Rautaerkaumien kokojakauman mallintaminen fosfori-istutetuissa piiaurinkokennoissa

A pivotal phase in the manufacturing of crystalline silicon solar cells is the formation of the charge collecting pn-junction. Typically, the junction is created via dopant in-diffusion, but lately creating it through implantation has also raised interest. Implantation offers several potential benefits compared to diffusion, such as fewer processing steps and better process control. However, the differences between diffused and implanted junctions with respect to gettering, that is, the control of harmful metal impurities are not yet fully understood. This work studies the precipitation and diffusion of iron in intentionally iron-contaminated phosphorus-implanted silicon solar cells under varying time-temperature profiles. In this study, it is shown that unlike in the case of diffused cells, not only the total amount of precipitated iron, but also the precipitate size distribution of iron can be important when minimizing the harmful effects of iron on the performance of implanted solar cells. A slow cooling from the implant activation temperature to a moderate gettering anneal temperature can result in few, but large iron precipitates at the implanted surface, which improves the bulk minority carrier diffusion length but reduces the open circuit voltage of the solar cell. However, by first forcing bulk precipitation by quenching the wafers to room temperature before the gettering anneal, a large number of small precipitates is formed, resulting in a high open circuit voltage. The iron precipitate size distributions are analyzed in detail via a heterogeneous iron precipitation model and the simulation results are validated with synchrotronbased micro-X-ray fluo-rescence measurements. It is shown that the precipitate size distribution after the gettering anneal can be predicted, if the gettering efficiency of the gettering anneal in question is known. Thus, the next step towards predictive impurity-to-efficiency modeling of implanted cells is predicting the gettering efficiency based solely on the implantation parameters.Keskeinen vaihe piiaurinkokennojen valmistuksessa on varauksen keräävän liitoksen valmistus. Perinteisesti liitos valmistetaan diffusoimalla seosatomeita piikiekkoon, mutta viime aikoina liitoksen luominen istuttamalla on myös herättänyt mielenkiintoa. Verrattuna perinteiseen diffuusioon, istutus on paremmin hallittavissa ja sen avulla voidaan vähentää prosessivaiheiden määrää. Vahingollisten metalliepäpuhtauksien getterointi, eli niiden haittavaikutuksen minimointi kennoprosessin aikana ei ole kuitenkaan niin laajasti ymmärretty istutetuissa kuin diffusoiduissa kennoissa. Tämä työ tutkii rautaepäpuhtauksien erkautumista ja diffuusioita tarkoituksella kontaminoiduissa piiaurinkokennoissa erilaisten lämpökäsittelyiden aikana. Työn tulokset osoittavat, että toisin kuin diffusoiduissa kennoissa, istutetuissa kennoissa erkautuneen raudan kokonaismäärän lisäksi myös erkaumien kokojakaumalla on merkitystä, mikäli raudan negatiiviset vaikutukset halutaan minimoida. Hidas jäähdytys istutuksen aktivointilämpötilasta getterointilämpötilaan voi johtaa harvoihin, mutta isoihin rautaerkaumiin istutetulla pinnalla, mikä lisää vähemmistövarauksenkuljettajan diffuusiopituutta bulkissa, mutta saattaa vähentää kennon avoimen piirin jännitettä. Toisaalta mikäli kennot jäähdytetään nopeasti aktivaatiolämpötilasta huoneen lämpötilaan, syntyy useita, pieniä erkaumia, jotka eivät vahingoita avoimen piirin jännitettä, mutta saattavat rajoittaa diffuusiopituutta bulkissa. Rautaerkaumien kokojakaumia tutkitaan heterogeenisellä erkaumamallilla ja simuloidut kokojakaumat vahvistetaan vertaamalla niitä synkrotroniavusteisella mikro-röntgenfluoresenssi mittauksilla. Työssä näytetään, että kokojakauma getterointiprosessin jälkeen pystytään ennustamaan, mikäli getterointiprosessin aikana bulkista vähentynyt rautakonsentraatio tiedetään etukäteen. Seuraava tutkimusaskel on ennustavan mallin kehittäminen, joka pystyisi ennustamaan rautakonsentraation vähentymisen pelkkien istutusparametrien avulla

