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Carbon-based top-electrodes for Hole-Transporting-Layer-free Perovskite Solar Cells (PSCs) were made by hot-press (HP) transfer of a free-standing Carbon-Aluminum foil at 100°C and pressure of 0.1MPa on a Methylammonium Lead Iodide (MAPbI3) layer. Under these conditions, the perovskite surface is preserved from interaction with the solvent. HP-PSCs have been systematically compared, along a time-scale of 90 days, to reference cells having Carbon-based top electrodes deposited by doctor blading (DB). We found that all the photovoltaic parameters recorded in HP-PSCs during time under ambient conditions settle on values systematically higher than those measured in the reference DB-PSCs, with efficiency stabilized at around 6% within the first few measurements. On the opposite side, in DB-PSCs, a long-lasting (~14 days) degrading transient of the performances is observed with a loss of efficiency from the initial ~8% to ~3%. Moreover, in the HP-PSCs a systematic day-by-day recovery of the efficiency after operation is observed (Δ~2%) by leaving the cell under open circuit, nitrogen environment and dark conditions. Noteworthily, a full recovery of all the parameters is observed at the end of the experiment while DB-PSC only shows a partial recovery at the same conditions. Hence, the complete release of solvent from the carbon contact before an interface is established with the perovskite layer offers a definite advantage through the long period of operation in preventing irreversible degradation. Our findings indeed highlight the crucial role of the interfaces in the performance restoring, especially under nitrogen atmosphere.
Publication date: 
17 Apr 2020

Salvatore Valastro, Emanuele Smecca, Salvatore Sanzaro, Ioannis Deretzis, Antonino La Magna, Youhei Numata, Ajay Kumar Jena, Tsutomu Miyasaka, Antonio Gagliano, Alessandra Alberti

Biblio References: 
Volume: 8 Pages: 200
Frontiers in chemistry