Pros and cons of iron precipitates in crystalline silicon solar cells

Hannu Laine

Pros and cons of iron precipitates in crystalline silicon solar cells

Julkaisun otsikon käännös: Rautaerkaumien hyödyt ja haitat kiteisissä piiaurinkokennoissa

Hannu Laine

Tutkimustuotos: Doctoral Thesis › Collection of Articles

Abstrakti

Maailmanlaajuisesti kasvavan energiantarpeen tyydyttäminen kestävällä tavalla vaatii suuret määrät matalahiilistä energiantuotantoa. Tämä väitöskirja alkaa pohtimalla useita energia-intensiivisiä teollisuudenaloja, joiden oletetaan kasvavan paljon tulevaisuudessa, ja jotka sopivat lähtökohtaisesti hyvin yhteen erään tietyn vähähiilisen energiatuotantomuodon kanssa: aurinkosähkön. Tällaisia teollisuudenaloja ovat esimerkiksi sähköautot, meriveden suolanpoisto ja asuintilojen jäähdytys, jotka voivat kaikki periaatteessa tukea jopa TW-luokan aurinkosähkötuotantokapasiteetteja vuosisadan loppuun mennessä, helpottaen siten aurinkosähkön tuotannon vaihtelusta koituvia ongelmia. Tämä väitöskirja pyrkii auttamaan aurinkosähköteollisuutta saavuttamaan TW-luokan potentiaalinsa kehittämällä työkaluja, joilla voidaan hallita paremmin piissä olevia haitallisia epäpuhtausjäämiä, erityisesti rautaerkaumia, ja täten parantaa piipohjaisten aurinkokennojen kustannustehokkuutta. Tehokkaan rautaerkaumien karakterisointimenetelmän, synkrotronipohjaisen röntgensädefluoresenssispektroskopian tuotteliaisuutta parannetaan yli kertaluokalla kalibroimalla uusi mittausmenetelmä. Karakterisointitekniikan lisäksi myös rautaerkaumien simulaatiotekniikoiden tuotteliaisuutta parannetaan noin kertaluokalla. Tämä tehdään vertailemalla erilaisia fysikaalisia malleja rautaerkaumien simuloimiselle ja näyttämällä että yksinkertaiset ja nopeat mallit ovat tarpeeksi tarkkoja. Seuraavaksi näillä tekniikoilla parannetaan sekä vakiintuneita että tulevia aurinkokennojenvalmistusprosesseja edistämällä rautaerkaumien hallitsemista prosessien aikana. Aluksi esitellään mahdollisesti teolliseen käyttöön sopiva prosessi, jolla voidaan vähentää monikiteisen piin valmistuksessa aiheutuvia materiaalihäviöitä jopa 30 %. Esitetty prosessi lisää korkean lämpötilan toivutuksen tyypillisen piiaurinkokennoprosessin alkuun. Tämä toivutus liuottaa rautaerkaumat jättäen ne helpommin hallittavaan pistevirhemuotoon loppuprosessin ajaksi. Lopuksi esitellään kattava malli rautaerkaumien käyttäytymisestä ioni-istutetuissa aurinkokennoissa. Tässä työssä havaitaan, että ioni-istutettujen aurinkokennojen tapauksessa rautaerkaumat saattavatkin olla myös hyödyksi, eivätkä pelkästään haitaksi. Ioni-istututuksen aiheuttamat hilavirheet voivat nimittäin toimia heterogeenisinä erkaumapaikkoina raudan pistevirheille ja täten siirtää pistevirheitä piikiekon keskeltä sen pintaan, jossa ne ovat vähemmän haitallisia aurinkokennon toiminnalle. Tämä mekanismi vahvistetaan kokeellisesti, ja mekanismille esitellään fysikaalinen malli, joka mahdollistaa ioni-istutettujen aurinkokennojen prosessoinnin optimoinnin.

