Plasmonic Local Electric Field-Enhanced Interface toward High-Efficiency Cu₂ZnSn(S,Se)₄ Thin-Film Solar Cells

The kesterite Cu₂ZnSn(S,Se)₄ (CZTSSe) solar cells have shown a continuous rise in power conversion efficiencies in the past years. However, the encountered interfacial problems with respect to charge recombination and extraction losses at the CdS/CZTSSe heterojunction still hinder their further development. In this work, an additional plasmonic local electric field is imposed into the CdS/CZTSSe interface through the electrostatic assembly of a two-dimensional (2D) ordered Au@SiO₂ NP array onto an aminosilane-modified surface absorber. The interfacial electric properties are tuned by controlling the coverage particle distance, and the finite-difference time domain (FDTD) simulation demonstrates that the strong near-field enhancement mainly occurs near the p-n junction interface. It is shown that the imposed local electric field leads to interfacial electrostatic potential (V_elec) augmentation and improves the charge extraction and recombination processes. These electric benefits enable remarkable improvements in open-circuit voltage (V_oc) and short-circuit current (J_sc), leading to the cell efficiency being increased from 10.19 to 11.50%. This work highlights the dramatic role of the plasmonic local electric field and the use of the 2D Au@SiO₂ NP array to modify a surface absorber instead of the extensively used ion passivation, providing a new strategy for p-n junction engineering in kesterite photovoltaics.