Rational design of one-dimensional triarylamine-based covalent organic frameworks for perovskite solar cells with improved efficiency and stability.

Covalent organic frameworks (COFs) have emerged as compelling interface optimizer candidates for competent perovskite solar cells (PSCs). However, there is a notable absence of rationally designed COFs tailored for perovskite and hole transporting layers (HTLs). Herein, an unreported one-dimensional (1D) triarylamine-based covalent organic framework (COF) {[(TPA)₂(TPB)₁]_–C＝N–} with active amino groups was first synthesized. To anchor COF on the perovskite surface and manipulate the interface hole transportation, this 1D COF was salified with hydrogen halides to produce {[(TPA)₂(TPB)₁]_–C＝N–-X} (COF-X; X = Cl, Br, and I). The ammonium terminals (–NH₃⁺) can coordinate with perovskite via strong ionic interaction. The backbone units of triphenylamine (TPA) and N,N,N′,N′-tetraphenylbenzidine (TPB), renowned for their superior hole extracting and transporting properties, can enhance the hole mobility of the perovskite film from 1.02 to 3.72 cm² V⁻¹ s⁻¹. Consequently, the optimal device achieved a power conversion efficiency (PCE) of 23.58% and an impressive open-circuit voltage (V_OC) of 1.181 V. Additionally, the unencapsulated devices retained 90.8% and 89.2% of their initial efficiencies after atmospheric storage over 4800 hours and continuous illumination over 500 hours, respectively. [ABSTRACT FROM AUTHOR]