From PERC to Tandem

POLO-and p⁺/n⁺ Poly-Si Tunneling Junction as Interface between Bottom and Top Cell

authored by

Robby Peibst, Michael Rienäcker, Byungsul Min, Christina Klamt, Raphael Niepelt, Tobias F. Wietler, Thorsten Dullweber, Eduard Sauter, Jens Hubner, Michael Oestreich, Rolf Brendel

Abstract

We present a novel cell concept that combines the tandem cell approach with the passivated emitter and rear cells (PERC) mainstream technology. As an interface between Si bottom and top cell, we utilize passivating n⁺-Type polysilicon on oxide (POLO) contacts and a p⁺ poly-Si/n⁺ poly-Si tunneling junction. Our full area PERC+ Si bottom cells are fabricated within a typical industrial process sequence where the POCl₃ diffusion and SiN_x deposition are replaced by the POLO junction formation processes. The implied open-circuit voltage iV_oc that is measured on these devices reaches up to 708 mV (684 mV) under 1 sun (under filtered spectrum to simulated top cell absorption). On sister cells with planar front side, the respective iV_oc values are 718 mV (696 mV). In order to understand the device physics of our ultra-Abrupt p⁺ poly-Si/n⁺ poly-Si tunneling junction, we determined the carrier lifetime in the poly-Si by time-resolved photoluminescence. The extracted lifetimes of 42-54 ps enter as input parameter for numerical Sentaurus Device simulations. These simulations reveal the importance of band-To-band and trap-Assisted tunneling for a low tunneling junction resistivity of 2.95 m·cm². Experimentally, an upper limit for the combined junction resistance of the p⁺ poly-Si/n⁺ poly-Si/SiO_x stack of 100 m·cm² is determined.

Organisation(s)

Institute of Solid State Physics

External Organisation(s)

Institute for Solar Energy Research (ISFH)

Type

Article

Journal

IEEE Journal of Photovoltaics

Volume

9

Pages

49-54

No. of pages

6

ISSN

2156-3381

Publication date

01.2019

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Electronic, Optical and Magnetic Materials, Condensed Matter Physics, Electrical and Electronic Engineering

Sustainable Development Goals

SDG 7 - Affordable and Clean Energy

Electronic version(s)

https://doi.org/10.1109/jphotov.2018.2876999 (Access: Closed)