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.