Julkaisun otsikon käännös	Rautaerkaumien hyödyt ja haitat kiteisissä piiaurinkokennoissa
Alkuperäiskieli	Englanti
Pätevyys	Tohtorintutkinto
Myöntävä instituutio	Aalto-yliopisto
Valvoja/neuvonantaja	Savin, Hele, Vastuuprofessori
Kustantaja	Aalto University
Painoksen ISBN	978-952-60-7909-7
Sähköinen ISBN	978-952-60-7910-3
Tila	Julkaistu - 2018
OKM-julkaisutyyppi	G5 Artikkeliväitöskirja

Tutkimusalat

pii
aurinkokenno
metalliepäpuhtaus
getterointi

Pääsy asiakirjaan

http://urn.fi/URN:ISBN:978-952-60-7910-3Lisenssi: Määrittelemätön

OtaNano
Rissanen, A. (Manager)
Aalto-yliopisto
Laitteistot/tilat: Facility
OtaNano Nanofab
Repo, P. (Manager) & Rissanen, A. (Other)
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Laitteistot/tilat: Facility

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@phdthesis{540e7c74b13c4d459a97d02df0c87b81,

title = "Pros and cons of iron precipitates in crystalline silicon solar cells",

abstract = "Meeting the increasing global energy demand in a sustainable manner requires vast amount of low carbon energy production. This Thesis begins by discussing several energy-intensive industries that are expected to grow significantly in the future, and that are intrinsically well suited to be served via a particular low carbon energy source: photovoltaics (PV). These industries include: electric vehicles, desalination and space cooling. All of these industries could sustain several TW of PV capacity during the course of the 21st century, mitigating the problems incurred by the inherent seasonal and diurnal variability of PV electricity production. This Thesis seeks to help the PV industry realize its TW-scale potential via enhancing the cost-efficiency of silicon PV through better control of unwanted iron impurities, and in particular, iron silicide precipitates. First, this Thesis increases the productivity of a state-of-the-art iron precipitate characterization technique, synchrotron-based X-ray-fluorescence, by benchmarking a new scanning method, called on-the-fly-scanning, which enables an order-of-magnitude throughput for characterized samples. In additional to experimental techniques, a similar productivity increase is realized for state-of-the-art iron precipitation simulation tools. More specifically, it is shown that up to an order-of-magnitude faster models produce adequately accurate results compared to more complex and slower models. Next, these advanced techniques are leveraged to improve both established and incipient silicon solar cell processes via enhanced control of iron silicide precipitates. First, a potentially industrially-feasible scheme to decrease the yield loss of the industry-standard silicon substrate material, multi-crystalline silicon, by up to 30 % is presented. The scheme, called dissolution-gettering, adds a high-temperature anneal in the beginning of typical silicon solar cell process. This high temperature anneal leaves iron precipitates in a more mobile state for the rest of the solar cell process, making them easier to mitigate. Lastly, a comprehensive elucidation of iron precipitation in ion-implanted emitters during silicon solar cell processing is presented. This Thesis shows that in the case of implanted emitters, iron precipitates can in certain cases be beneficial rather than deleterious. The lattice damage created by the implantation process can be used as heterogeneous precipitation sites for iron point defects and hence reduce iron point defects from the silicon wafer bulk and increase solar cell efficiency potential. This mechanism is verified experimentally and a quantitative physics-based model for the phenomenon is described. The validated model can be applied in future phosphorus- and boron-implanted silicon solar cell processing.",

keywords = "silicon, solar cell, metal impurities, gettering, pii, aurinkokenno, metalliep{\"a}puhtaus, getterointi, silicon, solar cell, metal impurities, gettering",

