film composition in SqP active layers, which allows us to make the first comparisons between rigorously composition- and thickness-matched BHJ organic solar cells made by SqP and traditional BC. We discover that, in optimal photovoltaic devices, SqP active layers have a very similar composition as their optimized BC counterparts (≈44–50 mass % PCBM). We then present a thorough investigation of the morphological and device properties of thickness- and composition-matched P3HT:PCBM SqP and BC active layers in order to better understand the advantages and drawbacks of both processing approaches. For our matched devices, we find that small-area SqP cells perform better than BC cells due to both superior film quality and enhanced optical absorption from more crystalline P3HT. The enhanced film quality of SqP active layers also results in higher performance and significantly better reproducibility in larger-area devices, indicating that SqP is more amenable to scaling than the traditional BC approach. X-ray diffraction, UV–vis absorption, and energy-filtered transmission electron tomography collectively show that annealed SqP active layers have a finer-scale blend morphology and more crystalline polymer and fullerene domains when compared to equivalently processed BC active layers. Charge extraction by linearly increasing voltage (CELIV) measurements, combined with X-ray photoelectron spectroscopy, also show that the top (nonsubstrate) interface for SqP films is slightly richer in PCBM compared to matched BC active layers. Despite these clear differences in bulk and vertical morphology, transient photovoltage, transient photocurrent, and subgap external quantum efficiency measurements all indicate that the interfacial electronic processes occurring at P3HT:PCBM heterojunctions are essentially identical in matched-annealed SqP and BC active layers, suggesting that device physics are surprisingly robust with respect to the details of the BHJ morphology.
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IJS, KILJ, NUK, PNG, UL, UM
Identifying the seriously ill population is integral to improving the value of health care. Efforts to identify this population using existing data are anchored to a list of severe medical conditions ...(SMCs) using diagnostic codes. Published approaches have used International Classification of Diseases, Ninth Revision (ICD-9) codes, which has since been replaced by ICD-10.
We translated SMCs from ICD-9 to ICD-10 using a refined code list. We aimed to test the hypothesis that people identified by ICD-9 or ICD-10 codes would have similar Medicare costs, health care utilization, and mortality.
Using data from the National Health and Aging Trends Study linked to Medicare claims, we compared samples from periods using ICD-9 (2014) and ICD-10 (2016). We included participants with six-month fee-for-service Medicare data before their interview date who had an SMC identified within that period. We compared the groups' demographic, functional, and medical characteristics and followed up them for six months to compare outcomes.
Among subjects in the 2016 (ICD-10) sample, 19.9% were hospitalized, 24.6% used the emergency department, 7.2% died, and average Medicare spending totaled $9902.04 over six months of follow-up. We observed no significant differences between the 2014 and 2016 samples (P > 0.05); both samples represent 18% of Medicare fee-for-service beneficiaries.
Identifying the seriously ill population using currently available data requires using ICD-10 to define SMCs. Routine measurement of function, quality of life, and caregiver strain will further enhance the identification process and efficiently target palliative care services and appropriate quality measures.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
IMPORTANCE
A large and growing population of older adults with multimorbidity, cognitive impairment, and functional disability live in the community, but many never or rarely leave their homes. Being ...homebound is associated with decreased access to medical services, poor health outcomes, and increased mortality. Yet, it is unknown what factors, in particular socioeconomic factors, are associated with new onset of homebound status.
OBJECTIVE
To evaluate the association between income and risk of becoming homebound.
DESIGN
Observational cohort study using 2011 to 2018 data from the National Health and Aging Trends Study, a nationally representative sample of Medicare beneficiaries aged 65 years and older.
SETTING
Population‐based study in the United States.
PARTICIPANTS
A total of 7,042 initially nonhomebound community‐dwelling older adults.
EXPOSURE
Total annual household income at baseline (in 2011) measured via self‐report.
OUTCOME
Annual measure of homebound status, defined as leaving home an average of 1 d/wk or less.
RESULTS
Over 7 years, 15.81% of older adults in the lowest income quartile (≤$15,003) became homebound, compared with only 4.64% of those in the highest income quartile (>$60,000). In a competing risks analysis accounting for risks of death and nursing home admission, and adjusted for clinical and demographic characteristics, those in the lowest income quartile had a substantially higher subhazard of becoming homebound than those in the highest income quartile (1.65; 95% confidence interval = 1.20–2.29). Moreover, we see evidence of a gradient in risk of homebound status by income quartile.
CONCLUSION AND RELEVANCE
Our work demonstrates that financial resources shape the risk of becoming homebound, which is associated with negative health consequences. In the context of existing income disparities, more support is needed to assist older adults with limited financial resources who wish to remain in the community.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
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