Meeting Global Cooling Demand with Photovoltaics during the 21st Century

Space conditioning, and cooling in particular, is a key factor in human productivity and well-being across the globe. During the 21st century, global cooling demand is expected to grow significantly due to the increase in wealth and population in sunny nations across the globe and the advance of global warming. The same locations that see high demand for cooling are also ideal for electricity generation via photovoltaics (PV). Despite the apparent synergy between cooling demand and PV generation, the potential of the cooling sector to sustain PV generation has not been assessed on a global scale. Here, we perform a global assessment of increased PV electricity adoption enabled by the residential cooling sector during the 21st century. Already today, utilizing PV production for cooling could facilitate an additional installed PV capacity of approximately 540 GW, more than the global PV capacity of today. Using established scenarios of population and income growth, as well as accounting for future global warming, we further project that the global residential cooling sector could sustain an added PV capacity between 20-200 GW each year for most of the 21st century, on par with the current global manufacturing capacity of 100 GW. Furthermore, we find that without storage, PV could directly power approximately 50% of cooling demand, and that this fraction is set to increase from 49% to 56% during the 21st century, as cooling demand grows in locations where PV and cooling have a higher synergy. With this geographic shift in demand, the potential of distributed storage also grows. We simulate that with a 1 m$^3$ water-based latent thermal storage per household, the fraction of cooling demand met with PV would increase from 55% to 70% during the century. These results show that the synergy between cooling and PV is notable and could significantly accelerate the growth of the global PV industry

Meeting Global Cooling Demand with Photovoltaics during the 21st Century

Space conditioning, and cooling in particular, is a key factor in human productivity and well-being across the globe. During the 21st century, global cooling demand is expected to grow significantly due to the increase in wealth and population in sunny nations across the globe and the advance of global warming. The same locations that see high demand for cooling are also ideal for electricity generation via photovoltaics (PV). Despite the apparent synergy between cooling demand and PV generation, the potential of the cooling sector to sustain PV generation has not been assessed on a global scale. Here, we perform a global assessment of increased PV electricity adoption enabled by the residential cooling sector during the 21st century. Already today, utilizing PV production for cooling could facilitate an additional installed PV capacity of approximately 540 GW, more than the global PV capacity of today. Using established scenarios of population and income growth, as well as accounting for future global warming, we further project that the global residential cooling sector could sustain an added PV capacity between 20-200 GW each year for most of the 21st century, on par with the current global manufacturing capacity of 100 GW. Furthermore, we find that without storage, PV could directly power approximately 50% of cooling demand, and that this fraction is set to increase from 49% to 56% during the 21st century, as cooling demand grows in locations where PV and cooling have a higher synergy. With this geographic shift in demand, the potential of distributed storage also grows. We simulate that with a 1 m$^3$ water-based latent thermal storage per household, the fraction of cooling demand met with PV would increase from 55% to 70% during the century. These results show that the synergy between cooling and PV is notable and could significantly accelerate the growth of the global PV industry

Preconception Mental Health, Socioeconomic Status, and Pregnancy Outcomes in Primiparous Women

Background:One in four women of childbearing age has some degree of mental disorders and are, therefore, prone to both pregnancy complications and adverse health outcomes in their offspring. We aimed to evaluate the impact of preconception severe mental disorders on pregnancy outcomes in primiparous women. MethodsThe study cohort was composed of 6,189 Finnish primiparous women without previously diagnosed diabetes, who delivered between 2009 and 2015, living in the city of Vantaa, Finland. Women were classified to have a preconception severe mental disorder if they had one or more outpatient visits to a psychiatrist or hospitalization with a psychiatric diagnosis 1 year before conception. Data on pregnancies, diagnoses, and pregnancy outcomes were obtained from national registers at an individual level. ResultsPrimiparous women with preconception severe psychiatric diagnosis were younger, more often living alone, smokers, and had lower educational attainment and lower taxable income than women without psychiatric diagnosis (for all p < 0.001). Of all women, 3.4% had at least one psychiatric diagnosis. The most common psychiatric diagnoses were depression and anxiety disorders. The most common comorbidity was the combination of depression and anxiety disorders. There were no differences in the need for respiratory treatments, admissions to the neonatal intensive care unit, or antibiotic treatments between the offspring's groups. ConclusionAlthough primiparous women had severe mental disorders, the well-being of newborns was good. The most common severe mental health disorders were depression and anxiety disorders, and psychiatric comorbidity was common. Women with severe mental disorders more often belonged to lower socioeconomic groups.Peer reviewe