author = "Hannu Laine",

year = "2018",

language = "English",

isbn = "978-952-60-7909-7",

series = "Aalto University publication series DOCTORAL DISSERTATIONS",

publisher = "Aalto University",

number = "53",

address = "Finland",

school = "Aalto University",

}

TY - BOOK

T1 - Pros and cons of iron precipitates in crystalline silicon solar cells

AU - Laine, Hannu

PY - 2018

Y1 - 2018

N2 - Meeting the increasing global energy demand in a sustainable manner requires vast amount of low carbon energy production. This Thesis begins by discussing several energy-intensive industries that are expected to grow significantly in the future, and that are intrinsically well suited to be served via a particular low carbon energy source: photovoltaics (PV). These industries include: electric vehicles, desalination and space cooling. All of these industries could sustain several TW of PV capacity during the course of the 21st century, mitigating the problems incurred by the inherent seasonal and diurnal variability of PV electricity production. This Thesis seeks to help the PV industry realize its TW-scale potential via enhancing the cost-efficiency of silicon PV through better control of unwanted iron impurities, and in particular, iron silicide precipitates. First, this Thesis increases the productivity of a state-of-the-art iron precipitate characterization technique, synchrotron-based X-ray-fluorescence, by benchmarking a new scanning method, called on-the-fly-scanning, which enables an order-of-magnitude throughput for characterized samples. In additional to experimental techniques, a similar productivity increase is realized for state-of-the-art iron precipitation simulation tools. More specifically, it is shown that up to an order-of-magnitude faster models produce adequately accurate results compared to more complex and slower models. Next, these advanced techniques are leveraged to improve both established and incipient silicon solar cell processes via enhanced control of iron silicide precipitates. First, a potentially industrially-feasible scheme to decrease the yield loss of the industry-standard silicon substrate material, multi-crystalline silicon, by up to 30 % is presented. The scheme, called dissolution-gettering, adds a high-temperature anneal in the beginning of typical silicon solar cell process. This high temperature anneal leaves iron precipitates in a more mobile state for the rest of the solar cell process, making them easier to mitigate. Lastly, a comprehensive elucidation of iron precipitation in ion-implanted emitters during silicon solar cell processing is presented. This Thesis shows that in the case of implanted emitters, iron precipitates can in certain cases be beneficial rather than deleterious. The lattice damage created by the implantation process can be used as heterogeneous precipitation sites for iron point defects and hence reduce iron point defects from the silicon wafer bulk and increase solar cell efficiency potential. This mechanism is verified experimentally and a quantitative physics-based model for the phenomenon is described. The validated model can be applied in future phosphorus- and boron-implanted silicon solar cell processing.

AB - Meeting the increasing global energy demand in a sustainable manner requires vast amount of low carbon energy production. This Thesis begins by discussing several energy-intensive industries that are expected to grow significantly in the future, and that are intrinsically well suited to be served via a particular low carbon energy source: photovoltaics (PV). These industries include: electric vehicles, desalination and space cooling. All of these industries could sustain several TW of PV capacity during the course of the 21st century, mitigating the problems incurred by the inherent seasonal and diurnal variability of PV electricity production. This Thesis seeks to help the PV industry realize its TW-scale potential via enhancing the cost-efficiency of silicon PV through better control of unwanted iron impurities, and in particular, iron silicide precipitates. First, this Thesis increases the productivity of a state-of-the-art iron precipitate characterization technique, synchrotron-based X-ray-fluorescence, by benchmarking a new scanning method, called on-the-fly-scanning, which enables an order-of-magnitude throughput for characterized samples. In additional to experimental techniques, a similar productivity increase is realized for state-of-the-art iron precipitation simulation tools. More specifically, it is shown that up to an order-of-magnitude faster models produce adequately accurate results compared to more complex and slower models. Next, these advanced techniques are leveraged to improve both established and incipient silicon solar cell processes via enhanced control of iron silicide precipitates. First, a potentially industrially-feasible scheme to decrease the yield loss of the industry-standard silicon substrate material, multi-crystalline silicon, by up to 30 % is presented. The scheme, called dissolution-gettering, adds a high-temperature anneal in the beginning of typical silicon solar cell process. This high temperature anneal leaves iron precipitates in a more mobile state for the rest of the solar cell process, making them easier to mitigate. Lastly, a comprehensive elucidation of iron precipitation in ion-implanted emitters during silicon solar cell processing is presented. This Thesis shows that in the case of implanted emitters, iron precipitates can in certain cases be beneficial rather than deleterious. The lattice damage created by the implantation process can be used as heterogeneous precipitation sites for iron point defects and hence reduce iron point defects from the silicon wafer bulk and increase solar cell efficiency potential. This mechanism is verified experimentally and a quantitative physics-based model for the phenomenon is described. The validated model can be applied in future phosphorus- and boron-implanted silicon solar cell processing.

KW - silicon

KW - solar cell

KW - metal impurities

KW - gettering

KW - pii

KW - aurinkokenno

KW - metalliepäpuhtaus

KW - getterointi

KW - silicon

KW - solar cell

KW - metal impurities

KW - gettering

M3 - Doctoral Thesis

SN - 978-952-60-7909-7

T3 - Aalto University publication series DOCTORAL DISSERTATIONS

PB - Aalto University

ER -

Pros and cons of iron precipitates in crystalline silicon solar cells

Abstrakti

Tutkimusalat

Pääsy asiakirjaan

Sormenjälki

Laitteet

OtaNano

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