Gyeongbae Shim

The effect of small pyramid texturing on the enhanced passivation and efficiency of single c-Si solar cells

In this work, a simple method to form small random pyramid texturing (0.5–2 μm size) is proposed to enhance the surface passivation of commercial p-type Cz-Si wafers. Small pyramid texturing was generated with chemical nano-masking for anisotropic etching. The surface recombination velocity obtained after the passivation of the thermal oxide layer reduced from 65 and 10 cm s−1 for the large pyramids (10–15 μm size) and small pyramid (0.5–2 μm) texturing respectively. The solar cell fabricated with large pyramid texturing resulted in an efficiency of 17.82% with a current density (JSC) of 36.91 mA cm−2, an open circuit voltage (VOC) of 620 mV whereas small pyramid texturing resulted in an efficiency of 18.5% with JSC of 37.6 mA cm−2 and VOC of 628 mV. The low surface recombination velocity increases the VOC by 8 mV. The small pyramid textured wafers are found to enhance the quantum efficiency performance in both short and long wavelength regions.

Boron Diffused Layer Formation Process and Characteristics for High Efficiency N-type Crystalline Silicon Solar Cell Applications

N-type crystalline silicon solar cells have high metal impurity tolerance and higher minority carrier lifetime that increases conversion efficiency. However, junction quality between the boron diffused layer and the n-type substrate is more important for increased efficiency. In this paper, the current status and prospects for boron diffused layers in N-type crystalline silicon solar cell applications are described. Boron diffused layer formation methods (thermal diffusion and co-diffusion using a-SiOX:B), boron rich layer (BRL) and boron silicate glass (BSG) reactions, and analysis of the effects to improve junction characteristics are discussed. In-situ oxidation is performed to remove the boron rich layer. The oxidation process after diffusion shows a lower B-O peak than before the Oxidation process was changed into SiO2 phase by FTIR and BRL. The a-SiOX:B layer is deposited by PECVD using SiH4, B2H6, H2, CO2 gases in N-type wafer and annealed by thermal tube furnace for performing the P+ layer. MCLT (minority carrier lifetime) is improved by increasing SiH4 and B2H6. When a-SiOX:B is removed, the Si-O peak decreases and the B-H peak declines a little, but MCLT is improved by hydrogen passivated inactive boron atoms. In this paper, we focused on the boron emitter for N-type crystalline solar cells.

Boron diffused layer optimization by metal impurity concentration control using gettering process for n-type c-Si solar cell applications

In this paper, boron diffused layer optimization was described by metal impurity concentration control using gettering process. Boron diffusion was performed using BBr3 diffusion furnace with varying cooling rate and treated Rs with acid etching. The effect of gettering in the diffused layer was analyzed using SIMS and QSS-PC method, where by metal impurity and boron concentration and saturation current density (J0). Metal and boron retained dose was decreased from 2.04 × 10¹⁴ to 6.52 × 10¹³ atoms/cc, 1.2 × 10²⁰ to 3.54 × 10¹⁹ atoms/cc. Metal impurity and boron concentration determined SRV, MCLT, Jo. and solar cell output characteristics.

Analysis of Contact Properties by Varying the Firing Condition of AgAl Electrode for n-type Crystalline Silicon Solar Cell

n-type silicon shows the better tolerance towards metal impurities with a higher minority carrier lifetime compared to p-type silicon substrate. Due to better lifetime stability as compared to p-type during illumination made the photovoltaic community to switch toward n-type wafers for high efficiency silicon solar cells. We fabricated the front electrode of the n-type solar cell with AgAl paste. The electrodes characteristics of the AgAl paste depend on the contact junction depth that is closely related to the firing temperature. Metal contact depth with p+ emitter, with optimized depth is important as it influence the resistance. In this study, we optimize the firing condition for the effective formation of the metal depth by varying the firing condition. The firing was carried out at temperatures below 670°C with low contact depth and high contact resistance. It was noted that the contact resistance was reduced with the increase of firing temperature. The contact resistance of 5.99 mΩcm2 was shown for the optimum firing temperature of 865°C. Over 900°C, contact junction is bonded to the Si through the emitter, resulting the contact resistance to shunt. we obtained photovoltaic parameter such as fill factor of 76.68%, short-circuit current of 40.2 mA/cm, open-circuit voltage of 620 mV and convert efficiency of 19.11%.