Minhan Jeon

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.

Al2O3/SiON stack layers for effective surface passivation and anti-reflection of high efficiency n-type c-Si solar cells

Excellent surface passivation and anti-reflection properties of double-stack layers is a prerequisite for high efficiency of n-type c-Si solar cells. The high positive fixed charge (Q f) density of N-rich hydrogenated amorphous silicon nitride (a-SiNx:H) films plays a poor role in boron emitter passivation. The more the refractive index ( n ) of a-SiNx:H is decreased, the more the positive Q f of a-SiNx:H is increased. Hydrogenated amorphous silicon oxynitride (SiON) films possess the properties of amorphous silicon oxide (a-SiOx) and a-SiNx:H with variable n and less positive Q f compared with a-SiNx:H. In this study, we investigated the passivation and anti-reflection properties of Al2O3/SiON stacks. Initially, a SiON layer was deposited by plasma enhanced chemical vapor deposition with variable n and its chemical composition was analyzed by Fourier transform infrared spectroscopy. Then, the SiON layer was deposited as a capping layer on a 10 nm thick Al2O3 layer, and the electrical and optical properties were analyzed. The SiON capping layer with n = 1.47 and a thickness of 70 nm resulted in an interface trap density of 4.74 = 1010 cm−2 eV−1 and Q f of −2.59 = 1012 cm−2 with a substantial improvement in lifetime of 1.52 ms after industrial firing. The incorporation of an Al2O3/SiON stack on the front side of the n-type solar cells results in an energy conversion efficiency of 18.34% compared to the one with Al2O3/a-SiNx:H showing 17.55% efficiency. The short circuit current density and open circuit voltage increase by up to 0.83 mA cm−2 and 12 mV, respectively, compared to the Al2O3/a-SiNx:H stack on the front side of the n-type solar cells due to the good anti-reflection and front side surface passivation.

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%.

A Review on Silicon Oxide Sureface Passivation for High Efficiency Crystalline Silicon Solar Cell

Minimizing the carrier recombination and electrical loss through surface passivation is required for high efficiency c-Si solar cell. Usually, SiNX, SiOX, SiONX and AlOX layers are used as passivation layer in solar cell application. Silicon oxide layer is one of the good passivation layer in Si based solar cell application. It has good selective carrier, low interface state density, good thermal stability and tunneling effect. Recently tunneling based passivation layer is used for high efficiency Si solar cell such as HIT, TOPCon and TRIEX structure. In this paper, we focused on silicon oxide grown by various the method (thermal, wet-chemical, plasma) and passivation effect in c-Si solar cell.