Rear-surface passivation technology for crystalline silicon solar cells: A versatile process for mass production

Abstract

Over the past few years, significant progress has been made in integrating cell structure improvements on the cell front side into mass production, such as, e.g., selective emitters. With these improvements, the large-area aluminum back-surface field clearly limits the efficiency of typical industrial cells. Dielectric passivation of the cell rear side provides a means for significant improvement. However, it needs to be adapted to different wafer materials and cell structures in order to obtain economic efficiency, allowing for its implementation in mass production. In this paper, we report on our cost-effective passivated emitter and rear cell (PERC) technology that easily adapts to various wafer materials, such as multicrystalline, quasi-monocrystalline, and Czochralskigrown monocrystalline material. It is suitable for wafer thicknesses down to 120 μm and all base resistivities in the range from 1 to 3.5 Ω·cm. Additionally, we investigate the compatibility with homogeneous and selective emitters on the cell front side. For commercially available Czochralski wafers, we present an efficiency gain of more than 1.0% absolute in cell efficiency with a peak cell efficiency of up to 20.2%. The usability of our PERC solar cells in modules is demonstrated with a 289-W module containing 60 PERC cells. To emphasize the efficacy of high-performance cells in modules, a simple cell-to-module factor calculation is presented.

Influence of Al Particle Size and Firing Profile on Void Formation in Rear Local Contacts of Silicon Solar Cells

“…The front-side emitter is covered with a silicon nitride antireflective coating and the rear surface with a standard dielectric passivation stack, consisting of a thin aluminum oxide layer capped with a silicon nitride layer, both deposited in a plasma-enhanced chemical vapor deposition system. The Line-shaped rear contact openings are formed by laser ablation [15] with a width of 20 1£111 and a pitch of 1 mm. The rear side is metalized with six different AI PERC pastes.…”

Nondestructive Characterization of Voids in Rear Local Contacts of PERC-Type Solar Cells

“…On the rear surface, a standard dielectric passivation stack, consisting of a thin aluminum oxide layer capped with a silicon nitride layer, was deposited in a PECVD system. The line-shaped contact openings on the rear side were formed by laser ablation [8]. For simplification of characterization, laser openings were made perpendicular to the front-side fingers.…”