Improving The Performance and Stability of Perovskite Solar Cells Using Functionalised Microgels and Nanogels

Abstract

Perovskite solar cells (PSCs) have excellent optoelectronic properties and provide high power conversion efficiency (PCE). However, the poor long-term stability hinders their commercialisation. This study investigates the effects of employing poly(2-(2-methoxyethoxy) ethyl methacrylate)-co-methacrylic acid-co-ethylenegylcol dimethacrylate P(MEO2MA-MAA-EGD) nanogels (NGs) and polystyrene microgels (MGs) in PSCs. MGs and NGs are colloidal dispersions of cross-linked polymer particles, and the difference in the name is based on the difference in the size which is much smaller for the NGs. The colloidal stability of these particles and their visibility by electron microscopy techniques make them good candidates for PSCs applications. The preparation and characterisation of P(MEO2MA-MAA-EGD) NGs and polystyrene MGs are investigated in this thesis. The P(MEO2MA-MAA-EGD) NGs are introduced to the perovskite precursor as additives for the first time in this study. The results reveal that the NGs act as a passivator, stabiliser, crosslinker and adhesion promoter. Therefore, the champion PSC containing NGs has an improved PCE to 20.2% and shows remarkable stability to ambient conditions for 6 months and to elevated temperatures for 240 h. On the other hand, hydrophobic and hydrophilic polystyrene MGs are incorporated as discontinuous interlayers at electron transport layer (ETL)/perovskite interface for the first time in this study. The findings illustrate that the nature and dimensions of these particles control ion migration, non-radiative recombination, and hysteresis of the respective devices. The champion PSC containing hydrophilic MGs discontinuous interlayer has an improved PCE to 20.1%, while PSCs having the hydrophobic MGs show the lowest non-radiative recombination, ion migration, and hysteresis. This study seeks to provide fundamental understanding of the mechanisms underpinning MG- and NG-based device enhancement and contributes to the improvement of the performance and stability of PSCs using facile, potentially low cost, and scalable strategies.