Fundamental studies on the front contact formation resulting in a 21% efficiency silicon solar cell with printed rear and front contacts

Abstract

The contact formation on high efficiency solar cells using a high temperature process is the subject of this research. The chemical reactions between ink components and solar cell during the contact firing process are studied in detail by thermal gravimetric - differential thermo analysis. The mechanism behind the etching process and the opening of the dielectric layer are explained and the impact of the glass frit is investigated. Based on these studies, a seed layer ink was developed, optimized and tested on silicon solar cells. The developed ink was applied on high efficiency solar cells with printed front and rear contacts. At the rear side, we used a firing stable passivation layer consisting of Al2O3 and SiNx, which additionally resists the reactive compounds of the screen printed Al-paste. After applying laser fired contacts at the rear and light induced silver plating at the front, cell efficiencies of eta = 21% and fill factors of 81% could be measured

The electrical and microstructural properties of electroplated screen-printed Ag metal contacts in crystalline silicon solar cells

“…[3][4][5] Upon cooling down, the excess silicon in the glass frit epitaxially crystallizes and some of the dissolved Ag metal in the glass frit precipitates as the Ag crystallites. The reaction of the glass frit and the silicon follows a redox reaction and the reaction mechanism between Si 3 N 4 ARC and the glass frit follows accordingly, 24 2PbO + Si A SiO 2 + 2Pb (4) 12PbO (glass) + 2Si 3 N 4 A 12Pb + 6SiO 2(glass) + 4N 2(gas) (5) It shows that during the redox reaction, silicon is oxidized to silicon dioxide (SiO 2 ) and is incorporated into an already existing glass layer. At the same time, lead oxide (PbO) is reduced to elemental lead (Pb).…”

Influence of Different Metals Back Surface Field on BSF Silicon Solar Cell Performance Deposited by Thermal Evaporation Method

“…But in this method, a large amount of expensive paste is wasted with moderate passivation reducing surface reduction velocity [15][16]. Hence, several types of materials, methodology and geometrical structure have been introduced to form the back surface in order to improve the cell efficiency by researchers over the years [20][21][22][23]. In recent years, another potential cheaper contact-forming technique, deposition by evaporation, has been attempted that can replace fired silver/aluminum paste screen printed deposition forming the required thickness of back surface contact within very short time having advantages of good ohmic contact [6][17] [24][25].…”

20.1% Efficient Silicon Solar Cell With Aluminum Back Surface Field

“…So does Hilali et al [2] on comparable material by reaching 19%. In 2010, Hörteis et al [3] present 19.3% efficiency by utilizing a more advanced metal jet printing technique followed by light-induced plating (LIP). However, in this letter, we present a solar cell with conversion efficiency exceeding 20% that features a full-area Al BSF on a 1-Ω • cm FZ-Si substrate and a cell size of 2 × 2 cm 2 .…”