Enhancing NiOx Hole Transport Properties through Planarity Modulation of Organic Small Molecules for Inverted Perovskite Solar Cells
Nickel oxide (NiOx) is widely used as a hole transport material in inverted perovskite solar cells (PSCs). However, its practical application is limited by low intrinsic conductivity and insufficient hole extraction ability, leading to significant interfacial defects that reduce device efficiency and stability. To overcome these issues, two isomeric small organic molecules, 2,6-NOT and 1,5-NOT, were developed and introduced to modify NiOx. These isomers share the same structure but differ in the substitution positions of functional groups, resulting in distinct molecular planarity. Experimental results demonstrate that 1,5-NOT, featuring extended conjugation and enhanced planarity, more effectively enhances the hole extraction/transport capabilities and conductivity of NiOx compared to 2,6-NOT. The NiOx/1,5-NOT-based device achieves a remarkable power conversion efficiency (PCE) of 24.20%, along with excellent long-term stability, surpassing the NiOx control device (18.12%) and the 2,6-NOT-based device (21.87%). These findings indicate that modifying NiOx with small organic molecules significantly improves charge transport performance, and increasing molecular planarity is particularly beneficial for enhancing hole transport and reducing defect density, thereby increasing both efficiency and stability. This work provides a new strategy for NiOx modification via small organic molecules, offering a promising route to high-performance inverted PSCs.