Reducing surface recombination in black silicon photovoltaic devices using atomic layer deposition

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Reducing surface recombination in black silicon photovoltaic devices using atomic layer deposition

Julkaisun otsikon käännös: Mustaa piitä hyödyntävien valosähköisten komponenttien pintarekombinaation vähentäminen atomikerroskasvatuksen avulla

Päivikki Repo

Tutkimustuotos: Doctoral Thesis › Collection of Articles

Abstrakti

Piiaurinkokennojen pintarekombinaatio pienentää varauksenkuljettajien keräystodennäköisyyttä ja voi näin ollen laskea aurinkokennojen hyötysuhdetta. Tämän epäsuotuisan ilmiön vähentämistä tutkitaan tässä työssä passivoimalla piin pinta erilaisilla atomikerroskasvatetuilla (ALD) ohutkalvoilla. Pintapassivoinnin laatu alumiinioksidilla (Al2O3) tai hafniumoksidilla (HfO2) riippuu ALD-prosessissa käytettävästä oksidantista. Alumiininitridin (AlN) tapauksessa korkeampi kasvatuslämpötila johtaa parempaan pintapassivointiin ja yli 1 ms:n elinaika on saavutettavissa lisäämällä koronavarausta kiekkojen pinnalle. Kokonaisuudessaan kaikki tässä työssä tutkitut ohutkalvot takaavat hyvän pintapassivoinnin ja hyvälaatuisen ohutkalvo/pii -rajapinnan. Pintapassivoinnin roolista tulee vielä suurempi mustan piin (nanokuvioitu piin pinta) tapauksessa suuremman pinta-alan johtaessa korkeampaan pintarekombinaationopeuteen. Musta pii on herättänyt mielenkiintoa erityisesti potentiaalisena aurinkokennojen etupinnan kuviointina, koska se vähentää pintaheijastusta laajalla aallonpituusalueella ja myös suurilla tulokulmilla. Hyöty matalasta pintaheijastuksesta on kuitenkin jäänyt vähäiseksi suuren pintarekombinaation vuoksi. Tässä työssä osoitetaan, että konformaalinen ALD alumiinioksidi voi ratkaista mustan piin pintapassivointiongelman. Erinomaisen pintapassivoinnin lisäksi Al2O3 laskee jo valmiiksi matalaa heijastusta entisestään: alle 1 %:n heijastus saavutetaan koko aurinkokennoille merkityksellisellä aallonpituusalueella. Koska pintapassivointiongelma on saatu ratkaistua, testataan mustan piin toimivuutta myös erilaisissa valosähköisissä komponenteissa mukaan lukien kaksi aurinkokennoa ja valodiodi. Ensimmäiseksi osoitetaan, ettei emitteridiffuusio heikennä mustan piin optisia ominaisuuksia ja että myös korkeasti boorilla seostettu mustan piin pinta saadaan tehokkaasti passivoitua alumiinioksidilla. Tätä tietoa hyödynnetään n-tyypin etukontaktikennojen valmistuksessa, joiden etupinnalla on mustaa piitä ja Al2O3-kalvo. Näillä kennoilla saavutetaan 18.7 %:n hyötysuhde. Vielä korkeampi hyötysuhde – 22.1 % – saavutetaan takakontaktikennoilla. Lopuksi mustan piin ja ALD Al2O3 -passivoinnin yhdistelmää hyödynnetään valodiodissa, jolla saavutetaan yli 96 %:n kvanttihyötysuhde koko mitatulla spektrialueella (250-950 nm). Tämä osoittaa, että mustan piin ja ALD Al2O3 passivoinnin yhdistelmän soveltuvuus ei rajoitu ainoastaan aurinkokennoihin, vaan potentiaalisia käyttökohteita ovat myös muut optoelektroniikan sovellukset.

