Investigation of the Mechanism Resulting in low Resistance Ag Thick-Film Contact to Si Solar Cells in the Context of Emitter Doping Density and Contact Firing for Current-Generation Ag Paste

The performance of SnO2/SiO2/n-Si solar cells was studied by considering various transport mechanisms including minority-carrier diffusion, carrier recombination, and tunneling through insulating layer. The tunneling current through the SiO2 layer was obtained by employing the Airy-wavefunction approach. The efficiency was calculated to determine the performance of the cells under AM1 illumination for different values of insulating layer thickness, interface state density, hole life-time, doping density of silicon substrate, and cell thickness. It was shown that the efficiency increases as the insulating layer becomes thinner due to the decrease of short-circuit current. It was also shown that the efficiency increases as the doping density increases up to 6x1022/m3 and it then decreases for higher doping densities. As the interface state density decreases, the efficiency becomes higher. In addition, the increases in the hole lifetime and cell thickness enhance the efficiency of the solar cell.

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Effect of Ag Particle Size in Thick-Film Ag Paste on the Electrical and Physical Properties of Screen Printed Contacts and Silicon Solar Cells

Journal of The Electrochemical Society ◽

10.1149/1.2126579 ◽

2006 ◽

Vol 153 (1) ◽

pp. A5 ◽

Cited By ~ 101

Author(s):

Mohamed M. Hilali ◽

Kenta Nakayashiki ◽

Chandra Khadilkar ◽

Robert C. Reedy ◽

Ajeet Rohatgi ◽

...

Keyword(s):

Particle Size ◽

Solar Cells ◽

Physical Properties ◽

Thick Film ◽

Silicon Solar Cells ◽

Ag Paste ◽

Ag Particle ◽

Screen Printed

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Investigation of the Screen-printable Ag/Cu Contact for Si Solar Cells Using Microstructural, Optical and Electrical Analyses

MRS Advances ◽

10.1557/adv.2019.438 ◽

2019 ◽

Vol 5 (8-9) ◽

pp. 431-439

Author(s):

Keming Ren ◽

Abasifreke Ebong

Keyword(s):

Solar Cells ◽

Effective Diffusion ◽

Weight Percent ◽

Glass Layer ◽

Si Solar Cells ◽

Contact Metallization ◽

Ag Crystallites ◽

Ag Paste ◽

Ag Contact ◽

The Cost

ABSTRACTIn a bid to further reduce the cost of the front Ag contact metallization in Si solar cells, Cu is the potential alternative to replace the Ag in the Ag paste. However, this requires an understanding of the contact mechanism of screen-printable Ag/Cu paste in Si solar cell through rapid thermal process. The pastes with different weight percent of Cu (0 wt%, 25 wt% and 50 wt%) were used and the Voc of the cells was reduced with the increasing weight percent of Cu. This is because the presence of Cu in the paste changed the microstructure of the Ag/Cu/Si contact through Cu doping of the glass frits and hence increasing the Tg of the glass. The increased Tg of the glass impeded the uniform spreading of the molten glass and resulted in poor wetting and etching of the SiNx, which impacted the contact as evident in ideality factor of less than unity. This also led to the formation of agglomerated Ag crystallites with features of 700 nm in length and 200 nm in depth, which is close to the p-n junction, of which depth is ∼300 nm. However, the interface glass layer acted as an effective diffusion barrier layer to prevent Cu atoms from diffusing into the Si emitter, which is quite remarkable for Cu not to diffuse into silicon at high temperature. Further investigation of the Ag/Cu contacts with the conductive AFM in conjunction with the SEM and STEM analyses revealed that the growth of Ag crystallites in the Si emitter is responsible for carrier conduction the gridlines as with the pure Ag paste.

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