Hybrid organic–inorganic inks flatten the energy landscape in colloidal quantum dot solids

Mengxia Liu, Oleksandr Voznyy, Randy Sabatini, F. Pelayo García de Arquer, Rahim Munir, Ahmed Balawi, Xinzheng Lan, Fengjia Fan, Grant Walters, Ahmad R. Kirmani, Sjoerd Hoogland, Frédéric Laquai, Aram Amassian, Edward H. Sargent

Research output: Contribution to journalArticlepeer-review

579 Scopus citations

Abstract

Bandtail states in disordered semiconductor materials result in losses in open-circuit voltage (Voc) and inhibit carrier transport in photovoltaics. For colloidal quantum dot (CQD) films that promise low-cost, large-area, air-stable photovoltaics, bandtails are determined by CQD synthetic polydispersity and inhomogeneous aggregation during the ligand-exchange process. Here we introduce a new method for the synthesis of solution-phase ligand-exchanged CQD inks that enable a flat energy landscape and an advantageously high packing density. In the solid state, these materials exhibit a sharper bandtail and reduced energy funnelling compared with the previous best CQD thin films for photovoltaics. Consequently, we demonstrate solar cells with higher Voc and more efficient charge injection into the electron acceptor, allowing the use of a closer-to-optimum bandgap to absorb more light. These enable the fabrication of CQD solar cells made via a solution-phase ligand exchange, with a certified power conversion efficiency of 11.28%. The devices are stable when stored in air, unencapsulated, for over 1,000 h.
Original languageEnglish (US)
Pages (from-to)258-263
Number of pages6
JournalNature Materials
Volume16
Issue number2
DOIs
StatePublished - Nov 14 2016

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): KUS-11-009-21
Acknowledgements: This publication is based in part on work supported by Award KUS-11-009-21, made by King Abdullah University of Science and Technology (KAUST), by the Ontario Research Fund Research Excellence Program, and by the Natural Sciences and Engineering Research Council (NSERC) of Canada. F.P.G.d.A. acknowledges financial support from the Connaught fund. A.H.B. and F.L. thank K. Vandewal for his contribution to the photothermal deflection spectroscopy set-up and M. Baier for help with the experiments. The authors thank E. Palmiano, L. Levina, R. Wolowiec, D. Kopilovic, G. Kim and F. Fan for their help during the course of study.

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