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Surface, Emitter and Bulk Recombination in Silicon and Development of Silicon Nitride Passivated Solar CellsKerr, Mark John, Mark.Kerr@originenergy.com.au January 2002 (has links)
[Some symbols cannot be rendered in the following metadata please see the PDF file for an accurate version of the Abstract]
¶
Recombination within the bulk and at the surfaces of crystalline silicon has been
investigated in this thesis. Special attention has been paid to the surface passivation achievable
with plasma enhanced chemical vapour deposited (PECVD) silicon nitride (SiN) films due to
their potential for widespread use in silicon solar cells. The passivation obtained with thermally
grown silicon oxide (SiO2) layers has also been extensively investigated for comparison.
¶
Injection-level dependent lifetime measurements have been used throughout this thesis to
quantify the different recombination rates in silicon. New techniques for interpreting the
effective lifetime in terms of device characteristics have been introduced, based on the physical
concept of a net photogeneration rate. The converse relationships for determining the effective
lifetime from measurements of the open-circuit voltage (Voc) under arbitrary illumination have
also been introduced, thus establishing the equivalency of the photoconductance and voltage
techniques, both quasi-static and transient, by allowing similar possibilities for all of them.
¶
The rate of intrinsic recombination in silicon is of fundamental importance. It has been
investigated as a function of injection level for both n-type and p-type silicon, for dopant
densities up to ~5x1016cm-3. Record high effective lifetimes, up to 32ms for high resistivity
silicon, have been measured. Importantly, the wafers where commercially sourced and had
undergone significant high temperature processing. A new, general parameterisation has been
proposed for the rate of band-to-band Auger recombination in crystalline silicon, which
accurately fits the experimental lifetime data for arbitrary injection level and arbitrary dopant
density. The limiting efficiency of crystalline silicon solar cells has been re-evaluated using this
new parameterisation, with the effects of photon recycling included.
¶
Surface recombination processes in silicon solar cells are becoming progressively more
important as industry drives towards thinner substrates and higher cell efficiencies. The surface
recombination properties of well-passivating SiN films on p-type and n-type silicon have been
comprehensively studied, with Seff values as low as 1cm/s being unambiguously determined.
The well-passivating SiN films optimised in this thesis are unique in that they are stoichiometric
in composition, rather than being silicon rich, a property which is attributed to the use of dilute
silane as a process gas. A simple physical model, based on recombination at the Si/SiN interface
being determined by a high fixed charge density within the SiN film (even under illumination),
has been proposed to explain the injection-level dependent Seff for a variety of differently doped
wafers. The passivation obtained with the optimised SiN films has been compared to that
obtained with high temperature thermal oxides (FGA and alnealed) and the limits imposed by
surface recombination on the efficiency of SiN passivated solar cells investigated. It is shown
that the optimised SiN films show little absorption of UV photons from the solar spectrum and
can be easily patterned by photolithography and wet chemical etching.
¶
The recombination properties of n+ and p+ emitters passivated with optimised SiN films
and thermal SiO2 have been extensively studied over a large range of emitter sheet resistances.
Both planar and random pyramid textured surfaces were studied for n+ emitters, where the
optimised SiN films were again found to be stoichiometric in composition. The optimised SiN
films provided good passivation of the heavily doped n+-Si/SiN interface, with the surface
recombination velocity increasing from 1400cm/s to 25000cm/s as the surface concentration of
electrically active phosphorus atoms increased from 7.5x1018cm-3 to 1.8x1020cm-3. The
optimised SiN films also provided reasonable passivation of industrial n+ emitters formed in a
belt-line furnace. It was found that the surface recombination properties of SiN passivated p+
emitters was poor and was worst for sheet resistances of ~150./ . The hypothesis that
recombination at the Si/SiN interface is determined by a high fixed charge density within the
SiN films was extended to explain this dependence on sheet resistance. The efficiency potential
of SiN passivated n+p cells has been investigated, with a sheet resistance of 80-100./ and a
base resistivity of 1-2.cm found to be optimal. Open-circuit voltages of 670-680mV and
efficiencies up to ~20% and ~23% appear possible for SiN passivated planar and textured cells
respectively. The recombination properties measured for emitters passivated with SiO2, both n+
and p+, were consistent with other studies and found to be superior to those obtained with SiN
passivation.
