Cooperative phase–interface modulation enabling ultralow voltage loss in bromide-containing perovskite solar cells with isopropanol as an antisolvent

Abstract

Isopropanol (IPA), as a green and low-cost antisolvent, can induce humidity-stable (111)-oriented perovskite films. However, its rapid extraction rate often leads to wrinkle formation and surface damage, while resulting in unwanted residual PbI₂. Consequently, it has been challenging to adopt IPA in inverted (p-i-n) devices, particularly for bromide-containing perovskite solar cells (PSCs). To address these issues, we developed a cooperative phase–interface modulation strategy that simultaneously optimizes both bulk and surface of Br-containing perovskite. For the first time, we reveal an IPA-driven topological correlation between the (111) orientation and δ-FAPbI₃. Leveraging this insight, the use of same umbrella-like structured IPA and isopropylammonium chloride (iPAmCl) binary additives mitigates rapid crystallization while retaining the preferred (111) orientation. Meanwhile, surface treatment with trifluoromethyl-benzylamine hydroiodide (CF₃PMAI) reconstructs the damaged surface and passivates sub-surface defects. The strong dipole effect also converts the surface from p- to n-type, forming a spontaneous p-n facet homojunction with the (111) facet bulk. Benefiting from improved energy level alignment and suppressed nonradiative recombination, the quasi-Fermi level splitting (QFLS) was effectively enhanced. As a result, a record V_OC of 1.24 V was achieved for a 1.62 eV perovskite device, with a highest PCE of 24.33% and excellent storage stability, marking the first successful application of an environmentally friendly antisolvent in Br-containing PSCs with an ultralow voltage loss of 0.38 V. This study establishes a mechanistic framework for minimizing voltage loss of high-performance PSCs.