Functionalized\nSubstrates for Reduced Nonradiative\nRecombination in Metal-Halide Perovskites

Reducing nonradiative recombination is crucial for minimizing\nvoltage\nlosses in metal-halide perovskite solar cells and achieving high power\nconversion efficiencies. Photoluminescence spectroscopy on complete\nor partial perovskite solar cell stacks is often used to quantify\nand disentangle bulk and interface contributions to nonradiative\nlosses. Accurately determining the intrinsic loss in a perovskite\nlayer is key to analyzing the origins of nonradiative recombination\nand developing defect engineering strategies. Here, we study perovskite\nfilms on glass and indium–tin-oxide-covered glass substrates,\nfunctionalized with a range of different molecules, using absolute\nand transient photoluminescence. We find that grafting these substrates\nwith 1,6-hexylenediphosphonic acid (HDPA) effectively reduces the\nnonradiative losses in perovskite films for a series of perovskite\nsemiconductors with bandgaps ranging from 1.26 to 2.28 eV. The results\nsuggest that perovskites processed on HDPA-functionalized substrates\nsuffer the least from nonradiative recombination and thus approach\nthe properties of a defect-free semiconductor.