Elucidating the Role of Antisolvents on the Surface Chemistry and Optoelectronic Properties of CsPbBr<sub><i>x</i></sub>I<sub>3-x</sub> Perovskite Nanocrystals
Junzhi Ye, Zhenchao Li, Dominik J. Kubicki, Yunwei Zhang, Linjie Dai, Clara Otero‐Martínez, Manuel A. Reus, Rakesh Arul, Kavya Reddy Dudipala, Zahra Andaji‐Garmaroudi, Yi‐Teng Huang, Zewei Li, Ziming Chen, Peter Müller‐Buschbaum, Hin‐Lap Yip, Samuel D. Stranks, Clare P. Grey, Jeremy J. Baumberg, Neil C. Greenham, Lakshminarayana Polavarapu, Akshay Rao, Robert L. Z. Hoye
Abstract
NCs as the model system, which in itself is considered a promising candidate for pure-red light-emitting diodes and top-cells for tandem photovoltaics. Interestingly, we find that as the polarity of the antisolvent increases (from methyl acetate to acetone to butanol), there is a blueshift in the photoluminescence (PL) peak of the NCs along with a decrease in PL quantum yield (PLQY). Through transmission electron microscopy and X-ray photoemission spectroscopy measurements, we find that these changes in PL properties arise from antisolvent-induced iodide removal, which leads to a change in halide composition and, thus, the bandgap. Using detailed nuclear magnetic resonance (NMR) and Fourier-transform infrared spectroscopy (FTIR) measurements along with density functional theory calculations, we propose that more polar antisolvents favor the detachment of the oleic acid and oleylamine ligands, which undergo amide condensation reactions, leading to the removal of iodide anions from the NC surface bound to these ligands. This work shows that careful selection of low-polarity antisolvents is a critical part of designing the synthesis of NCs to achieve high PLQYs with minimal defect-mediated phase segregation.