The photophysics of solution processable semiconductors for applications in optoelectronic devices

A large amount of the demand for energy worldwide is for electricity which in turn goes towards domestic uses, powering electronic devices, communication, lighting, et cetera. Solar energy has thus gained much attention over the past few decades as a clean, renewable and well-distributed source of energy globally. Although Silicon solar cells remain the most purchased solar cells these past few decades and currently have module-scale efficiencies exceeding 20%; emerging solar cell technologies (based on materials such as organic polymers, quantum dots and perovskites) have become increasingly popular and continuously challenge the dominance of Silicon. This is especially true for niche applications where their flexibility, semi-transparency, and range of colours give them advantages over Silicon. In particular, they can be cheaply synthesised and coated into ultrathin layers which makes them ideal for technologies such as disposable electronics, sensors, semi-transparent barriers, and wearables, among others. This thesis presents the results of experiments on these emerging solution-processable optoelectronic materials. The experiments described herein address methodologies such as the use of additives to improve the dielectric constant of organic photovoltaic blends, the related strategy of using the intrinsic dipolar alignment of a ferroelectric polymer to enhance the efficiency of polymer solar cells, as well as topics regarding hybrid organic-inorganic perovskites - such as the light-soaking effect in perovskite solar cells, and the photophysical properties of perovskite-shelled Lead Sulphide quantum dots. The final results improve our understanding of these classes of solution-processable semiconductors and point towards avenues for further material improvements

Interfacial Morphology Addresses Performance of Perovskite Solar Cells Based on Composite Hole Transporting Materials of Functionalized Reduced Graphene Oxide and P3HT

The development of novel hole transporting materials (HTMs) for perovskite solar cells (PSCs) that can enhance device's reproducibility is a largely pursued goal, even to the detriment of a very high efficiency, since it paves the way to an effective industrialization of this technology. In this work, we study the covalent functionalization of reduced graphene oxide (RGO) flakes with different organic functional groups with the aim of increasing the stability and homogeneity of their dispersion within a poly(3-hexylthiophene) (P3HT) HTM. The selected functional groups are indeed those recalling the two characteristic moieties present in P3HT, i.e., the thienyl and alkyl residues. After preparation and characterization of a number of functionalized RGO@P3HT blends, we test the two containing the highest percentage of dispersed RGO as HTMs in PSCs and compare their performance with that of pristine P3HT and of the standard Spiro-OMeTAD HTM. Results reveal the big influence of the morphology adopted by the single RGO flakes contained in the composite HTM in driving the final device performance and allow to distinguish one of these blends as a promising material for the fabrication of highly reproducible PSCs

On Lowering the Error Floor of Short-to-Medium Block Length Irregular Low Density Parity Check Codes

Edited version embargoed until 22.03.2019 Full version: Access restricted permanently due to 3rd party copyright restrictions. Restriction set on 22.03.2018 by SE, Doctoral CollegeGallager proposed and developed low density parity check (LDPC) codes in the early 1960s. LDPC codes were rediscovered in the early 1990s and shown to be capacity approaching over the additive white Gaussian noise (AWGN) channel. Subsequently, density evolution (DE) optimized symbol node degree distributions were used to significantly improve the decoding performance of short to medium length irregular LDPC codes. Currently, the short to medium length LDPC codes with the lowest error floor are DE optimized irregular LDPC codes constructed using progressive edge growth (PEG) algorithm modifications which are designed to increase the approximate cycle extrinsic message degrees (ACE) in the LDPC code graphs constructed. The aim of the present work is to find efficient means to improve on the error floor performance published for short to medium length irregular LDPC codes over AWGN channels in the literature. An efficient algorithm for determining the girth and ACE distributions in short to medium length LDPC code Tanner graphs has been proposed. A cyclic PEG (CPEG) algorithm which uses an edge connections sequence that results in LDPC codes with improved girth and ACE distributions is presented. LDPC codes with DE optimized/’good’ degree distributions which have larger minimum distances and stopping distances than previously published for LDPC codes of similar length and rate have been found. It is shown that increasing the minimum distance of LDPC codes lowers their error floor performance over AWGN channels; however, there are threshold minimum distances values above which there is no further lowering of the error floor performance. A minimum local girth (edge skipping) (MLG (ES)) PEG algorithm is presented; the algorithm controls the minimum local girth (global girth) connected in the Tanner graphs of LDPC codes constructed by forfeiting some edge connections. A technique for constructing optimal low correlated edge density (OED) LDPC codes based on modified DE optimized symbol node degree distributions and the MLG (ES) PEG algorithm modification is presented. OED rate-½ (n, k)=(512, 256) LDPC codes have been shown to have lower error floor over the AWGN channel than previously published for LDPC codes of similar length and rate. Similarly, consequent to an improved symbol node degree distribution, rate ½ (n, k)=(1024, 512) LDPC codes have been shown to have lower error floor over the AWGN channel than previously published for LDPC codes of similar length and rate. An improved BP/SPA (IBP/SPA) decoder, obtained by making two simple modifications to the standard BP/SPA decoder, has been shown to result in an unprecedented generalized improvement in the performance of short to medium length irregular LDPC codes under iterative message passing decoding. The superiority of the Slepian Wolf distributed source coding model over other distributed source coding models based on LDPC codes has been shown