¶
Stoichiometric SiN films were used to passivate the front and rear surfaces of various
solar cell structures. Simplified PERC cells fabricated on 0.3.cm p-type silicon, with either a
planar or random pyramid textured front surface, produced high Vocs of 665-670mV and
conversion efficiencies up to 19.7%, which are amongst the highest obtained for SiN passivated
solar cells. Bifacial solar cells fabricated on planar, high resistivity n-type substrates (20.cm)
demonstrated Vocs up to 675mV, the highest ever reported for an all-SiN passivated cell, and
excellent bifaciality factors. Planar PERC cells fabricated on gettered 0.2.cm multicrystalline
silicon have also demonstrated very high Vocs of 655-659mV and conversion efficiencies up to
17.3% using a single layer anti-reflection coating. Short-wavelength internal quantum efficiency
measurements confirmed the excellent passivation achieved with the optimised stoichiometric
SiN films on n+ emitters, while long-wavelength measurements show that there is a loss of
short-circuit current at the rear surface of SiN passivated p-type cells. The latter loss is
attributed to parasitic shunting, which arises from an inversion layer at the rear surface due to
the high fixed charge (positive) density in the SiN layers. It has been demonstrated that that a
simple way to reduce the impact of the parasitic shunt is to etch away some of the silicon from
the rear contact dots. An alternative is to have locally diffused p+ regions under the rear
contacts, and a novel method to form a rear structure consisting of a local Al-BSF with SiN
passivation elsewhere, without using photolithography, has been demonstrated.
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Maranao vocabulary of moral failure and rectificationJohnston, Patricia Gwen. January 2003 (has links)
Thesis (M.A.)--Columbia International University, 2003. / Abstract. Includes bibliographical references (leaves 131-138).
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Working with unattached youngsters in a resettlement estate from an agency base.Chan, Fu-sai. January 1976 (has links)
Thesis (M. Phil.)--University of Hong Kong, 1976.
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“Det ska vara roligt att träna, det ska vara roligt att leva” : - en studie om coachers upplevelser av Compensatory health beliefsOlsson, Louise, Svensson, Maja January 2015 (has links)
Att leva strikt hälsosamt och att unna sig frestelser är två faktorer som det ofta talas om i dagens samhälle och fysisk aktivitet på fritiden har blivit viktigare då våra arbeten blir alltmer stillasittande. Frågan är dock vilken inverkan fysisk aktivitet har på hälsan när träningen genomförs som ett kompenserande beteende. Syfte: Huvudsyftet med studien är att baserat på en tolkning av coachers upplevelser av Compensatory health beliefs (CHB) skapa en vidare förståelse för fenomenet och vilken påverkan coacher kan ha på fysiskt aktiva individers CHB. Delsyftet är att lyfta fram lämpliga pedagogiska insatser som coacher utifrån sin förståelse för CHB föreslår kan bidra till en hälsosam syn på kost och träning. Metod: Föreliggande studie har en kvalitativ metodansats där intervjuer användes som datainsamling. Insamlingsmaterialet bestod av sju transkriberade intervjuer med coacher inom fysisk aktivitet. Det empiriska materialet sammanställdes till olika teman och analyserades genom en meningsanalys. Resultat: CHB var synligt hos de fysiskt aktiva främst genom uttalad synd. En påverkan skedde från coacher till klient där outtalade krav uppfattades som negativa medan genomtänkt feedback från coacherna i huvudsak upplevdes som positivt. Lärande synliggjordes även från klient till coach genom en ökad förståelse för vikten av individanpassad coaching. För att arbeta aktivt med CHB upplevdes utbildning och kunskap hos såväl coacher som klienter som särskilt viktiga faktorer. Slutsats: En uppfattning har skapats att CHB kan ha negativ inverkan på hälsan, och det behövs mer forskning för att förstå vilken påverkan CHB har på beteendeförändringar. Coacher med hög kunskapsnivå upplevs ha positiv påverkan på klienten. / To live strictly healthy and to indulge in temptations are two factors that are often spoken about in today's society and physical activity in leisure time has become more important since our work is becoming increasingly sedentary. The question is, however, what impact physical activity have on health when it is implemented as a compensatory behavior.Aim: The main aim of the study is to, based on an interpretation of coaches experiences of Compensatory health beliefs (CHB), create