Metastabilne rozkłady defektów w materiałach fotowoltaicznych Cu(In,Ga)Se2

Aleksander Urbaniak

Abstract

The work concerns the physics of metastable phenomena in solar cells based on Cu(In,Ga)Se2 ternary compound. The aim of this study was to verify the available theoretical predictions relating to the Cu(In,Ga)Se2, in particular to, described in the literature, metastable defects in Cu(In,Ga)Se2 and experimental verification of the mechanisms leading to the formation of metastable defect distributions in CIGS cells. Experiments were carried out using the electrical and optical methods of semiconductor characterization. The obtained experimental results of work allowed to link metastabilities in CIGS cells with the properties of the complex vacancies VSe-VCu. In particular, the energies of creation and relaxation of metastability were calculated, showing good agreement with theoretical predictions of the complex model VSe-VCu. Based on defect prosperities explanation of metastable changes on space charge distributions have been proposed and assessed to changes of Vse-Vcu divacancy defect configurations, depending on Fermi quasi-level position in the junction. Apart from that, the non-exponential kinetics of proceses, which lead to creation, and relaxation of metastabilities and time dependence of relaxation decays on bias/light pulse duration has been linked to the model of defect conversion in configurational space. The hypothesis that those features may come from energy distribution of barrier for defect conversion as also from non-uniform availability of free carriers in the junction has been proposed. Subbandgap signal observed in photocapacitance and photocurrent spectra was interpreted in light of VSe-VCu properties. In addition, the mechanism, which may leads to metastable changes in photocapacitance and photocurrent spectra’s. Using positron annihilation measurements, the preliminary results confirming existence of selenium and copper vacancies have been obtained and linked to the conductivity of the material. The work can be treated as a step forward in understanding of processes taking place in CIGS devices. The most important result of this work is explanation of many, up to now treated as independent, experimental facts with one model, based on properties of one defect
Diploma typeDoctor of Philosophy
Author Aleksander Urbaniak (FP / SD)
Aleksander Urbaniak,,
- Semiconductors Division
Title in PolishMetastabilne rozkłady defektów w materiałach fotowoltaicznych Cu(In,Ga)Se2
Languagepl polski
Certifying UnitFaculty of Physics (FP)
Disciplinephysics / (physical sciences domain) / (physical sciences)
Defense Date19-10-2010
Supervisor Małgorzata Igalson (FP / SD)
Małgorzata Igalson,,
- Semiconductors Division

Internal reviewers Rajmund Bacewicz (FP / SD)
Rajmund Bacewicz,,
- Semiconductors Division
External reviewers Maria Kamińska - [Faculty of Physics [University of Warsaw (UW)]]
Maria Kamińska,,
-
- Wydział Fizyki
Pages119
Keywords in Englishxxx
Abstract in EnglishThe work concerns the physics of metastable phenomena in solar cells based on Cu(In,Ga)Se2 ternary compound. The aim of this study was to verify the available theoretical predictions relating to the Cu(In,Ga)Se2, in particular to, described in the literature, metastable defects in Cu(In,Ga)Se2 and experimental verification of the mechanisms leading to the formation of metastable defect distributions in CIGS cells. Experiments were carried out using the electrical and optical methods of semiconductor characterization. The obtained experimental results of work allowed to link metastabilities in CIGS cells with the properties of the complex vacancies VSe-VCu. In particular, the energies of creation and relaxation of metastability were calculated, showing good agreement with theoretical predictions of the complex model VSe-VCu. Based on defect prosperities explanation of metastable changes on space charge distributions have been proposed and assessed to changes of Vse-Vcu divacancy defect configurations, depending on Fermi quasi-level position in the junction. Apart from that, the non-exponential kinetics of proceses, which lead to creation, and relaxation of metastabilities and time dependence of relaxation decays on bias/light pulse duration has been linked to the model of defect conversion in configurational space. The hypothesis that those features may come from energy distribution of barrier for defect conversion as also from non-uniform availability of free carriers in the junction has been proposed. Subbandgap signal observed in photocapacitance and photocurrent spectra was interpreted in light of VSe-VCu properties. In addition, the mechanism, which may leads to metastable changes in photocapacitance and photocurrent spectra’s. Using positron annihilation measurements, the preliminary results confirming existence of selenium and copper vacancies have been obtained and linked to the conductivity of the material. The work can be treated as a step forward in understanding of processes taking place in CIGS devices. The most important result of this work is explanation of many, up to now treated as independent, experimental facts with one model, based on properties of one defect
Thesis file
Urbaniak.pdf 4.44 MB
Citation count*5 (2020-10-22)

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