High performance of PbSe/PbS core/shell quantum dot heterojunction solar cells: short circuit current enhancement without the loss of open circuit voltage by shell thickness control. Issue 41 (6th October 2015)

• Record Type: Journal Article
• Authors: Choi, Hyekyoung; Song, Jung Hoon; Jang, Jihoon; Mai, Xuan Dung; Kim, Sungwoo; Jeong, Sohee
• Is Part Of: Nanoscale. Volume 7:Issue 41(2015)
• Page Start: 17473
• Page End: 17481
• Publication Date: 2015-10-06
• Subjects: Nanoscience -- Periodicals; Nanotechnology -- Periodicals; 620.505
• DOI: 10.1039/c5nr03309h
• Languages: English
• ISSNs: 2040-3364

Abstract

Abstract : PbSe/PbS core/shell quantum dot solar cells are fabricated. Short circuit current increases as PbS shell thickness without loss of open circuit voltage. Abstract : We fabricated heterojunction solar cells with PbSe/PbS core shell quantum dots and studied the precisely controlled PbS shell thickness dependency in terms of optical properties, electronic structure, and solar cell performances. When the PbS shell thickness increases, the short circuit current density ( J SC ) increases from 6.4 to 11.8 mA cm −2 and the fill factor (FF) enhances from 30 to 49% while the open circuit voltage ( V OC ) remains unchanged at 0.46 V even with the decreased effective band gap. We found that the Fermi level and the valence band maximum level remain unchanged in both the PbSe core and PbSe/PbS core/shell with a less than 1 nm thick PbS shell as probed via ultraviolet photoelectron spectroscopy (UPS). The PbS shell reduces their surface trap density as confirmed by relative quantum yield measurements. Consequently, PbS shell formation on the PbSe core mitigates the trade-off relationship between the open circuit voltage and the short circuit current density. Finally, under the optimized conditions, the PbSe core with a 0.9 nm thick shell yielded a power conversion efficiency of 6.5% under AM 1.5.