a further understanding of the phenomenon and what influence coaches may have on the CHB of physical active individuals. The subsidiary aim is to highlight the appropriate educational interventions that coaches, based on their understanding of CHB, proposes can contribute to a healthy approach to diet and exercise. Method: The present study has a qualitative method where interviews were used as data collection. The gathered material consisted of seven transcribed interviews with coaches in physical activity. The empirical material was interpreted and compiled into themes through a meaning categorization. Results: CHB was visible in the physically active primarily by expressed sin. An impact occurred from the coaches to the client where non expressed demands were perceived as negative, while thoughtful feedback from the coaches were generally perceived as positive. Learning was also made visible from the client to the coach through an increased understanding of the importance of individualized coaching. To work actively with CHB, training and knowledge amongst both coaches and clients were percieved as key factors. Conclusion: A perception has been created that CHB may have negative impact on health, and more research is needed to understand the impact that CHB has on behavioral changes. Coaches with a high level of knowledge is perceived to have a positive impact on the client.
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Religious beliefs and developmental factors in the psychological well-being of differing Christian faith groups : towards a model of psycho-spiritual abuseGarcia, Daniel, 1977- 23 September 2011 (has links)
The past two decades have seen a surge of research publications in the psychology of religion, with most studies affirming the salutary effects afforded by religious functioning. However, current mental health researchers have advocated for more nuanced examinations of religious constructs and more careful analysis of potentially harmful aspects of religiosity. Particularly absent from the psychological literature are the mental health effects religious beliefs may exert on parishioners. Researchers note that this is surprising given the general psychological tenet that beliefs are inextricably bound-up with affective states and general mental health. Responding to the admonition of researchers in the field, this study proposes and tests an initial model of psycho-spiritual abuse.
The proposed model of psycho-spiritual abuse hypothesizes that religious beliefs such as the theological doctrine of original sin, fundamentalist ideology, lack of self-forgiveness, and negative God-representations, in addition to familial upbringing, may negatively impact an individual’s view of self, thus fostering psychological distress. In particular, this study considers scrupulosity disorder, depression, and shame to be the primary psychiatric maladies engendered by psycho-spiritual abuse.
Two hundred thirty five parishioners from 18 Christian faith groups across the United States participated in an online survey consisting of standardized measures of original sin, fundamentalism, self-forgiveness, god image, perceived parental rearing, scrupulosity, depression, and shame. A canonical correlation analysis was conducted because it allows for the simultaneously testing of the relationship between the criterion variables (i.e., scrupulosity, depression, and shame) and predictor variables (i.e., original sin, religious fundamentalism, self-forgiveness, parental rearing perceived as rejecting, emotionally warm, and overprotective, as well as accepting, presence, and challenging God-representations) of interest.
Results reveal that greater degrees of belief in the theological doctrine of original sin as well as greater adherence to religious fundamentalist ideologies are directly and indirectly associated with scrupulous and depressive symptomatology as well as with shame-prone feelings and actions in unhealthy ways. Results also indicate that God-representations also play an essential role in scrupulosity, depression, and shame in hypothesized ways. Hence, such results further implicate the centrality of religious ideologies in the expression of psychopathology. Additionally, results seem to suggest that the direct familial contribution to the expression of psychopathology among parishioners appears to be weaker (i.e., secondary) than that of religious beliefs; this statement is based on the fact that perceived parental rearing practices were secondary contributors to the synthetic variable of psycho-spiritual beliefs in both Function 1 and 2.
