TY - JOUR

T1 - From PERC to Tandem

T2 - POLO-and p+/n+ Poly-Si Tunneling Junction as Interface between Bottom and Top Cell

AU - Peibst, Robby

AU - Rienäcker, Michael

AU - Min, Byungsul

AU - Klamt, Christina

AU - Niepelt, Raphael

AU - Wietler, Tobias F.

AU - Dullweber, Thorsten

AU - Sauter, Eduard

AU - Hubner, Jens

AU - Oestreich, Michael

AU - Brendel, Rolf

N1 - Funding information: This work was supported in part by the German Federal Ministry for Economic Affairs and Energy, under Grant 324040 (Project EASi), in part by the Federal Sate of Lower Saxony, and in part by the European Union’s Horizon 2020 Programme for Research, Technological Development and Demonstration under Grant 727529 (Project DISC).

PY - 2019/1

Y1 - 2019/1

N2 - 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 SiNx deposition are replaced by the POLO junction formation processes. The implied open-circuit voltage iVoc 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 iVoc 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/SiOx stack of 100 m·cm2 is determined.

AB - 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 SiNx deposition are replaced by the POLO junction formation processes. The implied open-circuit voltage iVoc 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 iVoc 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/SiOx stack of 100 m·cm2 is determined.

KW - p-Type silicon cell

KW - Passivated emitter and rear cells (PERC)

KW - passivating contacts

KW - photoluminescence

KW - photovoltaic cells

KW - polycrystalline silicon

KW - silicon-based tandem solar cells

KW - solar energy

KW - tunneling junction

UR - http://www.scopus.com/inward/record.url?scp=85056574437&partnerID=8YFLogxK

U2 - 10.1109/jphotov.2018.2876999

DO - 10.1109/jphotov.2018.2876999

M3 - Article

AN - SCOPUS:85056574437

VL - 9

SP - 49

EP - 54

JO - IEEE Journal of Photovoltaics

JF - IEEE Journal of Photovoltaics

SN - 2156-3381

IS - 1

M1 - 8533392

ER -