Julkaisun otsikon käännös	Mustaa piitä hyödyntävien valosähköisten komponenttien pintarekombinaation vähentäminen atomikerroskasvatuksen avulla
Alkuperäiskieli	Englanti
Pätevyys	Tohtorintutkinto
Myöntävä instituutio	Aalto-yliopisto
Valvoja/neuvonantaja	Savin, Hele, Vastuuprofessori
Kustantaja	Aalto University
Painoksen ISBN	978-952-60-6918-0
Sähköinen ISBN	978-952-60-6919-7
Tila	Julkaistu - 2016
OKM-julkaisutyyppi	G5 Artikkeliväitöskirja

Tutkimusalat

musta pii
atomikerroskasvatus
pintapassivointi
valosähköinen komponentti

YK:n kestävän kehityksen tavoitteet

Tämä tuotos edistää seuraavia kestävän kehityksen tavoitteita:

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http://urn.fi/URN:ISBN:978-952-60-6919-7Lisenssi: Määrittelemätön

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@phdthesis{ce2cff07407f498da2b905b3f83c2bb7,

title = "Reducing surface recombination in black silicon photovoltaic devices using atomic layer deposition",

abstract = "Surface recombination in silicon solar cells decreases the collection probability of charge carriers and can hence lower the cell efficiency significantly. The reduction of this detrimental effect is addressed in this work by passivating the surface with different atomic layer deposited (ALD) thin film coatings. It is shown that surface passivation with aluminum oxide (Al2O3) or hafnium oxide (HfO2) is dependent on the oxidant used in the ALD process. Higher deposition temperatures lead to better surface passivation with aluminum nitride (AlN) films where carrier lifetimes of more than 1 ms can be reached with additional corona charge. In general, all of the thin films studied here provide good surface passivation with low values for interface defect density. Surface passivation becomes even more important in the case of black silicon (b-Si), i.e. nanostructured silicon surface, where the large surface area results in high surface recombination velocity. Black silicon itself has gained much interested especially for photovoltaic applications due to its low surface reflectance on a wide spectral range and acceptance angle. However, the increase in the surface recombination has always hindered the application of b-Si e.g. in solar cells. This work presents that ALD Al2O3 can solve this issue by providing completely conformal coating and excellent passivation also on nanostructured surfaces. In addition to surface passivation, Al2O3 coating further reduces the reflectance leading to values less than 1 % on the whole spectral range relevant for solar cell operation. As good surface passivation is reached on b-Si, its applicability on different photovoltaic devices including two types of solar cells and a photodiode is demonstrated. First, it is shown that different emitter diffusion processes do not hinder the optical properties of black silicon and that excellent surface passivation is also reached on boron doped emitters using ALD Al2O3. This discovery is then applied in the fabrication of n-type front contact solar cells with b-Si and Al2O3 passivation on the front surface and an efficiency of 18.7 % is reached. Even higher efficiencies of 22.1 % are gained with back contact solar cells. This is so far the highest efficiency reached with black silicon solar cells. Finally, Al2O3 surface passivation and black silicon are applied on induced junction photodiodes and external quantum efficiency of 96 % is reached on the measured wavelength range of 250-950 nm. This proves that the use of b-Si and Al2O3 surface passivation is not limited only to solar cells but also other optoelectronic applications can benefit from it.",

keywords = "black silicon, atomic layer deposition, surface passivation, photovoltaic devices, musta pii, atomikerroskasvatus, pintapassivointi, valos{\"a}hk{\"o}inen komponentti, black silicon, atomic layer deposition, surface passivation, photovoltaic devices",

author = "P{\"a}ivikki Repo",

year = "2016",

language = "English",

isbn = "978-952-60-6918-0",

series = "Aalto University publication series DOCTORAL DISSERTATIONS",

publisher = "Aalto University",

number = "139",

address = "Finland",

school = "Aalto University",

}

TY - BOOK

T1 - Reducing surface recombination in black silicon photovoltaic devices using atomic layer deposition