Pediatric suspension usage & reconstitution practices of mothers in Zaria, northwestern Nigeria

Background: Dry powders for suspension are a common type of drug formulation used for children. Studies have shown that mothers and/other caregivers often have difficulties correctly reconstituting these powders, and accurately measuring out doses.Objectives: To describe the pediatric suspension usage practices, reconstitution techniques and medication related knowledge of mothers attending the antenatal clinic of Ahmadu Bello University Medical Center, Zaria, Kaduna state.Methods: A data collection instrument was used to interview 101 conveniently sampled women in October 2018. After answering the questions in three sections of the instrument, respondents were given a bottle of water and a medicine bottle containing flour. They were then asked to show the researchers how they would normally reconstitute a suspension, and asked to measure out specific doses using a measuring cup.Results: Almost 40% of mothers stored reconstituted medication in the fridge, and less than 20% would administer a forgotten dose when they remembered and continue with the previous dosing times. Regarding reconstitution techniques, 26.7% of mothers initially shook the bottle to loosen the dry powder before adding water, and 39.6% added water in two steps. Less than 10% of respondents could correctly measure 7.5 mL using a measuring cup. Over 40% of them could not accurately calculate medication dosing times in the hypothetical scenario provided to assess their medication related knowledge.Conclusion: The results show that some of the usage practices and reconstitution techniques of the mothers were sub-optimal. Pharmacists can help mothers reconstitute suspensions as part of their pharmaceutical care responsibilities.Keywords: Mothers, Nigeria, Pediatric suspensions, Reconstitution techniqu

Perceptions of undergraduate pharmacy students of Ahmadu Bello University Zaria, Nigeria on the introduction of the Pharm.D. degree to Nigerian pharmacy schools

As a result of the increasing scope of Pharmacy practice over the years, many countries (Nigeria inclusive) are introducing or undertaking major transformations in pharmacy education. The main aim of this work is to explore the knowledge and perceptions of selected 4th and 5th year undergraduate students of Ahmadu Bello University, Zaria on the introduction of the proposed Pharm. D. Degree to Nigerian pharmacy schools. The study was qualitative, and used focus group discussions (FGDs) to collect data. Two focus group discussions with ten students (Five participants per group), lasting an average of one hour were audiotaped in June 2017. Data obtained from the FGDs was then transcribed and checked for accuracy and the transcripts analyzed using summative qualitative content analysis. Most participants highlighted both advantages and disadvantages to introducing the new degree. Advantages identified included the potential for specialization and better career prospects. On the other hand, they expressed worries that the degree change would be disadvantageous to people interested in other (non-clinical) areas of pharmacy practice. Several participants also felt that the degree change was going to be unsuccessful because of several factors within our environment including the unharmonious working relationship between healthcare professionals, inadequate infrastructure in pharmacy schools and the unwillingness of several lecturers to embrace the new degree. In conclusion, participants believed that the proposed Pharm.D. Degree was both potentially advantageous and problematic. Their recommendations include increasing the awareness of both staff and prospective students on what the degree entailed, and allowing concurrent coexistence of both B.Pharm and Pharm.D. DegreesKeywords: Focus group, Curriculum change, Students, Nigeria, Pharm.D., Perceptions

