Researchers from Helmholtz Zentrum Berlin (HZB) and École Polytechnique Fédérale de Lausanne (EPFL) have presented optimization strategies for top cell processing and integration into silicon heterojunction (SHJ) bottom cells based on industrial Czochralski (Cz)-Si wafers of 140 μm thickness.
Schematic illustration of the perovskite/silicon tandem solar cell based on 140 μm Cz-Si. Image credit: ACS Applied Materials & Interfaces
The team showed that combining the self-assembled monolayer [4-(3,6-dimethyl-9H-carbazol-9-yl)butyl]phosphonic acid (Me-4PACz) with an additional phosphonic acid (PA) with different functional groups, can improve film formation when used as a hole transport layer improving wettability, minimizing shunt fraction and reducing nonradiative losses at the buried interface.
It was reported that transient surface photovoltage and transient photoluminescence measurements confirmed that the combined Me-4PACz/PA layer has similar charge transport properties to Me-4PACz alone. Based on the results of this work, a perovskite/silicon tandem solar cell with a PCE > 30% was demonstrated, highlighting the potential of 140 μm thin silicon bottom cells for industry-compatible, highly efficient tandem cells. This work demonstrates the potential for thin, double-side submicron-sized textured industry-relevant silicon bottom cells yielding a high accumulated short-circuit current density of 40.2 mA/cm2 and reaching a stabilized power conversion efficiency of >30%.
This work could pave the way towards industry-compatible, highly efficient tandem cells based on a production-compatible SHJ bottom cell.
