Bilayer Hole-Selective Contact Enhancing Hole Extraction for Efficient Inverted Wide-Bandgap Perovskite Solar Cells

Wide-bandgap perovskite solar cells are crucial for realizing efficient tandem solar cells. However, their efficiency and stability are severely constrained by the limitations of common hole-transport materials. Conventional hole-transport materials like nickel oxide (NiO_X) suffer from high surface defect density and poor conductivity, while self-assembled monolayers (SAMs) are plagued by intrinsic shortcomings in structural and long-term stability. Herein, we propose a bilayer hole-selective contact composed of NiO_X and a 9H,9'H-[3,3'-bicarbazole]-9,9'-diylbis(butane-4,1-diyl) diphosphonic acid (DCZ) SAM molecule, which facilitates hole extraction and improves perovskite crystallization. Consequently, the champion device with a 1.77 eV perovskite achieves a PCE of 19.24% and an open-circuit voltage of 1.31 V, retaining 80% of its initial efficiency after 380 h of continuous illumination at maximum power point tracking. Furthermore, this approach could be extended to perovskite systems with bandgaps of 1.68 and 1.58 eV, delivering impressive PCEs of 22.92 and 24.93%, respectively.