Perovskite’s Additives: a General Assessment Strategy Towards Stable p-i-n Device
Creators: name: Castriotta, Luigi Angelo
name: Di Giacomo, Francesco
name: Calabrò, Emanuele
name: Harshavardan, Reddy Sathy
name: Takhellambam, Daimiota
name: Di Carlo, Aldo
Publisher: name: figshare
Year: 2021
Subjects: subject: 91305 Energy Generation, Conversion and Storage Engineering
subject: FOS: Mechanical engineering

description: During the last few years research community have been interested in studying Perovskite materials, a brilliant semiconductor with excellent charge mobilities that has the capability to tune the bandgap, to be deposited by low temperature (below 100°C) and by solution-processable techniques, lowering the actual production cost of its Silicon counterpart, and also widening the potential application of this material from standard Perovskite Solar Farm to Tandem thin film application, Building Integrated Photovoltaics (BIPV), Building Applied Photovoltaics (BAPV), e-Mobility and Internet of Things (IoT). Perovskite solar technology has become a trending topic in the last decade, reaching promising efficiencies up to 25.5%. Researchers mainly focused on obtaining high results instead of caring about stability measurements over time using standard stress test conditions, such as thermal and light soaking stressing tests. Only in 2020, an interlaboratory effort among more than 50 researchers agreed on standardizing stability measurements for Perovskite Solar Cells, recognising the importance to address the research in this channel in order to be heard by investors, stake holders and by the rest of the population, so that our effort can have a major effect in the coming years, with the final aim of lowering the CO2 consumption worldwide, as stated in the Sustainable Development Goals of the United Nations by 2030. For this reason, we conducted our work taking into account the integrated lifetime energy yield (LEY), a fundamental parameter to check the performances of a device over time. We started by studying a standard triple cation perovskite, with the presence of Methylammonium (MA), Formamidinium (FA) and Caesium (Cs) as cations, Iodide (I) and Bromide (Br) as anions, in a combination to form a narrow bandgap active material (~1.55eV) suitable for single-junction device. We then move towards wider bandgap materials (~1.63eV) suitable for tandem application with the scope of finding a common strategy to build a robust device stable over time independently on the perovskite used. In order to improve the intrinsic stability of the perovskite layer, we focused on the perovskite precursors first, such as the excess of PbI2 and the addition of FACl, well known to be used to increase the device performances, and the removal of MA cation, the most volatile material easy to degases, who is one of the main responsible of accelerating intrinsic degradation. We finally combine all these engineering approaches by inserting ionic liquids first, such as 1-Butyl-3-methylimidazolium tetrafluoroborate (BMIM-BF4) alkylamine ligands, such as Oleylamine (Oam), studying their effects at different trace amounts separately and together. Our work reveals that the excess of PbI2 and the presence of FACl shows lower LEY with respect to their reference without any precursors additives, whereas the removal of MA in the perovskite crystal indeed improves LEY values with the presence of BMIM-BF4 and OAm. As a final remark of our study, we upscaled the best combination of additives in the perovskite, giving us the better LEY, showing exciting ISOS-T1 and ISOS-L1 test results.