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논문 기본 정보
- 자료유형
- 학위논문
- 저자정보
- 지도교수
- Donghwan Kim
- 발행연도
- 2016
- 저작권
- 고려대학교 논문은 저작권에 의해 보호받습니다.
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Photovoltaic (PV) is most important renewable energy source in terms of globally installed capacity. The average selling price for PV module decreases with a learning rate (LR) of about 21%. Continued efforts to reduce the cost per piece along the value chain. New technologies and materials, and highly productive manufacturing equipment, are required to reduce production costs. In this study presents a new emitter formation method, “solid-phase epitaxy emitter”, that involves an applied solid-phase epitaxial growth based on the rapid thermal processing of a-Si:H thin films. This methods expect simplification and cost reduction of process through solid-phase epitaxy method.
Solid-phase epitaxial growth (SPEG) of amorphous silicon (a-Si:H) thin films was observed using transmission electron microscopy (TEM), Raman spectroscopy, UV-visible spectroscopy, and spectroscopic ellipsometry (SE). The SPEG of thin films on crystal silicon substrate occurs when annealing was carried out using rapid thermal processing (RTP) at temperatures above 600 °C. The crystallinity change with SPEG of thin films was calculated using the effective medium approximation (EMA) modelling of SE measurements. Using EMA modeling, the SPEG of thin films was shown to be affected by substrate orientation and deposition gas ratio. The activation energy, Ea, of SPEG in thin films was estimated from the change in crystallinity with temperature and time of RTP annealing. The activation energy of SPEG is 2.39 eV for intrinsic a-Si:H films (H2/SiH4=10) on Si (100). The activation energy is lower for P-/B-doped a-Si:H films (2.31 and 2.12 eV, respectively). The activation energy is the highest for SPEG of intrinsic a-Si (H2/SiH4=0) on Si (111) (3.23 eV).
Solid-phase epitaxial growth apply to form emitter in silicon solar cells. The solid-phase epitaxial growth of phosphorous-doped a-Si:H thin films was described using radio-frequency plasma-enhanced chemical vapor deposition. The phase transition of these films results from heat treatment above 600 °C. Phosphorous-doped a-Si:H produced using phosphine gas (PH3, diluted H2) exhibited a diminished crystallinity compared with intrinsic a-Si:H because of the effect of dopants. Based on this formation method, solid-phase epitaxy emitter cell was fabricated with an efficiency of 16.7%. We consider that ought to interface passivation in order to improve performance.
In order to improvement performance of this structure, it inserted into am ultra-thin oxide layer between the doped layer and substrate. The open-circuit voltage (Voc) was significantly improved via interface passivation due to insertion of the tunnel oxide layer. During oxide layer growth, a transition region, such as a sub-oxide, was observed at a depth of about 0.75 nm in the growth interface between the silicon oxide layer and silicon substrate. The properties of the less than 2 nm thick tunnel oxide layer were primarily affected by the characteristics of the transition region. The passivation characteristics of tunnel oxide layer should depend on the physical properties of the oxide. The interface trap density Dit is an important parameter in passivation and is influenced by the stoichiometry of the oxide which in turn strongly affected by the fabrication and the post annealing conditions. During heat treatment of a-Si:H thin films (for the purpose of crystallization to form doped layers), thin film blistering occurs due to hydrogen effusion on flat substrate surfaces. To minimize this behavior was seek to control the surface morphology and annealing profile. Also, the passivation quality of the tunnel oxide layer also declined for the sample annealed above 900 °C. The resistivity of the tunnel oxide layer declined precipitously for the sample annealed above 900 °C. This decline was attributed not only to local disruption of the tunnel oxide layer, but also to phosphorus diffusion. On the basis of these, implied Voc over 740 mV was achieved in n-type Si wafer through the control of the oxide stoichiometry via optimizing the annealing conditions.
Solid-phase epitaxial growth (SPEG) of amorphous silicon (a-Si:H) thin films was observed using transmission electron microscopy (TEM), Raman spectroscopy, UV-visible spectroscopy, and spectroscopic ellipsometry (SE). The SPEG of thin films on crystal silicon substrate occurs when annealing was carried out using rapid thermal processing (RTP) at temperatures above 600 °C. The crystallinity change with SPEG of thin films was calculated using the effective medium approximation (EMA) modelling of SE measurements. Using EMA modeling, the SPEG of thin films was shown to be affected by substrate orientation and deposition gas ratio. The activation energy, Ea, of SPEG in thin films was estimated from the change in crystallinity with temperature and time of RTP annealing. The activation energy of SPEG is 2.39 eV for intrinsic a-Si:H films (H2/SiH4=10) on Si (100). The activation energy is lower for P-/B-doped a-Si:H films (2.31 and 2.12 eV, respectively). The activation energy is the highest for SPEG of intrinsic a-Si (H2/SiH4=0) on Si (111) (3.23 eV).
