Amphipathic Astaxanthin Additive for Low Voltage‐loss Perovskite Solar Cells With Enhanced Quasi‐Fermi Level Splitting and Solar Hydrogen Production Application

Abstract Even though the power conversion efficiency (PCE) of perovskite solar cells (PSCs) is nearly approaching the Schottky‐Queisser limit, low open‐circuit voltage (V oc ) and severe V oc loss problems continue to impede the improvement of PCEs. Astaxanthin (ASTA) additive is introduced in the formamidinium lead triiodide (FAPbI 3 ) perovskite film as an additive, which can facilitate the transportation of charge carriers and interact with Pb 2+ by its distinctive groupings. Furthermore, the addition of ASTA decreases the defect's active energy, regulates the deep‐level defect by filling up the grain boundaries (GBs), and promotes the crystallization of perovskite film. Remarkably, an enhanced quasi‐Fermi level splitting (QFLS) of 1.164 eV and a reduced V oc loss of only 96 mV are realized. The champion PCE of 24.56% is attained by ASTA‐modified PSCs on the basis of 22.75% PCE. Moreover, the PSCs that underwent ASTA modification demonstrate improved operational stability, ensuring consistent output in real‐world scenarios. Furthermore, PSCs with an active area of 1 cm 2 are used for water electrolysis to produce hydrogen and exhibit a PCE of 22.41%. This work offers an environmentally benign solution to address the inherent issues of FAPbI 3 PSCs and lays the groundwork for the development of a prospective solar hydrogen production application.