Charge Carrier Dynamics\nat the Perovskite Interface\nwith Self-Assembled Monolayers

Self-assembled monolayers (SAMs) deposited on the hole-collecting\nelectrodes of p–i–n perovskite solar cells effectively\nreplace bulky hole transporting layers. However, the mechanism by which monolayers control the electronic\nprocesses and how they depend on the properties of the monolayer molecules\nremain poorly understood. In this study, we developed a simplified\nperovskite solar cell imitator with blocked electron extraction to\ninvestigate the photocurrent dynamics between the perovskite and the\nhole-collecting ITO electrode. We investigated the photoluminescence\nand photovoltage dynamics under short laser pulse excitation and addressed\nthe influence of bulky and monomolecular hole transport layers. Our\nfindings reveal that the photovoltage dynamics is significantly affected\nby the properties of the transport and perovskite layers, which in\nturn depend on the methods of sample preparation and exploration.\nPhotocurrent dynamics is determined by several processes, including\ncharge carrier displacement in the local electric field, hole transport\nto ITO, trapping of holes in interface trap states, and electron–hole\nrecombination at the interface. We propose a model that takes into\naccount molecular dipole moments and their ionization potentials to\npartially explain the different influences of different monolayers\non the hole extraction and interfacial recombination rates. Additionally,\nthe photovoltage dynamics also strongly depends on the illumination\nof the sample and shows memory effects that persist over minutes and\nhours and are attributed to the redistribution of ions.