Trap-state suppression and improved charge transport in PbS quantum dot solar cells with synergistic mixed ligand treatments

The power conversion efficiency of colloidal PbS‐quantum‐dot (QD)‐based solar cells is significantly hampered by lower‐than‐expected open circuit voltage (VOC). The VOC deficit is considerably higher in QD‐based solar cells compared to other types of existing solar cells due to in‐gap trap‐induced bulk recombination of photogenerated carriers. Here, this study reports a ligand exchange procedure based on a mixture of zinc iodide and 3‐mercaptopropyonic acid to reduce the VOC deficit without compromising the high current density. This layer‐by‐layer solid state ligand exchange treatment enhances the photovoltaic performance from 6.62 to 9.92% with a significant improvement in VOC from 0.58 to 0.66 V. This study further employs optoelectronic characterization, X‐ray photoelectron spectroscopy, and photoluminescence spectroscopy to understand the origin of VOC improvement. The mixed‐ligand treatment reduces the sub‐bandgap traps and significantly reduces bulk recombination in the devices.Peer ReviewedPostprint (author's final draft

Colloidal Quantum Dot Tandem Solar Cells Using CVD Graphene as An Atomically Thin Intermediate Recombination Layer

Two-terminal tandem cell architectures are believed to be an effective way to further improve the power conversion efficiency in solution processed photovoltaics. To design an efficient tandem solar cell, two key issues need to be considered. First, subcells with well-matched currents and complementary absorption characteristics are a prerequisite for high efficiency. Second, identifying the appropriate intermediate layer (IML) to connect the subcells is necessary to minimize the optical and electronic losses. PbS colloidal quantum dots (CQDs) are a notable choice for the subcells due to their low cost, solution processability, and remarkable wide range band gap tunability. Single-layer graphene (Gr) has been proposed to be a promising IML due to its high transparency and conductivity. Here, as a proof of concept, we demonstrate a solution-processed, two-terminal PbS CQDs tandem solar cell employing chemical vapor deposited Gr as the IML. In doing so, we report a PbS CQD cell comprising subcells with bandgaps of 1.4 and 0.95 eV that delivers power conversion efficiency in excess of 7%, substantially higher than that of previously reported CQD tandem cells.Peer ReviewedPostprint (author's final draft

Barriers and Delays in Tuberculosis Diagnosis and Treatment Services: Does Gender Matter?

Background:. Tuberculosis (TB) remains a global public health problem with known gender-related disparities. We reviewed the quantitative evidence for gender-related differences in accessing TB services from symptom onset to treatment initiation. Methods:. Following a systematic review process, we: searched 12 electronic databases; included quantitative studies assessing gender differences in accessing TB diagnostic and treatment services; abstracted data; and assessed study validity. We defined barriers and delays at the individual and provider/system levels using a conceptual framework of the TB care continuum and examined gender-related differences. Results:. Among 13,448 articles, 137 were included: many assessed individual-level barriers (52%) and delays (42%), 76% surveyed persons presenting for care with diagnosed or suspected TB, 24% surveyed community members, and two-thirds were from African and Asian regions. Many studies reported no gender differences. Among studies reporting disparities, women faced greater barriers (financial: 64% versus 36%; physical: 100% versus 0%; stigma: 85% versus 15%; health literacy: 67% versus 33%; and provider-/system-level: 100% versus 0%) and longer delays (presentation to diagnosis: 45% versus 0%) than men. Conclusions:. Many studies found no quantitative gender-related differences in barriers and delays limiting access to TB services. When differences were identified, women experienced greater barriers and longer delays than men

Contributions for a Community Good: Results from a Field Experiment in India

This paper presents the results of a field experiment on voluntary contribution for a proposed community good. The experiment was conducted at village Sundarika, District South 24 parganas, in West Bengal, India. The proposed community good was a community medicinal plant garden. Solicitation letters, on behalf of a local Community Based Organization (CBO), were delivered to one hundred households by the experimenters with the request to contribute generously for the proposed garden. Sixty-five households contributed and a strong positive association is found between contributions and CBO membership on the one hand and landholding on the other

Electroweak box diagrams on the lattice for pion and neutron decay

CKM matrix is unitary by construction in the standard model(SM). The recent analyses on the first row of CKM matrix show $\approx 3\sigma$ tension with unitarity. Nonperturbative calculations of the radiative corrections can reduce the theory uncertainty in CKM matrix elements. Here we compute the electroweak box contribution to the pion and kaon $\beta$ decays using seven $N_f=2+1+1$ HISQ-Clover lattice with various pion mass and lattice spacing. The continuum and chiral limit is taken using the leading dependence on $M_\pi$ and $a$, where $M_\pi$ extrapolation is taken to the physical pion mass and $SU(3)$ symmetric mass for pion and kaon box contribution, respectively. Our results are $\square_{\gamma W}^{VA} |_{\pi} = 2.820 (28) \times 10^{-3}$ and $\square_{\gamma W}^{VA} |_{K} = 2.384 (17) \times 10^{-3}$.Comment: 9 pages, 7 figures, Lattice 202

Pectoralis major myocutaneous flap in head and neck reconstruction: an interesting experience from central India regional cancer center

Background: Head and neck cancer are sixth most common cancers worldwide with cancer of oral cavity most common. The primary treatment modality for oral cavity cancer has been surgery and defects resulting from the ablation of the tumors require reconstruction. the PMMC flap offer an easy, less time consuming with minimal postoperative complication as a reconstructive option in the hands of reconstructive surgeon. The objective of our study was to give a precise description of our experience with the PMMC flap as a reconstructive option in post-ablative head and cancer surgery.Methods: The current prospective study was conducted in the Department of Surgical Oncology, Regional cancer center, Pt. JNMC, Raipur (C.G.), India from the January 2014 to June 2015. Detailed clinical history and examination of the patients were recorded. All Investigations relevant to the study were done before the surgical procedure. Procedure was performed as per standard protocol and reconstruction was made with PMMC flap. Data was compiled in MS Excel and checked for its completeness and correctness. Then it was analyzed.Results: In the present study male to female ratio was 2:1. Most of the patients belongs to the age group of 41-60 (55.55%) followed by 21-40 (30.15%). In the present study majority of patient of oral malignancy presented with lower alveolus malignancy (36.5%) followed by buccal mucosa malignancy (19.06%).Conclusions: Pectoralis major myocutaneous flap was found to be a versatile flap for reconstruction of large defects in Head and Neck region with minimal complication rate.