Li‐Doping and Ag‐Alloying Interplay Shows the Pathway for Kesterite Solar Cells with Efficiency Over 14

Kesterite photovoltaic technologies are critical for the deployment of light‐harvesting devices in buildings and products, enabling energy sustainable buildings, and households. The recent improvements in kesterite power conversion efficiencies have focused on improving solution‐based precursors by...

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Published in:Advanced functional materials 2024-10, Vol.34 (42), p.n/a
Main Authors: Gong, Yuancai, Jimenez‐Arguijo, Alex, Medaille, Axel Gon, Moser, Simon, Basak, Arindam, Scaffidi, Romain, Carron, Romain, Flandre, Denis, Vermang, Bart, Giraldo, Sergio, Xin, Hao, Perez‐Rodriguez, Alejandro, Saucedo, Edgardo
Format: Article
Language:English
Subjects:
Alloying
Buildings
Carrier density
Cu2ZnSn(S,Se)4
CZTSSe
Doping
Energy conversion efficiency
Energy harvesting
Grain boundaries
Grain growth
Households
kesterite solar cells
Majority carriers
molecular inks route
Optoelectronic devices
Photovoltaic cells
Precursors
Residential energy
Solar cells
Thermal stability
thin film chalcogenides
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Summary:Kesterite photovoltaic technologies are critical for the deployment of light‐harvesting devices in buildings and products, enabling energy sustainable buildings, and households. The recent improvements in kesterite power conversion efficiencies have focused on improving solution‐based precursors by improving the material phase purity, grain quality, and grain boundaries with many extrinsic doping and alloying agents (Ag, Cd, Ge…). The reported progress for solution‐based precursors has been achieved due to a grain growth in more electronically intrinsic conditions. However, the kesterite device performance is dependent on the majority carrier density and sub‐optimal carrier concentrations of 1014–1015 cm−3 have been consistently reported. Increasing the majority carrier density by one order of magnitude would increase the efficiency ceiling of kesterite solar cells, making the 20% target much more realistic. In this work, LiClO4 is introduced as a highly soluble and highly thermally stable Li precursor salt which leads to optimal (>1016 cm−3) carrier concentration without a significant impact in other relevant optoelectronic properties. The findings presented in this work demonstrate that the interplay between Li‐doping and Ag‐alloying enables a reproducible and statistically significant improvement in the device performance leading to efficiencies up to 14.1%. Incorporating Ag in kesterite materials is crucial for surpassing 13% efficiencies. However, it reduces the density of CuZn defects, resulting in a suboptimal majority carrier density near 1015 cm−3. This work provides a simple approach to tune the majority carrier density to optimal values over 1016 cm−3, leading to record‐level efficiencies above 14% and enabling efficiencies close to 20%.
ISSN:1616-301X
1616-3028
DOI:10.1002/adfm.202404669