Emitter saturation current densities of 22 fA/cm² applied to industrial PERC solar cells approaching 22% conversion efficiency

verfasst von

Thorsten Dullweber, Helge Hannebauer, Silke Dorn, Sabrina Schimanke, Agnes Merkle, Carsten Hampe, Rolf Brendel

Abstract

Passivated Emitter and Rear Cells (PERC) are currently being introduced into mass production. The conversion efficiency of industrial p-type PERC cells is limited by the emitter saturation current density of around 90 fA/cm² of conventional homogeneously POCl₃ diffused emitters. In this paper we investigate two alternative emitter formation technologies. The first approach named in-situ oxidation inserts a short thermal oxidation in-between the phosphorus silicate glass deposition and the drive-in of a conventional homogeneous POCl₃ diffusion thereby reducing the phosphorus surface concentration. The second approach named Gas Phase Etch Back (GEB) selectively removes around 40 nm of the highly doped surface of the POCl₃ diffused emitter by the reactive gas phase of the wet chemical rear polishing bath. Whereas the conventional POCl₃ emitter exhibits a phosphorus surface doping concentration of 3 × 10²⁰ cm⁻³, the in-situ oxidation and the GEB process reduce the doping concentration to 7 × 10¹⁹ cm⁻³ and 4 × 10¹⁹ cm⁻³, respectively. Accordingly, the emitter saturation current density is reduced to excellent values of 22 fA/cm² (in-situ oxidation) and 28 fA/cm² (GEB) compared with 89 fA/cm² for the reference POCl₃ diffusion. Whereas the reference POCl₃ emitter limits the PERC conversion efficiency η to 21.1% and the open circuit voltage V_oc to 655 mV, the in-situ oxidation improves the PERC current–voltage parameters up to 21.3% and 663 mV. The highest efficiency of 21.6% is obtained with the selective GEB emitter. When solving series resistance issues with the most advanced GEB emitter, the measured V_oc and J_sc values would support PERC conversion efficiencies up to 21.9%.

Organisationseinheit(en)

Abt. Solarenergie

Externe Organisation(en)

Institut für Solarenergieforschung GmbH (ISFH)

Typ

Artikel

Journal

Progress in Photovoltaics: Research and Applications

Band

25

Seiten

509-514

Anzahl der Seiten

6

ISSN

1062-7995

Publikationsdatum

07.2017

Publikationsstatus

Veröffentlicht

Peer-reviewed

Ja

ASJC Scopus Sachgebiete

Elektronische, optische und magnetische Materialien, Erneuerbare Energien, Nachhaltigkeit und Umwelt, Physik der kondensierten Materie, Elektrotechnik und Elektronik

Ziele für nachhaltige Entwicklung

SDG 7 – Erschwingliche und saubere Energie

Elektronische Version(en)

https://doi.org/10.1002/pip.2806 (Zugang: Geschlossen)