Optimum band gap for hybrid silicon/perovskite tandem solar cell
Sketch of the tandem cell. © H. Cords/HZB
Tandem solar cells based on silicon and perovskites have raised high hopes for future high efficiency solar modules. A team led by perovskite solar cell pioneer Henry Snaith at the University of Oxford has now shown, with contributions by Bernd Rech and Lars Korte of the Helmholtz-Zentrum Berlin, that an ultimate efficiency of 30% should be attainable with such tandem cells. They discovered a structurally stable perovskite composition with its band gap tuned to an optimum value of 1.75 eV. The results have been published in "Science".
Tandem solar cells based on silicon and perovskites have raised high hopes for future high efficiency solar modules (see also results here). A tandem solar cell works by absorbing the high energy photons (visible light) in a top cell which generates a high voltage, and the lower energy photons (Infra red) in a rear cell, which generates a lower voltage. This increases the theoretical maximum efficiency by about 50% in comparison to a standalone silicon cell.
To maximise efficiency, the amount of light absorbed in top cell has to precisely match the light absorbed in the rear cell. However, the band gap of ~1.6eV of the standard perovskite material is too small to fully exploit the efficiency potential of this technology.
A team led by perovskite solar cell pioneer Prof. Henry Snaith FRS at the University of Oxford, in collaboration with silicon solar cell experts Prof. Bernd Rech and Dr. Lars Korte of the Helmholtz-Zentrum Berlin, have shown that an ultimate efficiency of 30% should be attainable with such tandem cells.
They conceived together a tandem cell, in a configuration where the perovskite and the silicon cell are mechanically stacked and contacted separately. The HZB team contributed the silicon cell. The Oxford group did vary systematically the chemical composition of the perovskite layer, and with a precise cocktail of ions discovered a structurally stable perovsksite with its band gap tuned to an optimum value of 1.75 electron volts, maintaining a high electronic quality of the layer. At the same time, they increased the chemical and thermal stability of the material significantly.
Science 8 January 2016: Vol. 351 no. 6269 pp. 151-155
A mixed-cation lead mixed-halide perovskite absorber for tandem solar cells
- Solar experts meet in BerlinThe sixth tandemPV Workshop will take place in Berlin, Germany from June 17-19, 2026, hosted by Helmholtz-Zentrum Berlin.
- AI agents deliver results – but do they reason scientifically?A research team co-led by Kevin Maik Jablonka from the Helmholtz Institute for Polymers in Energy Applications Jena (HIPOLE Jena) and N. M. Anoop Krishnan from the Indian Institute of Technology Delhi has developed Corral, a new benchmark for AI agents in science. The preprint “AI scientists produce results without reasoning scientifically” has been published on arXiv (https://doi.org/10.48550/arXiv.2604.18805). The analysis shows that current systems can execute scientific workflows and deliver results; however, they often do not follow the basic principles of scientific testing and reasoning.
- Materials chemistry shapes the future of catalysisThe synthesis of materials can serve as a tool for developing smart, adaptive electrocatalysts. This rapidly evolving field of research involves in-situ analytics, data-driven discoveries and autonomous robotics. These new approaches could accelerate the discovery of long-lasting and efficient catalysts for future energy conversion and the decarbonisation of the chemical industry. A recent article by Dr Prashanth Menezes and his team in the renowned journal Angewandte Chemie provides an overview of this research.