Molecular Tailoring of Pyridine Core-Based Hole Selective Layer for Lead Free Double Perovskite Solar Cells Fabrication

To solve the toxicity issues related to lead-based halide perovskitesolar cells, the lead-free double halide perovskite Cs2AgBiBr6 is proposed. However, reduced rate of charge transferin double perovskites affects optoelectronic performance. We designeda series of pyridine-based small molecules with four different armsattached to the pyridine core as hole-selective materials by usinginterface engineering. We quantified how arm modulation affects thestructure-property-device performance relationship.Electrical, structural, and spectroscopic investigations show thatthe N (3),N (3),N (6),N (6)-tetrakis(4-methoxyphenyl)-9H-carbazole-3,6-diamine arm's robust associationwith the pyridine core results in an efficient hole extraction for PyDAnCBZ due to higher spin density close to the pyridinecore. The solar cells fabricated using Cs2AgBiBr6 as a light harvester and PyDAnCBZ as the hole selectivelayer measured an unprecedented 2.9% power conversion efficiency.Our computed road map suggests achieving & SIM;5% efficiency throughfine-tuning of Cs2AgBiBr6. Our findings revealthe principles for designing small molecules for electro-optical applicationsas well as a synergistic route to develop inorganic lead-free perovskitematerials for solar applications.