Perovskite/Silicon\nTandem Solar Cells Above 30% Conversion\nEfficiency on Submicron-Sized Textured Czochralski-Silicon Bottom\nCells with Improved Hole-Transport Layers

In perovskite/silicon tandem solar cells, the utilization\nof silicon\nheterojunction (SHJ) solar cells as bottom cells is one of the most\npromising concepts. Here, we present optimization strategies for the\ntop cell processing and their integration into SHJ bottom cells based\non industrial Czochralski (Cz)-Si wafers of 140 μm thickness.\nWe show that combining the self-assembled monolayer [4-(3,6-dimethyl-9<i>H</i>-carbazol-9-yl)butyl]phosphonic acid (Me-4PACz) with an\nadditional phosphonic acid (PA) with different functional groups,\ncan improve film formation when used as a hole transport layer improving\nwettability, minimizing shunt fraction and reducing nonradiative losses\nat the buried interface. Transient surface photovoltage and transient\nphotoluminescence measurements confirm that the combined Me-4PACz/PA\nlayer has similar charge transport properties to Me-4PACz alone. Moreover,\nthis work demonstrates the potential for thin, double-side submicron-sized\ntextured industry-relevant silicon bottom cells yielding a high accumulated\nshort-circuit current density of 40.2 mA/cm<sup>2</sup> and reaching\na stabilized power conversion efficiency of >30%. This work paves\nthe way toward industry-compatible, highly efficient tandem cells\nbased on a production-compatible SHJ bottom cell.