Metal organic framework derived NiO x nanoparticles for application as a hole transport layer in perovskite solar cells.

NiO x as a hole transport layer (HTL) has gained a lot of research interest in perovskite solar cells (PSCs), owing to its high optical transmittance, high power conversion efficiency, wide band-gap and ease of fabrication. In this work, four different nickel based-metal organic frameworks (MOFs) using 1,3,5-benzenetricarboxylic acid (BTC), terephthalic acid (TPA), 2-aminoterephthalic acid (ATPA), and 2,5-dihydroxyterephthalic acid (DHTPA) ligands respectively, have been employed as precursors to synthesize NiO x NPs. The employment of different ligands was found to result in NiO x NPs with different structural, optical and morphological properties. The impact of calcination temperatures of the MOFs was also studied and according to field emission scanning electron microscopy (FESEM), all MOF-derived NiO x NPs exhibited lower particle size at lower calcination temperature. Upon optimization, Ni-TPA MOF derived NiO x NPs calcined at 600 °C were identified to be the best for hole transport layer application. To explore the photovoltaic performance, these NiO x NPs have been fabricated as a thin film and its structural, optical and electrical characteristics were analyzed. According to the findings, the band energy gap ( E g ) of the fabricated thin film has been found to be 3.25 eV and the carrier concentration, hole mobility and resistivity were also measured to be 6.8 × 10 14 cm -3 ; 4.7 × 10 14 Ω cm and 2.0 cm 2 V -1 s -1 , respectively. Finally, a numerical simulation was conducted using SCAPS-1D incorporating the optical and electrical parameters from the thin film analysis. FTO/TiO 2 /CsPbBr 3 /NiO x /C has been utilized as the device configuration which recorded an efficiency of 13.9% with V oc of 1.89 V, J sc of 11.07 mA cm -2 , and FF of 66.6%.