Remote Molecular Doping of Colloidal Quantum Dot Photovoltaics

Ahmad R. Kirmani, Amirreza Kiani, Marcel M. Said, Oleksandr Voznyy, Nimer Wehbe, Grant Walters, Stephen Barlow, Edward H. Sargent, Seth R. Marder, Aram Amassian

Research output: Contribution to journalArticlepeer-review

28 Scopus citations

Abstract

In recent years colloidal quantum dot (CQD) photovoltaics have developed rapidly because of novel device architectures and robust surface passivation schemes. Achieving controlled net doping remains an important unsolved challenge for this field. Herein we present a general molecular doping platform for CQD solids employing a library of metal–organic complexes. Low effective ionization energy and high electron affinity complexes are shown to produce n- and p-doped CQD solids. We demonstrate the obvious advantage in solar cells by p-doping the CQD absorber layer. Employing photoemission spectroscopy, we identify two doping concentration regimes: lower concentrations lead to efficient doping, while higher concentrations also cause large surface dipoles creating energy barriers to carrier flow. Utilizing the lower concentration regime, we remove midgap electrons leading to 25% enhancement in the power conversion efficiency relative to undoped cells. Given the vast number of available metal–organic complexes, this approach opens new and facile routes to tuning the properties of CQDs for various applications without necessarily resorting to new ligand chemistries.
Original languageEnglish (US)
Pages (from-to)922-930
Number of pages9
JournalACS Energy Letters
Volume1
Issue number5
DOIs
StatePublished - Oct 14 2016

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