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Trap‐State Suppression and Improved Charge Transport in PbS Quantum Dot Solar Cells with Synergistic Mixed‐Ligand Treatments
Author(s) -
Pradhan Santanu,
Stavrinadis Alexandros,
Gupta Shuchi,
Bi Yu,
Di Stasio Francesco,
Konstantatos Gerasimos
Publication year - 2017
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.201700598
Subject(s) - quantum dot , trap (plumbing) , charge (physics) , materials science , optoelectronics , multiple exciton generation , ligand (biochemistry) , charge carrier , nanotechnology , chemical physics , chemistry , physics , quantum mechanics , biochemistry , receptor , meteorology
The power conversion efficiency of colloidal PbS‐quantum‐dot (QD)‐based solar cells is significantly hampered by lower‐than‐expected open circuit voltage ( V OC ). The V OC deficit is considerably higher in QD‐based solar cells compared to other types of existing solar cells due to in‐gap trap‐induced bulk recombination of photogenerated carriers. Here, this study reports a ligand exchange procedure based on a mixture of zinc iodide and 3‐mercaptopropyonic acid to reduce the V OC deficit without compromising the high current density. This layer‐by‐layer solid state ligand exchange treatment enhances the photovoltaic performance from 6.62 to 9.92% with a significant improvement in V OC from 0.58 to 0.66 V. This study further employs optoelectronic characterization, X‐ray photoelectron spectroscopy, and photoluminescence spectroscopy to understand the origin of V OC improvement. The mixed‐ligand treatment reduces the sub‐bandgap traps and significantly reduces bulk recombination in the devices.