Interfacial Layer Materials with a Truxene Core for Dopant‐Free NiO<sub>x</sub>‐Based Inverted Perovskite Solar Cells
Rajarathinam Ramanujam, Hsiang‐Lin Hsu, Zhong‐En Shi, Chien‐Yu Lung, Chin‐Han Lee, Gebremariam Zebene Wubie, Chih‐Ping Chen, Shih‐Sheng Sun
Abstract
Abstract Nickel oxide (NiO x ) is commonly used as a holetransporting material (HTM) in p‐i‐n perovskite solar cells. However, the weak chemical interaction between the NiO x and CH 3 NH 3 PbI 3 (MAPbI 3 ) interface results in poor crystallinity, ineffective hole extraction, and enhanced carrier recombination, which are the leading causes for the limited stability and power conversion efficiency (PCE). Herein, two HTMs, TRUX‐D1 ( N 2 ,N 7 ,N 12 ‐tris(9,9‐dimethyl‐9 H ‐fluoren‐2‐yl)‐5,5,10,10,15,15‐hexaheptyl‐ N 2 ,N 7 ,N 12 ‐tris(4‐methoxyphenyl)‐10,15‐dihydro‐5 H ‐diindeno[1,2‐ a :1′,2′‐ c ]fluorene‐2,7,12‐triamine) and TRUX‐D2 (5,5,10,10,15,15‐hexaheptyl‐ N 2 ,N 7 ,N 12 ‐tris(4‐methoxyphenyl)‐ N 2 ,N 7 ,N 12 ‐tris(10‐methyl‐10 H ‐phenothiazin‐3‐yl)‐10,15‐dihydro‐5 H ‐diindeno[1,2‐ a :1′,2′‐ c ]fluorene‐2,7,12‐triamine), are designed with a rigid planar C 3 symmetry truxene core integrated with electron‐donating amino groups at peripheral positions. The TRUX‐D molecules are employed as effective interfacial layer (IFL) materials between the NiO x and MAPbI 3 interface. The incorporation of truxene‐based IFLs improves the quality of perovskite crystallinity, minimizes nonradiative recombination, and accelerates charge extraction which has been confirmed by various characterization techniques. As a result, the TRUX‐D1 exhibits a maximum PCE of up to 20.8% with an impressive long‐term stability. The unencapsulated device retains 98% of their initial performance following 210 days of aging in a glove box and 75.5% for the device after 80 days under ambient air condition with humidity over 40% at 25 °C.