Wide-bandgapperovskites play a key role in high-performancetandemsolar cells, which have the potential to break the Schockley-Queisserlimit. Here, a 2D/3D hybrid wide-bandgap perovskite was developedusing octane-1,8-diaminium (ODA) as spacer. The incorporation of theODA spacer can not only significantly reduce charge carrier nonradiativerecombination loss but also inhibit phase separation. Moreover, witha synergy effect using butylammonium iodide (BAI) as a surface defectpassivator, both the phase stability and device performance were furtherimproved. Compared to the control inverted device with a V (OC) of 1.16 V and a PCE of 18.50%, the optimized PSCs basedon a surface processed 2D/3D perovskite exhibit a superior high V (OC) of 1.26 V and a champion PCE of 22.19%, whichis a record efficiency for wide-bandgap PSCs (E (g) > 1.65 eV). This work provides a very effective strategyto suppress phase separation in wide-bandgap perovskites for highlyefficient and stable solar cells.