With an externally verified efficiency of 29.15 percent, researchers at the Helmholtz Zentrum Berlin (HZB), along with colleagues from Kaunas University of Technology, have assembled a record-breaking silicon-perovskite solar cell. The previous record of 28 percent was held by British-German startup Oxford PV.
Most of the improvement was realized by tweaking material composition and improving fabrication techniques. A new element, however, was a self-assembling monolayer (SAM) as a hole transport layer. SAMs are formed simply by dipping the substrate in a solution, allowing dissolved molecules to anchor themselves to the surface. The resulting layer is as thin (1-2 nanometer) as the cross-section of the molecules involved.
The researchers are confident they can push through the 30 percent efficiency barrier. The practical efficiency limit of silicon-perovskite tandem cells is about 35 percent.