Moon Hee Kang

The Study of Silane-Free SiC x N y Film for Crystalline Silicon Solar Cells

We deposited plasma-enhanced chemical vapor deposition silicon carbon nitride (SiC x N y ) antireflection coating and passivation layers using a silane-free process. We used a solid polymer source developed at SiXtron Advanced Materials to eliminate the storage and handling of dangerous pyrophoric silane gas. We used ammonia flow rate as a control for the chemical and optical properties in the silane-free process. As NH 3 flow rate increases, the carbon content, refractive index, extinction coefficient, and surface charge density of the film decrease. At an ammonia flow rate of 3000 sccm, which is similar to the conventional SiN x , the extinction coefficients for the two films were similar. This led to an emitter dark saturation current density (J oe ) of 404 fA/cm 2 for the two films on 45 Ω/□ emitters. However, a stack passivation of SiO 2 /SiC x N y on an 80 Ω/□ emitter resulted in an emitter dark saturation current density of 95 fA/cm 2 , which is enough to provide a good surface passivation for high efficiency solar cells. An energy conversion efficiency of 17.4% was obtained for a 149 cm 2 textured Czochralski screen-printed solar cell with this stack passivation. For a 156 cm 2 nontextured multicrystalline silicon, with only SiC x N y and a 45 Ω/□ emitter, we obtained 14.9% efficiency.

3D-modeling of a back point contact solar cell structure with a selective emitter

Three dimensional numerical simulations were performed to investigate a novel high efficiency back contact solar cell design with a selective emitter. The effect of several physical parameters (bulk lifetime, substrate doping, emitter fraction and surface recombination velocity in the gap between the emitter and BSF) on solar cell performance is explored using the SENTAURUS DEVICE™ program (formerly DESSIS™). It is found that efficiencies in excess of 22 and 20.8 percent can be achieved on p and n type substrates respectively with a bulk lifetime of 300 microseconds.

High-Efficiency n-Type Si Solar Cells With Novel Inkjet-Printed Boron Emitters

Formation of a well-passivated boron emitter for mass production of low-cost and high-efficiency n-type silicon solar cells is a major challenge in the photovoltaic industry. In this letter, we report on a novel and commercially viable method, inkjet printing, to create boron emitters. Phosphorus diffusion was used on the rear to form a back-surface held in conjunction with chemically grown oxide/silicon nitride (SiNx) stack on the front and back for surface passivation. Finally, front and back screen-printed contacts were formed through the dielectric stacks to fabricate large-area (239 cm2) n-type cells. This technology resulted in 19.0%-efficient p+-n-n+ cells with a Voc of 644 mV, a Jsc of 38.6 mA/cm2, and a fill factor of 76.3%. This demonstrates for the hrst time the promise of boron-inkjet-printing technology for low-cost and high-performance n-type Si cells.

Silane-free PECVD silicon carbon nitride (SiC x N y ) passivation and anti-reflection coatings for high efficiency silicon solar cells

Industrialized silicon solar cells were fabricated using silane-free silicon carbon nitride (SiC<inf>x</inf>N<inf>y</inf>) film as an antireflection (AR) and surface passivation layer. Sixtron Advanced Materials has developed a gas generation system to deposit the dielectric film that uses a polymeric solid source. Sixtron eliminates the cost and hazards associated with storing and handling pyrophoric silane gas. The electrical and optical properties of the new AR coating layer are investigated and compared to the SiN<inf>x</inf> films coated with silane (SiH<inf>4</inf>) gas. We tuned the film properties using NH<inf>3</inf> flow rate from previous work^1,2. In this work, we further optimized the film properties. As plasma power increases, interface trap density (D<inf>it</inf>) and flat band charge (Q<inf>fb</inf>) are reduced while refractive index and extinction coefficient remain similar³. Screen-printed 149cm² Czochralski (CZ) Si solar cells with SiC<inf>x</inf>N<inf>y</inf> AR coating layer provides an energy conversion efficiency of 17.2%, which is comparable to that of conventional SiN<inf>x</inf> coated solar cells.

Understanding and Development of Screen-Printed Front Metallization for High-Efficiency Low-to-Medium Concentrator Silicon Solar Cells

This paper reports on a methodology to achieve low-cost high-efficiency screen-printed low-to-medium concentrator Si cells and validates it by fabricating some of the highest efficiency metal paste printed cells with a simple cell design. The model shows that the highest achievable efficiency at any given concentration is a function of metal paste, contact parameters, number of fingers, and finger length due to the tradeoff between resistive and shadow losses. Consistent with the model calculations, first, 52 mm × 27 mm ~19% cells were fabricated at ~5X (suns) with a Dupont 16 A paste and ~110 μm wide 32 lines. Then, with improved 50 μm wide direct extrusion printed fingers, >20% efficient cells were achieved in the concentration range of 3-16X, along with a roadmap to ~21% efficient cells. This approach provides excellent guidelines to design grid pattern and selecting cell dimensions to achieve maximum efficiency at the desired concentration from a given printing technology and cell structure.

Development and use of a simple numerical model to quantify the impact of key photovoltaics system parameters on the levelized cost of electricity

A simple numerical model was developed in this paper to quantitatively analyze the impact of module efficiency, module cost, balance of system (BOS) cost, and financial inputs on the levelized cost of Electricity (LCOE). It is found that LCOE is a linear or nearly linear function of installed system cost (BOS+Module), loan rate, and total system derate losses. LCOE was found to be a non-linear function of system lifetime and module efficiency. User friendly charts were generated along with empirical equations to establish quantitative relationship between LCOE and system and financial parameters. A roadmap to grid parity at 9cents/kWh was developed to illustrate how to use the methodology, charts, and equations developed in this paper to achieve a target LCOE by selecting the right combination of above parameters.

Analysis of a commercial-scale photovoltaics system performance and economic feasibility

The performance of a commercial-scale (86.4 kWp) rooftop grid-connected photovoltaic (PV) system was investigated from the measured daily power generation and weather. The PV system was installed in Atlanta, GA, USA, where global solar irradiation varies from 3.3 to 9.0 kWh/m2 day (average: 4.7 kWh/m2 day). Annual power generation measured from this PV system was 110 MWh with a capacity factor of 14.5%. This is also equivalent to a carbon reduction of 25.2 tons/yr. Furthermore, for an accurate assessment of the total system derate losses and the levelized cost of electricity (LCOE), System Advisory Model modelings were performed. From the modelling, the total PV system derate losses were calculated to be 27% (including inverter loss) and the LCOE value was 14¢/kWh. Note that the installed system cost was 4.18

High performance solar cells with silicon carbon nitride (SiCxNy) antireflection coatings deposited from polymeric solid source

/W when it was installed in 2011, assuming 30 years of lifetime and a weighted average cost of capital of 5.6%. However, in 2016, one can install PV systems only at 2.2

Reduction of light induced degradation (LID) in B-doped Cz-Si solar cells by SiH 4 -free SiC x N y film

/W instead of 4.18

Optimization of SiN AR coating for Si solar cells and modules through quantitative assessment of optical and efficiency loss mechanism

/W, so the ...