Hexaazatrinaphthylene Derivatives: Efficient Electron-Transporting Materials with Tunable Energy Levels for Inverted Perovskite Solar Cells

Hexaazatrinaphthylene (HATNA) derivatives have been successfully shown to function as efficient electron‐transporting materials (ETMs) for perovskite solar cells (PVSCs). The cells demonstrate a superior power conversion efficiency (PCE) of 17.6 % with negligible hysteresis. This study provides one of the first nonfullerene small‐molecule‐based ETMs for high‐performance p–i–n PVSCs. Only sulfur has the answer: Fine tuning of the energy levels and solution processability of hexaazatrinaphthylene (HATNA) derivatives is achieved by introducing alkylsulfanyl chains of various chain lengths and with different sulfur oxidation states. Perovskite solar cells employing these HATNA derivatives as electron‐transporting materials exhibited excellent performances, with power conversion efficiencies (PCE) up to 17.6 %.