Tri‐Step Water‐Assisted Strategy for Suppressing Cs4PbBr6 Phase in Printable Carbon‐Based CsPbBr3 Solar Cells to Achieve High Stability

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2024-11, Vol.20 (45), p.e2404044-n/a
• Main Authors: Cen, Ronghao, Shao, Wu, Wu, Wenjun
• Format: Article
• Language: English
• Subjects: all‐inorganic; Carbon; Cesium bromides; Crystal defects; Crystallization; Cs4PbBr6 Phase; Energy conversion efficiency; Ethanol; Moisture content; Perovskites; Photovoltaic cells; photovoltaic performance; printable mesoscopic perovskite solar cells; Relative humidity; Solar cells; water; Water chemistry
• ISSN: 1613-6810; 1613-6829; 1613-6829
• DOI: 10.1002/smll.202404044

Often deemed the “natural nemesis” of perovskites, water molecules have been largely circumvented by the majority of researchers in the field of perovskite solar cells. This has resulted in significant hurdles in investigating the beneficial impacts of water molecules on perovskite crystallization. Herein, it is found that by utilizing ethanol with minimal water content and subjecting all‐inorganic perovskite to three distinct annealing temperatures within the same solvent, the residual CsBr can be effectively removed, and the formation of the Cs4PbBr6 phase can be curtailed. By selecting an optimal water content, substantial improvements are observed in the crystalline quality of CsPbBr3, the perovskite/carbon interface, and the mesoporous filling effect. The Urbach energy (Eu) is reduced from 38.96 to 35.59 meV, and the defect density decreased from 4.16 × 1014 to 3.39 × 1014 cm−3. As a result, the power conversion efficiency (PCE) improved from 7.55% in the control group to 9.37%. Under severe environmental conditions with a temperature (T) of 85 °C and a relative humidity (RH) of 40%, tracking tests over 1200 h retained 89.3% of the initial PCE. This research signifies a breakthrough in the fabrication of highly stable and efficient all‐inorganic printable mesoscopic perovskite solar cells. The study innovatively integrates water into perovskite solar cell fabrication. Using ethanol with trace water and a tri‐phasic annealing technique, CsBr, suppressed Cs4PbBr6 phase formation, and enhanced CsPbBr3 crystallinity is eradicated. This led to a power conversion efficiency increase from 7.55% to 9.37%, with cells maintaining 89.3% efficiency after 1200 h under challenging conditions. This marks a significant advancement in printable mesoscopic perovskite solar cells.