Screen‐printed Emitter‐Wrap‐Through solar cell with single step side selective emitter with 18.8% efficiency

Abstract

A fabrication process for Emitter‐Wrap‐Through solar cells on monocrystalline material with high quality gap passivation by wet thermal silicon dioxide is investigated. Masking and structuring steps are performed by screen‐printing technology. Via‐holes are created by an industrially applicable high‐speed laser drilling process. The cell structure features a selective emitter structure fabricated in a single high temperature step: a highly doped emitter at the via‐holes and the rear side, allowing for a low via‐hole resistivity as well as a low resistivity contact to screen‐printed pastes, and a moderately doped front side emitter exhibiting high quantum efficiency in the low wavelength range. Therefore a novel approach is applied depositing either doped or undoped PECVD silicon dioxide layers on the front side. It is shown that doping profiles advantageous for the EWT‐cell structure can be achieved. The screen‐printed aluminum paste is found to penetrate the underlying thermal dioxide layer at appropriate contact firing conditions leading to a zone of high recombination in the overlap region of aluminum and silicon dioxide. It is shown that conventional PECVD‐anti‐reflection silicon nitride acts as effective protection layer reducing the recombination in this region. Designated area conversion efficiencies up to 18.8% on FZ material are obtained applying the single step side selective emitter fabrication technique. Copyright © 2010 John Wiley & Sons, Ltd.

Analysis of Phosphorus-Doped Silicon Oxide Layers Deposited by Means of PECVD as a Dopant Source in Diffusion Processes

“…Another possibility is to use a doped silicon oxide layer as a diffusion source as shown in [13]. Such a layer can be used, as already demonstrated earlier in [14][15][16], in a co-diffusion process or to replace phosphorus oxychloride (POCl 3 ) as in [17]. Doped silicon nitride layers may also be used as a replacement for POCl 3 as shown in [18].…”

Patterned masking using polymers: insights and developments from silicon photovoltaics

“…The printed polymer can then be crosslinked either thermally or by exposure to UV light thereby enabling it to 'resist' exposure to etchants such a hydrofluoric acid (HF) or buffered oxide etch (BOE) 64 which are routinely used to selectively etch the underlying dielectric or silicon. Screen-printed resist has been used as a mask to form contact areas for metal contacts to silicon solar cells, [65][66][67] structure a dielectric layer on the rear surface to achieve selective etching or diffusion of the rear silicon surface for BC solar cells 68 and emitter wrap-through cells, 69 structure metal layers for contact separation for BC cells 65 and as plating mask. 70 Mulligan et al 70 described the use of an acid-resistant polymer, which is printed over a thin seed metal layer sputtered on the rear surface of a BC solar cell, to expose isolated metal regions each in contact with either the ntype and p-type regions of the cell.…”

Hydrothermal synthesis of Eu³⁺-doped NaYF<inf>4</inf> downconversion materials for silicon-based solar cells applications

“…Recently, alternative technologies have been examined to optimize the conversion efficiencies (CEs) of the high-efficiencies silicon-based solar cells (SBSCs), including the passivated emitter and rear cell (PERC) devices [1][2], passivated emitter and rear locally diffused (PERL) cells [3][4], passivated emitter and rear totally diffused (PERT) cells [5][6], interdigitated back-contacted (IBC) solar cells [7][8], emitter-wrap-through (EWT) solar cells [9][10] and heterojunction with intrinsic thin-layer (HIT) solar cells [11][12]. The up-and downconversion materials (DCMs) are one of the other effective methods to improve the solar cell performances [13][14][15].…”