Gradient Doping in Sn–Pb Perovskites by Barium Ions for Efficient Single‐Junction and Tandem Solar Cells

Narrow‐bandgap (NBG) tin (Sn)–lead (Pb) perovskites generally have a high density of unintentional p‐type self‐doping, which reduces the charge‐carrier lifetimes, diffusion lengths, and device efficiencies. Here, a p–n homojunction across the Sn–Pb perovskite is demonstrated, which results from a gr...

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Published in:Advanced materials (Weinheim) 2022-04, Vol.34 (16), p.e2110351-n/a
Main Authors: Yu, Zhenhua, Chen, Xihan, Harvey, Steven P., Ni, Zhenyi, Chen, Bo, Chen, Shangshang, Yao, Canglang, Xiao, Xun, Xu, Shuang, Yang, Guang, Yan, Yanfa, Berry, Joseph J., Beard, Matthew C., Huang, Jinsong
Format: Article
Language:English
Subjects:
all-perovskite tandem solar cells
Barium
Cations
Current carriers
Doping
Energy gap
gradient n-doping by barium
homojunction
Homojunctions
Lead
Materials science
Perovskites
Photovoltaic cells
Sn-Pb perovskite solar cells
Solar cells
SOLAR ENERGY
Tin
ununiform distribution
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Summary:Narrow‐bandgap (NBG) tin (Sn)–lead (Pb) perovskites generally have a high density of unintentional p‐type self‐doping, which reduces the charge‐carrier lifetimes, diffusion lengths, and device efficiencies. Here, a p–n homojunction across the Sn–Pb perovskite is demonstrated, which results from a gradient doping by barium ions (Ba2+). It is reported that 0.1 mol% Ba2+ can effectively compensate the p‐doping of Sn–Pb perovskites or even turns it to n‐type without changing its bandgap. Ba2+ cations are found to stay at the interstitial sites and work as shallow electron donor. In addition, Ba2+ cations show a unique heterogeneous distribution in perovskite film. Most of the barium ions stay in the top 600 nm region of the perovskite films and turn it into weakly n‐type, while the bottom portion of the film remains as p‐type. The gradient doping forms a homojunction from top to bottom of the perovskite films with a built‐in field that facilitates extraction of photogenerated carriers, resulting in an increased carrier extraction length. This strategy enhances the efficiency of Sn–Pb perovskite single‐junction solar cells to over 21.0% and boosts the efficiencies of monolithic perovskite–perovskite tandem solar cells to 25.3% and 24.1%, for active areas of 5.9 mm2 and 0.94 cm2, respectively. Barium ions are reported to effectively n‐dope perovskites. Distribution of the barium ions and related n‐doping effect is in a gradient across the perovskite film, resulting in a homojunction, which facilitates the separation and transport of the photogenerated carriers. Carrier diffusion length >2 µm and boosted efficiencies of 21.2% for single‐junction cell and 25.3% for all‐perovskite tandem cell are achieved.
ISSN:0935-9648
1521-4095
DOI:10.1002/adma.202110351