Silicon heterojunction solar cell with a certified 23.1 % energy conversion efficiency
After further optimization of the baseline process for industrial silicon heterojunction (SHJ) solar cells, the accredited metrology lab ISFH CalTeC now certified an efficiency of 23.1 % for a 4 cm² solar cell. This performance is among the best in the world and demonstrates the leading role of HZB in this technology in Germany and Europe.
Within the institute PVcomB at HZB we develop SHJ cells with the focus on improving industrial applicable materials and processes in collaboration with industry partners (e.g. Meyer Burger, Von Ardenne, Singulus). Moreover, new types of solar cells with the potential to surpass the efficiency limit of silicon-based cells, such as perovskite/SHJ tandem junctions, are developed at HZB, partially in collaboration with industry (Oxford PV). Results will be presented this year at the international PV conferences WCPEC (June 10-15, Hawaii) and EUPVSEC (Sep 24-28, Brussels).
Background
Silicon heterojunction (SHJ) solar cells are made of crystalline silicon wafers using passivated contacts for both polarities based on i/n and i/p stacks of thin-film silicon alloys, such as amorphous silicon, nano-crystalline silicon or silicon oxide. Due to a high silicon wafer quality and the excellent surface passivation SHJ solar cells reach very high conversion efficiencies with highest open circuit voltages >740 mV and low temperature coefficient <0.3 %/K. With this type of two-side contacted cell Kaneka Corp. (Japan) holds the world record with a 25.1 % conversion efficiency. Recently, they attracted attention with 26.7 % for an all-rear-side contacted (IBC) SHJ cell, which is currently the world record for a silicon-based solar cell. For commercial production, the lean process sequence consisting of only four major process steps, all below <200°C processing temperature, facilitate cost-effective cell production.
- Long-term stability for perovskite solar cells: a big step forwardPerovskite solar cells are inexpensive to produce and generate a high amount of electric power per surface area. However, they are not yet stable enough, losing efficiency more rapidly than the silicon market standard. Now, an international team led by Prof. Dr. Antonio Abate has dramatically increased their stability by applying a novel coating to the interface between the surface of the perovskite and the top contact layer. This has even boosted efficiency to almost 27%, which represents the state-of-the-art. After 1,200 hours of continuous operation under standard illumination, no decrease in efficiency was observed. The study involved research teams from China, Italy, Switzerland and Germany and has been published in Nature Photonics.
- Electrocatalysis with dual functionality – an overviewHybrid electrocatalysts can produce green hydrogen, for example, and valuable organic compounds simultaneously. This promises economically viable applications. However, the complex catalytic reactions involved in producing organic compounds are not yet fully understood. Modern X-ray methods at synchrotron sources such as BESSY II, enable catalyst materials and the reactions occurring on their surfaces to be analysed in real time, in situ and under real operating conditions. This provides insights that can be used for targeted optimisation. A team has now published an overview of the current state of knowledge in Nature Reviews Chemistry.
- Successful master's degree in IR thermography on solar facadesWe are delighted to congratulate our student employee Luca Raschke on successfully completing her Master's degree in Renewable Energies at the Hochschule für Technik und Wirtschaft Berlin - and with distinction!