Finally, these results suggest that the primary mechanism through which religious beliefs as well as familial upbringing impact parishioner psychological well-being is the resulting view of the self they engender. Therefore, results suggest that the proposed model of psycho-spiritual abuse is sound. / text
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Hur leker barn med ett begränsat gemensamt verbalt språk? : En studie om hur barn med ett begränsat gemensamt språk hittar vägar runt det verbala språket för att leka. / How does children with a limited common verbal language play? : A study about how children with a limited common language find ways around de verbal language to be able to play.Núñez Valdivia, Fabiola January 2013 (has links)
Studien har gjorts på en avdelning på en förskola som till stor del består av asylsökande barn. Studien syftar till att undersöka hur barn med ett begränsat gemensamt verbalt språk leker utifrån ett barnperspektiv. För att komma närmare ett barnperspektiv har metoden varit videoetnografisk metod i kombination med fältanteckningar och informella samtal med pedagogerna på avdelningen. Studien utgår från en fenomenologisk ansats som intresserar sig för kroppens meningsskapande. Resultaten visade att barnen hade ett stort engagerande intresse för att ha roligt med varandra. Deras lekar, förhandlingar och samtal hade som mål att få vara tillsammans och ha roligt. Kroppsspråket och den totala närvaron har visat sig vara viktig för deras icke verbala kommunikation. De är således skickliga på att signalera lek till varandra och på att improvisera via signalerna och sin fysiska närvaro. Konflikter är ofta förekommande och ibland svåra att hantera och kan bli frustrerande för barnen men viljan att ha en rolig stund tillsammans hjälper dem igenom svårigheterna. Lekens egenvärde har visats ha stor betydelse för barnen men inte som pedagogiskt verktyg utan som ett sätt att umgås med varandra och ha roligt tillsammans.
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Exploring the sense of belonging of Setswana–speaking older women in Ikageng who were forcibly relocated during apartheid / Kolobe P.C.Kolobe, Patricia Stockie January 2011 (has links)
The social displacement enforced by the South African Group Areas Act between
1954 and 1955 was understandably experienced as a destructive process with physical and
emotional consequences arising from various types of losses, separation and feelings of
helplessness. Although the forced removals affected all the people in the community - also in
later years and generations, it seems as if older people are affected the more as they still
remember the losses they experienced when they were removed from their homes and their
communities, when their heritage and their culture were displaced. The sense of belonging
being experienced by older people, who were subjected to these forceful removals, is
therefore unclear. In this study the sense of belonging is defined as the effective participation,
involvement, contribution and emersion of people when relating to their social, physical,
spiritual, emotional and cultural places. In this study older (aged 60 and above) Setswana
speaking residents of Ikageng, a community just outside Potchefstroom in the North West
Province, South Africa, who were also forcibly relocated from Kloppersville to Ikageng, 10
kilometers away from Kloppersville, were asked to identify places that are important to them
in Ikageng and to describe the meanings they attach to these places. In the research, no one
identified any places of importance in Ikageng, instead throughout the research they kept on
referring to their lives in Kloppersville, their former place of residence, the place where they
were forcibly removed from – giving purpose and direction to this study and leading to the
question: What are the experiences related to the sense of belonging of Setswana speaking older women who were forcibly relocated during Apartheid in South Africa? The older
persons’ experiences of their sense of belonging in the place where they were forcibly
relocated to must be understood in relation to the past.
A qualitative research approach was used and a narrative research design followed.
Two sets of data were gathered and are reported on in this article that focuses on the
narrations of 11 older Tswana people from the Day Care Centre for the Aged in Ikageng.
Narrative data collection and analysis, as well as a variety of qualitative research methods
and media, were used to collect data. These include: focus group discussions, the Mmogo–
MethodTM, videos, audio, photographs and observational notes. The thematic analysis of
textual data, narrative–oriented inquiry as well as visual data, established trustworthiness of
this research through crystallization.
