TY - JOUR
T1 - Targeted Ligand-Exchange Chemistry on Cesium Lead Halide Perovskite Quantum Dots for High-Efficiency Photovoltaics
AU - Wheeler, Lance M.
AU - Sanehira, Erin M.
AU - Marshall, Ashley R.
AU - Schulz, Philip
AU - Suri, Mokshin
AU - Anderson, Nicholas C.
AU - Christians, Jeffrey A.
AU - Nordlund, Dennis
AU - Sokaras, Dimosthenis
AU - Kroll, Thomas
AU - Harvey, Steven P.
AU - Berry, Joseph J.
AU - Lin, Lih Y.
AU - Luther, Joseph M.
N1 - Publisher Copyright:
Copyright © 2018 American Chemical Society.
PY - 2018/8/22
Y1 - 2018/8/22
N2 - The ability to manipulate quantum dot (QD) surfaces is foundational to their technological deployment. Surface manipulation of metal halide perovskite (MHP) QDs has proven particularly challenging in comparison to that of more established inorganic materials due to dynamic surface species and low material formation energy; most conventional methods of chemical manipulation targeted at the MHP QD surface will result in transformation or dissolution of the MHP crystal. In previous work, we have demonstrated record-efficiency QD solar cells (QDSCs) based on ligand-exchange procedures that electronically couple MHP QDs yet maintain their nanocrystalline size, which stabilizes the corner-sharing structure of the constituent PbI6 4- octahedra with optoelectronic properties optimal for solar energy conversion. In this work, we employ a variety of spectroscopic techniques to develop a molecular-level understanding of the MHP QD surface chemistry in this system. We individually target both the anionic (oleate) and cationic (oleylammonium) ligands. We find that atmospheric moisture aids the process by hydrolysis of methyl acetate to generate acetic acid and methanol. Acetic acid then replaces native oleate ligands to yield QD surface-bound acetate and free oleic acid. The native oleylammonium ligands remain throughout this film deposition process and are exchanged during a final treatment step employing smaller cations - namely, formamidinium. This final treatment has a narrow processing window; initial treatment at this stage leads to a more strongly coupled QD regime followed by transformation into a bulk MHP film after longer treatment. These insights provide chemical understanding to the deposition of high-quality, electronically coupled MHP QD films that maintain both quantum confinement and their crystalline phase and attain high photovoltaic performance.
AB - The ability to manipulate quantum dot (QD) surfaces is foundational to their technological deployment. Surface manipulation of metal halide perovskite (MHP) QDs has proven particularly challenging in comparison to that of more established inorganic materials due to dynamic surface species and low material formation energy; most conventional methods of chemical manipulation targeted at the MHP QD surface will result in transformation or dissolution of the MHP crystal. In previous work, we have demonstrated record-efficiency QD solar cells (QDSCs) based on ligand-exchange procedures that electronically couple MHP QDs yet maintain their nanocrystalline size, which stabilizes the corner-sharing structure of the constituent PbI6 4- octahedra with optoelectronic properties optimal for solar energy conversion. In this work, we employ a variety of spectroscopic techniques to develop a molecular-level understanding of the MHP QD surface chemistry in this system. We individually target both the anionic (oleate) and cationic (oleylammonium) ligands. We find that atmospheric moisture aids the process by hydrolysis of methyl acetate to generate acetic acid and methanol. Acetic acid then replaces native oleate ligands to yield QD surface-bound acetate and free oleic acid. The native oleylammonium ligands remain throughout this film deposition process and are exchanged during a final treatment step employing smaller cations - namely, formamidinium. This final treatment has a narrow processing window; initial treatment at this stage leads to a more strongly coupled QD regime followed by transformation into a bulk MHP film after longer treatment. These insights provide chemical understanding to the deposition of high-quality, electronically coupled MHP QD films that maintain both quantum confinement and their crystalline phase and attain high photovoltaic performance.
KW - atmospheric moisture
KW - chemical manipulation
KW - film-deposition process
KW - nanocrystalline size
KW - optoelectronic properties
KW - photovoltaic performance
KW - spectroscopic technique
KW - surface manipulation
UR - http://www.scopus.com/inward/record.url?scp=85050756214&partnerID=8YFLogxK
U2 - 10.1021/jacs.8b04984
DO - 10.1021/jacs.8b04984
M3 - Article
C2 - 30044630
AN - SCOPUS:85050756214
SN - 0002-7863
VL - 140
SP - 10504
EP - 10513
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 33
ER -