Perceived Stress Levels and Stressors in Undergraduate Pharmacy Students’ at a Nigerian Tertiary Institution

Background: While everyone can be affected by stress, there is evidence to suggest that students might be more prone.Objective: To assess perceived stress levels and well-being among undergraduate pharmacy students’ of Ahmadu Bello University, in addition to identifying common stressors and coping mechanisms used by the students.Methods: A survey was conducted on second to fifth year undergraduate pharmacy students of the institution from August to November 2019. A self-administered questionnaire was used to collect data about the students’ socio-demographic characteristics, stress levels (Perceived Stress Scale-10), well-being (World Health Organization-5 well-being index), stressors and coping strategies. Student t-tests, analysis of variance (ANOVA) and Pearson’s bivariate correlation were used to compare means and correlations between variables. P < 0.05 was considered as statistically significant.Results: Of the 350-questionnaire distributed, 328 were returned producing a 93.7% response rate. Majority of respondents were males (63.1%), and in their third year of study (29.3%). The mean PSS-10 score was 18.4 ± 4.9, and a statistically significant difference in scores were seen across gender (p= 0.001). Over half of the participants (72.8%) also scored 51% or higher on the WHO-5 index. Their most common stressors were volume of course materials 184 (56.1%) and financial constraints 158 (48.2%) respectively. More than half of respondents (64.5%) also sought for emotional support from their families to cope with stress. A statistically significant (p<0.001) negative weak correlation (-0.3) was seen when PSS-10 and WHO-5 scores were compared.Conclusion: Perceived stress levels in female undergraduate pharmacy students were higher than those in their male counterparts, and most of the students had at least good well-being

Medication knowledge and beliefs in patients with major depressive disorder at a tertiary health facility in north east Nigeria

Background: Achieving positive clinical outcomes with antidepressant drug therapy depends on patients having adequate knowledge and positive beliefs about their prescribed medication.Objectives: To assess medication related knowledge and beliefs about medicines in patients with major depressive disorder.Materials and Methods: A cross sectional study was carried out from December 2018 to March 2019 at Federal Neuro-Psychiatric Hospital, Maiduguri, Nigeria. Patients who agreed to participate in the study (n=151) were interviewed with patient knowledge about medication and belief about medicine questionnaires.Results: About 82.8 % of the patients had suboptimal knowledge of their medications. Over half (60.3%) of them had strong beliefs regarding the necessity of their prescribed medications. Almost half (47.7%) of them also had strong concerns about the potential harm and adverse effects of their medications. The odds for strong beliefs regarding the necessity of their prescribed medication were about 8 times greater in patients with primary level of education than those with no formal education (p=0.026, OR=8.00) and 4 times in married people (p=0.024, OR=4.77).Conclusion: Patients with major depressive disorder in this study had suboptimal knowledge of their medication and an appreciable number of them had strong beliefs regarding the need for their medications. However, about half of the patients also had strong beliefs about the potentials of their medications to cause harm. The odds to have strong beliefs on the need for medication were positively associated with disease severity, being married and increasing level of education. Interventions aimed at improving medication knowledge and addressing negative beliefs about medications are therefore recommended.Keywords: Medication knowledge, Medication beliefs, Major depressive disorder, Nigeri

Community pharmacists' perceptions and knowledge of complementary and alternative medicine (cam) in Kaduna, Nigeria

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Synthesis, Optical and Electrochemical Properties of High-Quality Cross-Conjugated Aromatic Polyketones

This paper describes the synthesis and characterization of three new aromatic polyketones with repeating units based on 2,2′-(2,5-dihexyl-1,4-phenylene) dithiophene (PTK), 2,2′-(9,9-dihexyl-9H-fluorene-2,7-diyl)dithiophene (PFTK), and 4,7-bis(3-hexylthiophen-2-yl)benzo[c][1,2,5]thiadiazole (PBTK). These polymers were obtained with a one-pot Suzuki-Miyaura cross-coupling-promoted homopolymerization to afford high-quality, defect-free polymers. Experimental and theoretical studies were applied to investigate their optical and electrical properties. The cross-conjugated nature of aromatic polyketones imparts excellent thermal stability. Exposure to acid converts the cross-conjugation to linear-conjugation, enabling the dynamic tuning of optoelectronic properties