Phenylammonium Grafted SAM Molecule in Molecule-Extrusion Process to Enhance Perovskite Film Quality and Interfacial Passivation

Abstract Widely used as hole transport layers (HTLs) for inverted perovskite solar cells (PSCs), the functions of phosphonic acid-based self-assembly monolayer (SAM) molecules in the bulk of the perovskite film have been studied in a limited manner but are essential. In this work, we designed a phenylammonium-functionalized SAM molecule termed 4PACD to study its effect on the perovskite crystal growth and the interfacial defect state passivation in the bulk of the perovskite film, depending on the molecule-extrusion process. By means of in situ photoluminescence, a slower crystal growth pathway was evidenced for 4PACD-incorporated perovskite film with much improved quality, which cuts down the defect density by nearly one order. Finally, the incorporation of 4PACD resulted in a champion device power conversion efficiency (PCE) of 26.78% compared with 25.01% for the control device with 4PACD as the HTL. The target device can reserve 98.9% of the initial PCE after 1000 h of light soaking, while the control retained 88.7%. This work highlights the perovskite growth advantage of the SAM incorporated in the bulk of the perovskite film over using it only as HTL, demonstrating the great potential of the molecule-extrusion process for high-performance PSCs without predepositing HTLs.