The article reports on the fabrication and properties of 2D (CH3(CH3)2NH3)2(CH3NH3)2n−1Pb2I3n+1 perovskite thin films, where n = 1, 2, 3, and 4. The band gaps of these compounds decrease with increasing n, from 2.24 eV for (CH3(CH3)2NH3)2PbI4 (n = 1) to 1.52 eV for CH3NH3PbI4 (n = ∞). These compounds exhibit strong light absorption in the visible region and room temperature photoluminescence, making them promising light absorbers for photovoltaic applications. The thin films of these semi-2D perovskites display ultrathin surface coverage due to the self-assembly of [Pb2I3n+1] layers perpendicular to the substrates. The authors successfully implemented these 2D perovskite materials in solid-state solar cells, achieving an initial power conversion efficiency of 4.02%, with an open-circuit voltage (Voc) of 929 mV and a short-circuit current density (Jsc) of 9.42 mA/cm2. The device retains its performance after long exposure to high humidity, demonstrating the stability of these materials. Overall, the homologous 2D halide perovskites are identified as a promising class of stable and efficient light-absorbing materials for solid-state photovoltaics.The article reports on the fabrication and properties of 2D (CH3(CH3)2NH3)2(CH3NH3)2n−1Pb2I3n+1 perovskite thin films, where n = 1, 2, 3, and 4. The band gaps of these compounds decrease with increasing n, from 2.24 eV for (CH3(CH3)2NH3)2PbI4 (n = 1) to 1.52 eV for CH3NH3PbI4 (n = ∞). These compounds exhibit strong light absorption in the visible region and room temperature photoluminescence, making them promising light absorbers for photovoltaic applications. The thin films of these semi-2D perovskites display ultrathin surface coverage due to the self-assembly of [Pb2I3n+1] layers perpendicular to the substrates. The authors successfully implemented these 2D perovskite materials in solid-state solar cells, achieving an initial power conversion efficiency of 4.02%, with an open-circuit voltage (Voc) of 929 mV and a short-circuit current density (Jsc) of 9.42 mA/cm2. The device retains its performance after long exposure to high humidity, demonstrating the stability of these materials. Overall, the homologous 2D halide perovskites are identified as a promising class of stable and efficient light-absorbing materials for solid-state photovoltaics.