Advancing Perovskite Solar Cell Development and Stability Using In-Line Electrochemical Methodologies

This talk will discuss established (spectro)electrochemistry-based measurement science approaches to quantify the distribution and energetics of donor and acceptor defects in prototypical perovskite solar cell materials and partial device stacks.<br/><br/>We utilize a solid-state electrolyte top contact that equilibrates with the perovskite film to create “half-cells” of device-relevant material stacks and study them under solar cell-relevant electric fields. This allows us to spectroscopically assess onsets in valence and conduction bands under <i>operando</i> conditions<i>,</i> as well as quantify near-band edge defects using redox-active hole or electron capturing molecular probes. The combination of spectroscopy and electrochemistry characterizes the energetic distribution of donor defect states at an energy resolution of &lt;10 meV in “stoichiometric” triple cation, mixed halide perovskite thin films (Cs0.05FA0.79 MA0.16)Pb(I0.87Br0.13)3) or CsFAMA. under device-relevant electric fields (i.e. electrochemical biasing). Limits of detection are at the 10¹⁴defects/cm³. Such detection limits are better than spectroscopic, electronic and photoemission protocols, with speciation (anion versus cation defects) not available in those other approaches.<br/><br/>The technique is exquisitely sensitive, allowing for detection of clear differences in buried perovskite/metal oxide interfaces to better understand photovoltaic performance. Ongoing efforts to characterize defects and distributions include both nickel oxide nanoparticles and sputtered nickel oxide hole-transport contacts, modified with molecular species. Advancements towards development of in-line characterization (i.e., roll-to-roll) and connections to stability will also be described and benchmarked with respect to photoluminescence and photoelectron spectroscopies.