Obtaining efficient perovskite solar modules (PSMs) with enhanced UV stability is essential for their practical applications, yet remains a significant challenge. In this work, a highly efficient organic-inorganic copper halide downshifting film that significantly enhances the UV stability of PSMs is demonstrated by converting high-energy harmful UV photons into beneficial visible light photons that contribute to photovoltaic performance. The tetrapropylammonium (TPA) cation is selected as the main framework to synthesize a series of organic-inorganic copper halides, denoted as Br