Researchers from the Indian Institute of Technology Kharagpur and the Indian Institute of Technology Delhi explain that while formamidinium (FA) and cesium (Cs)-based perovskite solar cells (PSCs) exhibit higher thermal stability, their stability under humid conditions remains a significant challenge.
In their recent study, a two-step protection approach was employed for perovskite devices using tetraoctylammonium bromide (TOAB) as a surface treatment agent and TOP-3 as a hole transport layer (HTL) to counteract adverse device degradants.
TOAB acts as a multifunctional agent by passivating trap states, imparting hydrophobicity, reducing energy mismatch between the perovskite and TOP-3 HTL, and facilitating efficient hole extraction through interactions with the HTL.
For TOAB-modified devices, the power conversion efficiency (PCE) of PSCs prepared in ambient air increased from 17.09% to 19.80%, with a notable rise in open-circuit voltage (Voc) from 1.09 V to 1.13 V.
Furthermore, under atmospheric conditions with 90% relative humidity (RH), the unencapsulated TOAB-coated devices retained over 90% of their initial PCE after 480 hours, more than 80% after 980 hours, and still maintained 67% of their initial PCE after 1200 hours. At 70% RH, similar trends were observed.
In contrast, the performance of reference devices declined rapidly within hours of storage, retaining less than 29% of their initial value after 1200 hours under the same conditions.
Additionally, the TOAB-coated devices demonstrated excellent shelf life, retaining over 80% of their initial PCE after 300 days of dark storage in air at 30% RH and approximately 74% after 400 days.
These findings highlight TOAB as a promising material for achieving efficient and moisture-stable PSCs.
