'Workhorse' of photovoltaics in tandem with perovskite

Date:
February 24, 2022
Source:
Helmholtz-Zentrum Berlin fu"r Materialien und Energie
Summary:
So-called PERC cells are used in mass production of silicon
solar cells, they are considered the workhorses of photovoltaics,
dominating the market. Now two teams have shown that such standard
silicon cells are also suitable as a basis for tandem cells with
perovskite top cells.

Currently, the efficiency of the tandem cell is still below that
of optimised PERC cells alone, but could be increased to up to
29.5% through targeted optimization. The research was funded by
the German Federal Ministry of Economics as part of a joint project.



FULL STORY ========================================================================== So-called PERC cells are used in mass production of silicon solar
cells, they are considered the workhorses of photovoltaics, dominating
the market. Now two teams have shown that such standard silicon cells
are also suitable as a basis for tandem cells with perovskite top
cells. Currently, the efficiency of the tandem cell is still below that
of optimised PERC cells alone, but could be increased to up to 29.5%
through targeted optimization.


========================================================================== Tandem cells made of silicon and perovskite are able to convert the broad energy spectrum of sunlight into electrical energy more efficiently than
the respective single cells. Now, for the first time, two teams from
HZB and ISFH Hameln have succeeded in combining a perovskite top cell
with a so-called PERC/ POLO silicon cell to form a tandem device. This
is an important achievement, since PERC silicon cells on p-type silicon
are the "workhorse" of photovoltaics, with a market share of about 50%
of all solar cells produced worldwide. They are largely optimised,
long-term stable and temperature stable.

Therefore, it is particularly interesting for the commercialisation of
a perovskite-silicon tandem technology to develop a "perovskite tandem
upgrade" for PERC cells.

The team at ISFH used an industry-compatible PERC process for the backside contact of the silicon bottom cells. On the front side of the wafer,
another industrialisable technology was used, the so-called POLO contact,
which was adapted here for the small-area proof of concept cells.

The following process steps took place at HZB: A tin-doped indium
oxide recombination layer was applied as a contact between the two
subcells. On top of this, a perovskite cell was processed with a layer
sequence similar to that in the current world record tandem cell on n-type silicon heterojunction cells, made by HZB. The first perovskite PERC/POLO tandem cells produced in this way achieve an efficiency of 21.3% on an
active cell area of about 1 cm^2. This efficiency is thus still below the efficiency of optimised PERC cells in this feasibility study. "However,
initial experimental results and optical simulations indicate that we
can significantly improve the performance through process and layer optimisation," explains Dr. Lars Korte, the corresponding author of
the study.

The experts estimate the Power Conversion Efficiency (PCE) of these
perovskite/ silicon tandem solar cells with PERC-like sub-cell technology
at 29.5 %. The next steps for further efficiency increases are already
clear: Dr. Silvia Mariotti from the HZB team had identified the coverage
of the silicon surface by the perovskite as potential for improvement:
"For this purpose, one could adapt the surface of the silicon wafers and
thus quickly increase the efficiency to about 25%," says Mariotti. This
is then already significantly higher than the efficiency of PERC single
cells.

The research was funded by the German Federal Ministry of Economics as
part of a joint project. The work took place within the framework of the
joint project P3T, which is funded by the Federal Ministry of Economics
and coordinated by HZB.

========================================================================== Story Source: Materials provided by Helmholtz-Zentrum_Berlin_fu"r_Materialien_und_Energie.

Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Silvia Mariotti, Klaus Ja"ger, Marvin Diederich, Marlene S. Ha"rtel,
Bor
Li, Karl Sveinbjo"rnsson, Sarah Kajari-Schro"der, Robby
Peibst, Steve Albrecht, Lars Korte, Tobias Wietler. Monolithic
Perovskite/Silicon Tandem Solar Cells Fabricated Using Industrial
p‐Type Polycrystalline Silicon on Oxide/Passivated Emitter
and Rear Cell Silicon Bottom Cell Technology. Solar RRL, 2022;
2101066 DOI: 10.1002/ solr.202101066 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220224112608.htm

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