Highly Efficient and Stable GABr-Modified Ideal-Bandgap (1.35 eV) Sn/Pb Perovskite Solar Cells Achieve 20.63% Efficiency with a Record Small Voc Deficit of 0.33 V

Xianyong Zhou; Luozheng Zhang; Xingzhu Wang; Chang Liu; Shi Chen; Meiqing Zhang; Xiangnan Li; Wendi Yi; Baomin Xu

doi:10.1002/adma.201908107

Highly Efficient and Stable GABr-Modified Ideal-Bandgap (1.35 eV) Sn/Pb Perovskite Solar Cells Achieve 20.63% Efficiency with a Record Small V_oc Deficit of 0.33 V

Adv Mater. 2020 Apr;32(14):e1908107. doi: 10.1002/adma.201908107. Epub 2020 Feb 25.

Authors

Xianyong Zhou^{1

2}, Luozheng Zhang^{1

2

3}, Xingzhu Wang^{1

2

3}, Chang Liu^{1

2

3}, Shi Chen^{1

2

3}, Meiqing Zhang¹, Xiangnan Li¹, Wendi Yi¹, Baomin Xu^{1

2}

Affiliations

¹ Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen, 518055, Guangdong Province, China.
² Shenzhen Engineering Research and Development Center for Flexible Solar Cells, Southern University of Science and Technology, Shenzhen, 518055, Guangdong Province, China.
³ SUSTech Academy for Advanced Interdisciplinary Studies, Southern University of Science and Technology, Shenzhen, 518055, Guangdong Province, China.

PMID: 32100401
DOI: 10.1002/adma.201908107

Abstract

1.5-1.6 eV bandgap Pb-based perovskite solar cells (PSCs) with 30-31% theoretical efficiency limit by the Shockley-Queisser model achieve 21-24% power conversion efficiencies (PCEs). However, the best PCEs of reported ideal-bandgap (1.3-1.4 eV) Sn-Pb PSCs with a higher 33% theoretical efficiency limit are <18%, mainly because of their large open-circuit voltage (V_oc ) deficits (>0.4 V). Herein, it is found that the addition of guanidinium bromide (GABr) can significantly improve the structural and photoelectric characteristics of ideal-bandgap (≈1.34 eV) Sn-Pb perovskite films. GABr introduced in the perovskite films can efficiently reduce the high defect density caused by Sn²⁺ oxidation in the perovskite, which is favorable for facilitating hole transport, decreasing charge-carrier recombination, and reducing the V_oc deficit. Therefore, the best PCE of 20.63% with a certificated efficiency of 19.8% is achieved in 1.35 eV PSCs, along with a record small V_oc deficit of 0.33 V, which is the highest PCE among all values reported to date for ideal-bandgap Sn-Pb PSCs. Moreover, the GABr-modified PSCs exhibit significantly improved environmental and thermal stability. This work represents a noteworthy step toward the fabrication of efficient and stable ideal-bandgap PSCs.

Keywords: guanidinium bromide; ideal bandgap; mixed tin-lead perovskites; molecular doping; perovskite solar cells.

Abstract

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