By drawing on the deeper symbolic meaning derived through the use of the MmogomethodTM,
the study has revealed that the sense of belonging is a relational phenomenon that
cannot be understood in absence of the different relational environments. In an African
culture the relationship with the current environment resonates with the effects that historical
processes, structural abuses, discrimination, racism and devaluation had on individuals whose
lives have been uprooted. This study has shown that the older women have a micro–organic
relational sense of belonging to the place of relocation and not to the whole context and other
relational environments and that they revealed more sense of belonging towards the place
where they were relocated from. / Thesis (M.A. (Research Psychology))--North-West University, Potchefstroom Campus, 2012.
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Exploring the sense of belonging of Setswana–speaking older women in Ikageng who were forcibly relocated during apartheid / Kolobe P.C.Kolobe, Patricia Stockie January 2011 (has links)
The social displacement enforced by the South African Group Areas Act between
1954 and 1955 was understandably experienced as a destructive process with physical and
emotional consequences arising from various types of losses, separation and feelings of
helplessness. Although the forced removals affected all the people in the community - also in
later years and generations, it seems as if older people are affected the more as they still
remember the losses they experienced when they were removed from their homes and their
communities, when their heritage and their culture were displaced. The sense of belonging
being experienced by older people, who were subjected to these forceful removals, is
therefore unclear. In this study the sense of belonging is defined as the effective participation,
involvement, contribution and emersion of people when relating to their social, physical,
spiritual, emotional and cultural places. In this study older (aged 60 and above) Setswana
speaking residents of Ikageng, a community just outside Potchefstroom in the North West
Province, South Africa, who were also forcibly relocated from Kloppersville to Ikageng, 10
kilometers away from Kloppersville, were asked to identify places that are important to them
in Ikageng and to describe the meanings they attach to these places. In the research, no one
identified any places of importance in Ikageng, instead throughout the research they kept on
referring to their lives in Kloppersville, their former place of residence, the place where they
were forcibly removed from – giving purpose and direction to this study and leading to the
question: What are the experiences related to the sense of belonging of Setswana speaking older women who were forcibly relocated during Apartheid in South Africa? The older
persons’ experiences of their sense of belonging in the place where they were forcibly
relocated to must be understood in relation to the past.
A qualitative research approach was used and a narrative research design followed.
Two sets of data were gathered and are reported on in this article that focuses on the
narrations of 11 older Tswana people from the Day Care Centre for the Aged in Ikageng.
Narrative data collection and analysis, as well as a variety of qualitative research methods
and media, were used to collect data. These include: focus group discussions, the Mmogo–
MethodTM, videos, audio, photographs and observational notes. The thematic analysis of
textual data, narrative–oriented inquiry as well as visual data, established trustworthiness of
this research through crystallization.
By drawing on the deeper symbolic meaning derived through the use of the MmogomethodTM,
the study has revealed that the sense of belonging is a relational phenomenon that
cannot be understood in absence of the different relational environments. In an African
culture the relationship with the current environment resonates with the effects that historical
processes, structural abuses, discrimination, racism and devaluation had on individuals whose
lives have been uprooted. This study has shown that the older women have a micro–organic
relational sense of belonging to the place of relocation and not to the whole context and other
relational environments and that they revealed more sense of belonging towards the place
where they were relocated from. / Thesis (M.A. (Research Psychology))--North-West University, Potchefstroom Campus, 2012.
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A management service strategy for public housing in Hong Kong /Cheng, Kam-chuen. January 1995 (has links)
Thesis (M. Hous. M.)--University of Hong Kong, 1995. / Includes bibliographical references.
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Maranao vocabulary of moral failure and rectificationJohnston, Patricia Gwen. January 2003 (has links) (PDF)
Thesis (M.A.)--Columbia International University, 2003. / Abstract. Includes bibliographical references (leaves 131-138).
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