SulfurPosition in Pyrene-Based PTTIs Plays a Key Role To Determine the Performanceof Perovskite Solar Cells When PTTIs Were Employed as Electron TransportLayers

In this study, two novel small organic molecules (PTTI-1 and PTTI-2, the difference between them is the position of sulfur atom in thieno[3,4-b]thiophene(TT)) are designed and synthesized through introducing the pyrene unit as the central building block and TT as the conjugated linking units. The as-prepared compounds have been demonstrated as electron transport layers (ETL) for perovskite solar cells (PSCs) and PTTI-1 shows a better power conversation efficiency (PCE) value of 15.37%, higher than that of PTTI-2 (11.07%), which may be due to the suitable energy level, strong passivation behavior, and higher electron mobility of PTTI-1. Our study clearly indicates that the sulfur position in this type of electron-transport materials plays an important role in influencing the performance of PSCs. More importantly, our devices shows decent stability, where PTTI-1-based devices retain about 83 % of its initial stability after 10 days of testing.