High Efficiency Planar p-i-n Perovskite Solar Cells Using Low-Cost Fluorene-Based Hole Transporting Material

For commercial applications, it is a challenge to find suitable and low-cost hole-transporting material (HTM) in perovskite solar cells (PSCs), where high efficiency spiro-OMeTAD and PTAA are expensive. A HTM based on 9,9-dihexyl-9H-fluorene and N,N-di-p-methylthiophenylamine (denoted as FMT) is designed and synthesized. High-yield FMT with a linear structure is synthesized in two steps. The dopant-free FMT-based planar p-i-n perovskite solar cells (pp-PSCs) exhibit a high power conversion efficiency (PCE) of 19.06%, which is among the highest PCEs reported for the pp-PSCs based on organic HTM. For comparison, a PEDOT:PSS HTM-based pp-PSC is fabricated under the same conditions, and its PCE is found to be 13.9%.