Solid-phase epitaxial growth apply to form emitter in silicon solar cells. The solid-phase epitaxial growth of phosphorous-doped a-Si:H thin films was described using radio-frequency plasma-enhanced chemical vapor deposition. The phase transition of these films results from heat treatment above 600 °C. Phosphorous-doped a-Si:H produced using phosphine gas (PH3, diluted H2) exhibited a diminished crystallinity compared with intrinsic a-Si:H because of the effect of dopants. Based on this formation method, solid-phase epitaxy emitter cell was fabricated with an efficiency of 16.7%. We consider that ought to interface passivation in order to improve performance.
In order to improvement performance of this structure, it inserted into am ultra-thin oxide layer between the doped layer and substrate. The open-circuit voltage (Voc) was significantly improved via interface passivation due to insertion of the tunnel oxide layer. During oxide layer growth, a transition region, such as a sub-oxide, was observed at a depth of about 0.75 nm in the growth interface between the silicon oxide layer and silicon substrate. The properties of the less than 2 nm thick tunnel oxide layer were primarily affected by the characteristics of the transition region. The passivation characteristics of tunnel oxide layer should depend on the physical properties of the oxide. The interface trap density Dit is an important parameter in passivation and is influenced by the stoichiometry of the oxide which in turn strongly affected by the fabrication and the post annealing conditions. During heat treatment of a-Si:H thin films (for the purpose of crystallization to form doped layers), thin film blistering occurs due to hydrogen effusion on flat substrate surfaces. To minimize this behavior was seek to control the surface morphology and annealing profile. Also, the passivation quality of the tunnel oxide layer also declined for the sample annealed above 900 °C. The resistivity of the tunnel oxide layer declined precipitously for the sample annealed above 900 °C. This decline was attributed not only to local disruption of the tunnel oxide layer, but also to phosphorus diffusion. On the basis of these, implied Voc over 740 mV was achieved in n-type Si wafer through the control of the oxide stoichiometry via optimizing the annealing conditions.
목차
ABSTRACT------------------------------------------------------------------------------ iTABLE OF CONTENTS-------------------------------------------------------------- iiiLIST OF FIGURES--------------------------------------------------------------------- vLIST OF TABLES---------------------------------------------------------------------- x1. Introduction --------------------------------------------------------------------------- 11.1 Photovoltaic (PV) in renewable energy ----------------------------------------- 11.2 Silicon solar cells ------------------------------------------------------------------- 21.3 Trends of photovoltaic ------------------------------------------------------------- 42. Theoretical solar cells and measuring -------------------------------------------- 82.1 Operating principle of solar cells ------------------------------------------------- 82.2 Current Voltage characteristics --------------------------------------------------- 92.3 Solar cell parameters --------------------------------------------------------------- 112.4 Loss mechanism of solar cells ---------------------------------------------------- 142.5 Illuminated current-voltage (I-V) characteristics ------------------------------- 172.6 Dark current-voltage (I-V) characteristics --------------------------------------- 172.7 Quantum efficiency (QE) ---------------------------------------------------------- 222.8 Quasi-steady states photo conductance system (QSSPC) --------------------- 223. Solid-phase epitaxial growth ------------------------------------------------------- 293.1 Atomistics of epitaxial growth processes ---------------------------------------- 293.2 Temperature dependence ---------------------------------------------------------- 313.3 Substrate orientation dependence radiative recombination ------------------- 313.4 Electrically-active impurity dependence ---------------------------------------- 323.5 Electrically-inactive impurity dependence -------------------------------------- 333.6 Defect nucleation during SPEG --------------------------------------------------- 343.7 Crystallization analysis with spectroscopy ellipsometry ---------------------- 454. SPEG analysis using spectroscopic ellipsometry ------------------------------- 564.1 Introduction -------------------------------------------------------------------------- 564.2 Materials and methods ------------------------------------------------------------- 574.3 Solid-phase epitaxial growth of a-Si:H thin films ------------------------------ 584.4 Crystallization with different substrate orientations --------------------------- 634.5 Crystallization of a-Si:H thin films with deposition condition --------------- 644.6 Activation energy of SPEG of a-Si:H thin films ------------------------------- 704.7 Conclusions -------------------------------------------------------------------------- 735. Solid-phase epitaxy emitter cells -------------------------------------------------- 745.1 Introduction -------------------------------------------------------------------------- 735.2 Materials and methods ------------------------------------------------------------- 765.3 Solid-phase epitaxy emitter (SEE) ----------------------------------------------- 775.4 Solid-phase epitaxy emitter (SEE) cells ----------------------------------------- 805.5 Conclusions -------------------------------------------------------------------------- 856. Ultra-thin tunnel oxide ------------------------------------------------------------- 866.1 Introduction -------------------------------------------------------------------------- 866.2 Materials and methods ------------------------------------------------------------- 876.3 Si-O bonding via post annealing -------------------------------------------------- 896.4 Hydrogen blistering on flat surface ---------------------------------------------- 956.5 Thermal stability of tunnel oxide passivated contact -------------------------- 1006.6 Conclusions -------------------------------------------------------------------------- 1057. Summary ------------------------------------------------------------------------------- 106Reference ---------------------------------------------------------------------------------- 108
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