Synergetic effects of recombination-blocking, band-bending and gap-state manipulation by interfacial engineering in solid-state DSSCs comprising Cs2SnI6 electrolyte

Here, we report the first work relating to interface-modification to solid state dye sensitized solar cells (ss-DSSCs) with Cs 2 SnI 6 electrolyte by introducing KI or guanidine thiocyanate (GuSCN). Results show that KI and GuSCN modifications endow V OC improvements of 35% and 31% respectively, leading to power conversion efficiency ( PCE ) of 5.89% and 5.64%. Although both KI and GuSCN modification can retard charge recombination, their V OC improvement mechanism is not exactly the same: KI based devices mainly enjoy up-bending of the conducting band of TiO 2 and the down shift of the gap states in Cs 2 SnI 6 , while the V OC improvement in GuSCN devices is dominated by the lowering of gap states in Cs 2 SnI 6 . Structural analysis indicates that KI/GuSCN modification causes CsSnI 3 impurity and disrupts Cs 2 SnI 6 growth at the interface, while the bulk Cs 2 SnI 6 is uninfluenced, e.g., consisting cubic Cs 2 SnI 6 particles with good crystalline. Our work provides insights for V OC improvement in ss-DSSC with interface modification in terms of electronic and material structural aspects, which enrich property-material/interface structure relationship, beneficial to both ss-DSSC architecture and material engineering.