title: Diffusion-controlled synthesis of PbS and PbSe quantum dots with in situ halide passivation for quantum dot solar cells.
abstract: We developed a simple non-hot-injection synthetic route that achieves in situ halide-passivated PbS and PbSe quantum dots (QDs) and simplifies the fabrication of Pb-chalcogenide QD solar cells. The synthesis mechanism follows a temperature-dependent diffusion growth model leading to strategies that can achieve narrow size distributions for a range of sizes. We show that PbS QDs can be produced with a diameter as small as 2.2 nm, corresponding to a 1.7 eV band gap, while the resulting size distribution (6-7%) is comparable to that of hot-injection syntheses. The in situ chloride surface passivation is demonstrated by X-ray photoelectron spectroscopy and an improved photostability of both PbS and PbSe QDs when stored under air. Additionally, the photoluminescence quantum yield of the PbS QDs is ∼30% higher compared to the traditional synthesis. We show that PbS QD solar cells with 6.5% power conversion efficiency (PCE) can be constructed. Finally, we fabricated PbSe QD solar cells in air (rather than in inert atmosphere), achieving a PCE of 2.65% using relatively large QDs with a corresponding band gap of 0.89 eV.
authors.affiliation: School of Optical and Electronic Information, Huazhong University of Science and Technology , 1037 Luoyu Road, Wuhan, Hubei 430074, China.
authors.forename: Jianbing
authors.initials: J
authors.lastname: Zhang
authors.forename: Jianbo
authors.initials: J
authors.lastname: Gao
authors.forename: Elisa M
authors.initials: EM
authors.lastname: Miller
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Luther
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Beard