The role of PbS QDs on strain and optical properties in different perovskite matrix

The mixture of inorganic quantum dots and hybrid perovskite in one nanocomposite is considered a favorable approach to overcome restrictions of metastable perovskite. However, to date only few examples of improved opto-electronic perovskites have been realized with such materials. Here, we show a systematic approach to characterize the standard methylammonium lead iodide (MAPbI3) perovskite system by: (i) the substitution of some MA by guanidinium (Gu); (ii) the incorporation of PbS quantum dot (QD) additives and (iii) addition of both Gu and PbS at the same time. We studied the effect of the incorporations of the big cation on the film strain and crystal cell unit volume, and on the solar cell device efficiency and stability. With the control of Gu and PbS QD content, higher performance and longer solar cell stability are obtained. PbS QDs aid Gu incorporation, resulting in an expected more stable material and devices with high amount of guanidnium. From the optical point view, the tuning of the energy levels of perovskite nanocomposite with PbS with different ligands will be also exemplified, to show that a slight shift of the energy level leads to improved efficiencies especially in the case of formamidinium/PbI2 capping ligand. With this study, we demonstrated the reason why the solar cells performances are improved up to 20%, even when the optical properties are detrimental.