Modulating competitive adsorption of hybrid self-assembled molecules for efficient wide-bandgap perovskite solar cells and tandems

The employment of self-assembled molecular hybrid could improve buried interface in perovskite solar cells (PSCs). However, the interplay among hybrid self-assembled monolayers (SAMs) during the deposition process has not been well-studied. Herein, we study the interaction between co-adsorbents and commonly used SAM material, [4-(3,6-dimethyl-9H-carbazol-9-yl)butyl]phosphonic acid (Me-4PACz) for wide-bandgap (WBG) PSCs. It is found that the co-adsorbent, 6-aminohexane-1-sulfonic acid (SA) tends to fill the uncovered sites without interference with Me-4PACz, ensuring the formation of a dense hole selective layer. Moreover, the use of SA/Me-4PACz mixed SAMs could effectively reduce the interfacial non-radiative recombination loss, optimize the energy alignment at the buried interface and regulate the crystallization of WBG perovskite. As a result, the 1.77 eV WBG PSCs deliver a power conversion efficiency (PCE) of 20.67% (20.21% certified) and an impressive open-circuit voltage (VOC) of 1.332 V (1.313 V certified). By combining with a 1.26 eV narrow-bandgap (NBG) PSC, we further fabricate 2-terminal all-perovskite tandem solar cells (TSCs) with a PCE of 28.94% (28.78% certified) for 0.087 cm2 and 23.92% for mini-module with an aperture area of 11.3 cm2.