Influence of shell thickness and surface passivation on PbS/CdS core/shell colloidal quantum dot solar cells

Journal article

Cation-exchange has been used to synthesize PbS/CdS core/shell colloidal quantum dots from PbS starting cores. These were then incorporated as the active material in solar cell test devices using a solution-based, air-ambient, layer-by-layer spin coating process. We show that core/shell colloidal quantum dots can replace their unshelled counterparts with a similar band gap as the active layer in a solar cell device, leading to an improvement in open circuit voltage from 0.42 to 0.66 V. This improvement is attributed to a reduction in recombination as a result of the passivating shell. However, this increase comes at the expense of short circuit current by creating a barrier for transport. To overcome this, we first optimize the shell thickness by varying the conditions for cation-exchange to form the thinnest shell layer possible that provides sufficient surface passivation. Next, ligand exchange with a combination of halide and bifunctional organic molecules is used in conjunction with the core/shell strategy. Power conversion efficiencies of 5.6 ± 0.4% have been achieved with a simple heterojunction device architecture.

Authors: Neo, D; Cheng, C; Stranks, S; Fairclough, S; Kim, J

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Chemical Society
• Journal: Chemistry of Materials
• Volume: 26
• Issue: 13
• Pages: 4004-4013
• Publication date: 2014-01-01
• DOI: 10.1021/cm501595u
• EISSN: 1520-5002
• ISSN: 0897-4756