A‐D‐A‐type Molecule with Dual Functions of Efficient Charge Extraction and Trap Passivation for n‐i‐p Perovskite Solar Cells

Abstract Interfacial defects and energy level mismatches between the perovskite and 2,2′,7,7′‐tetrakis[N,N‐di(4‐methoxyphenyl)amino]‐9,9′‐spirobifluorene (Spiro‐OMeTAD) layers heavily hinder charge transfer, limiting the efficiency and stability of n‐i‐p perovskite solar cells (PSCs). Herein, D‐type TPA, D‐A‐type TPA‐CN, and A‐D‐A‐type DTPA‐CN with triphenylamine units and different interfacial dipoles are designed as multifunctional interfacial layers for n‐i‐p PSCs. Among the three molecules, A‐D‐A‐type DTPA‐CN has the largest dipole moment, hole transporting capability, and hydrophobicity, and therefore the strongest passivation of interfacial defects and the best carrier extraction efficiency can be observed. As a result, the DTPA‐CN‐treated device achieves a champion power conversion efficiency (PCE) of 25.00%, as compared to the control device (22.78%). Moreover, the long‐term stability of the unencapsulated device is significantly improved. After 2,040 h of storage in a nitrogen glove box, the device maintains over 90% of its initial efficiency, while only 61% for the control device. The work indicates that simultaneous improvement of trap passivation and hole extraction is critical for achieving highly efficient and stable n‐i‐p PSCs.