Modeling and optimization of PECVD processes and equipment used for manufacturing thin film photovoltaic devices

Özkol, Engin
Plasma enhanced chemical vapor deposition (PECVD) is a common technique used in thin film based device fabrication. Operation conditions of a PECVD reactor need to be optimized in terms of deposition conditions as well as plasma cleaning procedures to deliver desired deposited material qualities. In addition, interactions with external support systems such as gas lines and cabinet, compressors and utility production units need to be understood and characterized. Modeling, whether based on fundamental principles or experimental data, is an essential tool in this optimization process, reducing the time required for experimentation. In this work, a first principles based thermal model of the system is constructed, guiding the design of an improved PECVD chamber delivering better substrate temperature levels and uniformity. On the other hand, material optimization work is supported by the identification of empirical models based on designed experiments, since fundamental models for these interactions are too complicated to be modeled accurately. Individual thin film layers, involved in thin film photovoltaic devices, were optimized in terms of crystallinity, thickness, deposition rate as well as critical optical and electrical properties. The growth of hydrogenated silicon thin films in amorphous (a-Si:H), nano-crystalline, and micro-crystalline regions with intrinsic, nand p- doping types were characterized and optimized. Amorphous silicon nitride (SiNx) thin films with tunable silicon and nitrogen concentration, silver thin films with controlled thickness profile down to nm scale, aluminum doped zinc oxide (AZO) thin films with repeatable uniform conductivity were realized successfully. After completing the optimization of these individual layers, several thin film silicon based photovoltaic devices were fabricated. The different performances that are reported in this work include a p-i-n structured homojunction a-Si:H device, a heterojunction device and a heterojunction with intrinsic thin layer (HIT) structured device. The efficiency values of 2.9 % (initial) for a-Si:H p-i-n structure, 15.9 % for heterojunction solar device and 12.5 % for one sided HIT device were recorded.


Characterization and enhancement of IR optical and tribological properties of DLC films synthesized by RF-PECVD
Taburoğlu, Vahit Eren; Özenbaş, Ahmet Macit; Akata Kurç, Burcu; Department of Micro and Nanotechnology (2017)
This thesis analyzes the hydrogenated amorphous diamond like carbon (a-DLC) films coated on aluminum substrates by the technique of plasma enhanced chemical vapor deposition (PECVD). Effects of film thickness, hydrogen content and RF power on the tribology, optical characteristics and structure are observed and studied in detail. DLC films have compressive intrinsic stresses by default. Surface topography revealed by an interferometer shows that too low/high compressive stress is detrimental to the film. In...
Development of hole transport transparent conductive electrodes for n-type crystalline silicon solar cells
Akdemir, Ozan; Bek, Alpan; İmer, Muhsine Bilge; Department of Micro and Nanotechnology (2018)
Conventional transparent conductive electrodes (TCEs) used in crystal silicon (c-Si) solar cells are commonly made of indium tin oxide (ITO) which provides low sheet resistance and high transparency. However, due to indium scarcity, ITO layers increase the fabrication cost; thus, alternative TCEs, such as fluorine-doped tin oxide (FTO), zinc oxide (ZnO), metal nanowires and Oxide/Metal/Oxide (OMO) multilayers, are being investigated. Conventional solar cells also make use of doped layers, to create the junc...
Optimization of n(+) nc-Si:H and a-SiNx:H layers for their application in nc-Si:H TFT
ANUTGAN, TAMİLA; Anutgan, Mustafa; Atilgan, Ismail; Katircioglu, Bayram (Elsevier BV, 2011-02-25)
The n-type doped silicon thin films were deposited by plasma enhanced chemical vapor deposition (PECVD) technique at high and low H-2 dilutions. High H-2 dilution resulted in n(+) nanocrystalline silicon films (n(+) nc-Si:H) with the lower resistivity (rho similar to 0.7 Omega cm) compared to that of doped amorphous silicon films (similar to 900 0 cm) grown at low H-2 dilution. The change of the lateral rho of n(+) nc-Si:H films was measured by reducing the film thickness via gradual reactive ion etching. T...
Kinetic investigation of chemical vapor deposition of B4C on tungsten substrate
Karaman, Mustafa; Sezgi, Naime Aslı; Doğu, Timur; Ozbelge, H. Onder (2006-12-01)
Production of beta-rhombohedral boron carbide (B4C) on a tungsten substrate by the chemical vapor deposition from a BCl3-H-2-CH4 gas mixture was achieved. An impinging-jet reactor was used to minimize the mass-transfer limitations on the reaction kinetics, which made a detailed kinetic investigation possible. Results of the XRD and XPS analyses showed that the solid product formed on the substrate is a rhombohedral B4C phase. Both dichloroborane and boron carbide formation rates were found to increase with ...
Investigation of silver-induced crystallization of germanium thin films fabricated on different substrates
Kabacelik, Ismail; KULAKCI, MUSTAFA; Turan, Raşit (2015-06-01)
Silver-induced crystallizations of amorphous germanium (alpha-Ge) thin films were fabricated through electron beam evaporation on crystalline silicon (c-Si) (100), aluminum-doped zinc oxide (AZO), and glass substrates at room temperature. The solid-phase crystallization (SPC) of alpha-Ge films was investigated for various post-annealing temperatures between 300 and 500 degrees C for 60 min. Two crystallization approaches were compared: SPC and metal-induced crystallization (MIC). The structural properties o...
Citation Formats
E. Özkol, “Modeling and optimization of PECVD processes and equipment used for manufacturing thin film photovoltaic devices,” Ph.D. - Doctoral Program, Middle East Technical University, 2014.