A-Site Tailoring In The Vacancy-Ordered Double Perovskite Semiconductor Cs2sni6 For Photovoltaic Application

Air-stable caesium tin iodide (Cs2SnI6) double perovskite are highly desirable for substituting the lead-based halide perovskite solar cells. In this work, we have investigated the effect of A-site tailoring in Cs2SnI6 by adding monovalent cation (Rb and Ag) on film growth properties, (morphology, structural properties, optophysical properties), optoelectronic properties, and device characteristics. The crystal analysis suggests that the A-site additives suppress CsI secondary phase in (Cs1-xAx)2SnI6 film for x 0.5 whereas multiple secondary phases occur in higher additive content. The opto-physical properties reveal a small change in bandgap energy for alloyed film and excellent thermal stability in ambient air. The inverted device structure ITO/CuI/Cs2SnI6alloyed/PCBM/AZO/Ag, for the first time, demonstrated the improvement in device parameters (with VOC0.38 V and efficiency of -0.66%) for the alloyed films. The capacitance analysis reveals that the high defect density in bulk as well as at the interface (Nt 1019 cm- 3) has a deleterious effect on the device performance. In this work, we underline insight into the A-site tailoring of Cs2SnI6 double perovskite and the dominant limiting factors for getting high device performance.