Research news

Record-breaking Solar Cell

Measurement of perovskite solar cell under solar simulator at Laboratory of Photovoltaics and Optoelectronics UL FE

Photo: prof. Marko Topič, UL FE

Publish Date: 18.01.2021

Category: Outstanding research achievements, Interdisciplinary research

Sustainable development goals: 7 Affordable and clean energy, 13 Climate action (Indicators)

Solar cells and photovoltaic systems are already proving to be one of the most affordable ways to generate electricity. However, to further increase competitiveness against other sources of energy, as well as the number of solar power plants, it is crucial that the power conversion efficiency continues to grow. One way to achieve this is by using tandem solar cells, among which the perovskite/silicon tandem solar cells are the most promising in terms of affordability. This technology combines the well-established silicon solar cell technology with the new perovskite solar cells.

Slovenian researchers from the Faculty of Electrical Engineering of the University of Ljubljana participated in the development of a record-breaking perovskite/silicon tandem solar cell. The certified conversion efficiency of the tandem cell exceeded the 29 percent milestone, and the full results were published in Science.

Perovskite solar cells have seen rapid development in recent years, culminating in the publication of an article in Science ( last December, which reports a record-breaking perovskite/silicon tandem solar cell with a certified conversion efficiency of 29.15% under standard test conditions. This achievement is the result of collaboration between researchers from the Helmholtz-Zentrum Berlin (HZB) and several other institutes, including the Laboratory for Photovoltaics and Optoelectronics (LPVO) at UL FE. Asst. Prof. Marko Jošt, Dr. Gašper Matič and Prof. Marko Topič contributed to the publication.

The record-breaking cell was fabricated based on the development of an optimal layer for the transport of photogenerated holes from the cell. A carbazole-based molecule with methyl group substitution layer was used, which contributed to both excellent passivation and enhanced hole extraction from the perovskite layer. These two properties resulted in the high open-circuit voltage (1.9 V) and the high fill-factor (> 79%), and consequently record power conversion efficiency under standard test conditions. This achievement confirms the advantage of tandem solar cells, since its conversion efficiency exceeds that of any single-junction solar cell and thus represents a new milestone in solar cell conversion efficiency. In addition, the solar cell demonstrates good stability, retaining 95% of its power conversion efficiency after 300 hours of continuous operation, which promises long-term stability of operation.

The authors estimate that they will be able to produce perovskite-silicon tandem solar cells with a 32 percent power conversion efficiency in the near future, while overcoming a number of challenges. In this venture, HZB and LPVO will continue to cooperate in the framework of bilateral projects co-financed by the ARRS and the Helmholtz Gemeinschaft Deutscher Forschungszentren, the latter within the bilateral TAPAS project.

 Fotovoltaika 2

 Monolithic perovskite/silicon tandem solar cell in cross-section

Photo: Eike Köhnen from HZB (Helmholtz Center Berlin)

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