PERC Based Tandem Solar Cell

• HZB and ISFH have achieved 21.3% efficiency for a tandem solar cell combining perovskite and PERC/POLO silicon cell
• They used a tin-doped indium oxide recombination layer as a contact between the 2 subcells and achieved the efficiency on an active cell area of about 1 cm²
• The research team pegs the potential efficiency level of this combination to reach up to 29.5%

In what they term as the '1^st' time in the solar technology space, researchers from Hemholtz Zentrum Berlin (HZB) and the Institute for Solar Energy Research In Hamelin (ISFH) have put together a perovskite solar cell with a PERC/POLO silicon cell to make a tandem device, which they believe has the potential to reach up to 29.5% power conversion efficiency (PCE).

For their research, the team applied a tin-doped indium oxide recombination layer as a contact between the 2 subcells. On top, they processed a perovskite cell with a layer sequence similar to that it used for the 29.80% efficiency for perovskite and silicon heterojunction solar tandem cell (see 29.80% Record Tandem Solar Cell Efficiency).

The team used an industry-compatible PERC process for the backside contact of 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," they add.

They were able to achieve an efficiency of 21.3% on an active cell area of about 1 cm², which the team admits is still below the efficiency of optimized PERC cells in their feasibility study. Yet, they are confident of this efficiency to further increase to a high of 29.5%.

HZB's Dr. Silvia Mariotti identifies the coverage of silicon wafer surface by perovskite as potential for improvement to quickly increase the efficiency to about 25% which would make it significantly higher than the efficiency of PERC single cells.

Funded by the German federal Ministry of Economics as part of P3T joint project between HZB and ISFH, the project points towards the potential to develop a perovskite tandem upgrade for PERC cells as part of plans to commercialize perovskite-silicon tandem technology.

Tandem cells are not new to the solar PV world where academia, researchers and industrial set up are all trying to break the efficiency barriers and employing perovskites as top layer is a promising candidate. And combining PERC, which represents a major chunk of today's PV production, with perovskites is an interesting approach from the research group.

As PERC technology hits its practical efficiency limits, the industry is figuring out newer technologies such as heterojunction (HJT) and TOPCon among the top contenders. The possibility of perovskite & PERC combination with a high efficiency should surely excite PERC technology enthusiasts.

TaiyangNews will hold a Virtual Conference on Pushing PERC Cells to Its Limits—How to Manufacture Highest Efficiency Standard Solar Cells on March 22, 2022 to understand what the industry is doing to improve the performance of this workhorse of the solar world. Registration to the event is free and can be done here.