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 language | English (US) |
|---|---|
| Pages (from-to) | 922-930 |
| Number of pages | 9 |
| Journal | ACS Energy Letters |
| Volume | 1 |
| Issue number | 5 |
| DOIs | |
| State | Published - Oct 14 2016 |
Bibliographical note
KAUST Repository Item: Exported on 2020-10-01Acknowledgements: The authors thank Yadong Zhang, Karttikay Moudgil, and Raghunath Dasari (Georgia Institute of Technology) for the chemical synthesis of the metal–organic complexes employed in this study; Dr. Omar El Tall of the Analytical Core Laboratory (KAUST) for his assistance with the absorption measurements; and Dr. Yang Yang of the Advanced Nanofabrication, Imaging and Characterization Core Lab (KAUST) for his help with PL measurements. A.R.K. also thanks Prof. Gerasimos Konstantatos, ICFO, Spain for fruitful discussions. The authors acknowledge the use of the D1 beamline at the Cornell High Energy Synchrotron Source supported by the National Science Foundation (NSF DMR-0225180) and NIH-NIGMS. The work at Georgia Institute of Technology was supported by the Office of Naval Research (N00014-14-1-0126) and the National Science Foundation (DMR-1305247).