Metal halide perovskites are ideal candidates for indoor photovoltaics (IPVs) because of their easy-to-adjust bandgaps, which can be designed to cover the spectrum of any artificial light source. However, the serious non-radiative carrier recombination under low light illumination restrains the application of perovskite-based IPVs (PIPVs). Herein, polar molecules of amino naphthalene sulfonates are employed to functionalize the TiO2 substrate, anchoring the CsPbI3 perovskite crystal grains with a strong ion-dipole interaction between the molecule-level polar interlayer and the ionic perovskite film. The resulting high-quality CsPbI3 films with the merit of defect-immunity and large shunt resistance under low light conditions enable the corresponding PIPVs with an indoor power conversion efficiency of up to 41.2% (P-in: 334.11 & mu;W cm(-2), P-out: 137.66 & mu;W cm(-2)) under illumination from a commonly used indoor light-emitting diode light source (2956 K, 1062 lux). Furthermore, the device also achieves efficiencies of 29.45% (P-out: 9.80 & mu;W cm(-2)) and 32.54% (P-out: 54.34 & mu;W cm(-2)) at 106 (P-in: 33.84 & mu;W cm(-2)) and 522 lux (P-in: 168.21 & mu;W cm(-2)), respectively.