AU - Repo, Päivikki

PY - 2016

Y1 - 2016

N2 - Surface recombination in silicon solar cells decreases the collection probability of charge carriers and can hence lower the cell efficiency significantly. The reduction of this detrimental effect is addressed in this work by passivating the surface with different atomic layer deposited (ALD) thin film coatings. It is shown that surface passivation with aluminum oxide (Al2O3) or hafnium oxide (HfO2) is dependent on the oxidant used in the ALD process. Higher deposition temperatures lead to better surface passivation with aluminum nitride (AlN) films where carrier lifetimes of more than 1 ms can be reached with additional corona charge. In general, all of the thin films studied here provide good surface passivation with low values for interface defect density. Surface passivation becomes even more important in the case of black silicon (b-Si), i.e. nanostructured silicon surface, where the large surface area results in high surface recombination velocity. Black silicon itself has gained much interested especially for photovoltaic applications due to its low surface reflectance on a wide spectral range and acceptance angle. However, the increase in the surface recombination has always hindered the application of b-Si e.g. in solar cells. This work presents that ALD Al2O3 can solve this issue by providing completely conformal coating and excellent passivation also on nanostructured surfaces. In addition to surface passivation, Al2O3 coating further reduces the reflectance leading to values less than 1 % on the whole spectral range relevant for solar cell operation. As good surface passivation is reached on b-Si, its applicability on different photovoltaic devices including two types of solar cells and a photodiode is demonstrated. First, it is shown that different emitter diffusion processes do not hinder the optical properties of black silicon and that excellent surface passivation is also reached on boron doped emitters using ALD Al2O3. This discovery is then applied in the fabrication of n-type front contact solar cells with b-Si and Al2O3 passivation on the front surface and an efficiency of 18.7 % is reached. Even higher efficiencies of 22.1 % are gained with back contact solar cells. This is so far the highest efficiency reached with black silicon solar cells. Finally, Al2O3 surface passivation and black silicon are applied on induced junction photodiodes and external quantum efficiency of 96 % is reached on the measured wavelength range of 250-950 nm. This proves that the use of b-Si and Al2O3 surface passivation is not limited only to solar cells but also other optoelectronic applications can benefit from it.

AB - Surface recombination in silicon solar cells decreases the collection probability of charge carriers and can hence lower the cell efficiency significantly. The reduction of this detrimental effect is addressed in this work by passivating the surface with different atomic layer deposited (ALD) thin film coatings. It is shown that surface passivation with aluminum oxide (Al2O3) or hafnium oxide (HfO2) is dependent on the oxidant used in the ALD process. Higher deposition temperatures lead to better surface passivation with aluminum nitride (AlN) films where carrier lifetimes of more than 1 ms can be reached with additional corona charge. In general, all of the thin films studied here provide good surface passivation with low values for interface defect density. Surface passivation becomes even more important in the case of black silicon (b-Si), i.e. nanostructured silicon surface, where the large surface area results in high surface recombination velocity. Black silicon itself has gained much interested especially for photovoltaic applications due to its low surface reflectance on a wide spectral range and acceptance angle. However, the increase in the surface recombination has always hindered the application of b-Si e.g. in solar cells. This work presents that ALD Al2O3 can solve this issue by providing completely conformal coating and excellent passivation also on nanostructured surfaces. In addition to surface passivation, Al2O3 coating further reduces the reflectance leading to values less than 1 % on the whole spectral range relevant for solar cell operation. As good surface passivation is reached on b-Si, its applicability on different photovoltaic devices including two types of solar cells and a photodiode is demonstrated. First, it is shown that different emitter diffusion processes do not hinder the optical properties of black silicon and that excellent surface passivation is also reached on boron doped emitters using ALD Al2O3. This discovery is then applied in the fabrication of n-type front contact solar cells with b-Si and Al2O3 passivation on the front surface and an efficiency of 18.7 % is reached. Even higher efficiencies of 22.1 % are gained with back contact solar cells. This is so far the highest efficiency reached with black silicon solar cells. Finally, Al2O3 surface passivation and black silicon are applied on induced junction photodiodes and external quantum efficiency of 96 % is reached on the measured wavelength range of 250-950 nm. This proves that the use of b-Si and Al2O3 surface passivation is not limited only to solar cells but also other optoelectronic applications can benefit from it.

KW - black silicon

KW - atomic layer deposition

KW - surface passivation

KW - photovoltaic devices

KW - musta pii

KW - atomikerroskasvatus

KW - pintapassivointi

KW - valosähköinen komponentti

KW - black silicon

KW - atomic layer deposition

KW - surface passivation

KW - photovoltaic devices

M3 - Doctoral Thesis

SN - 978-952-60-6918-0

T3 - Aalto University publication series DOCTORAL DISSERTATIONS

PB - Aalto University

ER -

Reducing surface recombination in black silicon photovoltaic devices using atomic layer deposition

Abstrakti

Tutkimusalat

YK:n kestävän kehityksen tavoitteet

Pääsy asiakirjaan

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