Efficient Targeted Regulation of the Interfaces and Bulk in Inverted Perovskite Solar Cells With a...

The performance and stability of inverted perovskite solar cells (PSCs) is adversely affected by the recombination loss, ion migration, and residual stress arising from issues within the bulk and at the cathode interface. Using simple post-treatment with a novel solution-processable derivative of the dodecahydro-closo-dodecaborate anion ([closo-B₁₂H₁₂]^2-)-(TBA)₂[B₁₂H₁₁(OCH₂CH₂)₂OH] (TBA₂B)-it is simultaneously address these issues. In inverted PSCs, the cationic and anionic components of TBA₂B uniquely self-separate by positioning themselves precisely to perform their specific modification functions. The majority of [B₁₂H₁₁(OCH₂CH₂)₂OH]^2- anions reside at the (6,6)-phenyl-C₆₁ butyric acid methyl ester (PCBM)/Ag interface, which enhances the electrical and physical contact. Additionally, a substantial fraction of tetrabutylammonium cations diffuse into the perovskite/PCBM heterojunction, enabling comprehensive control over the trap passivation, stress release, ion migration elimination, and grain boundary reinforcement through the in situ formation of 1D TBAPbI₃ on the surface of the perovskite crystals. The TBA₂B devices exhibit high power conversion efficiency of 25.59% and open-circuit voltage of 1.199 V, performance that is among the highest achieved with a solution-processed perovskite/PCBM heterojunction. Furthermore, TBA₂B significantly enhances the device's stability. This study provides crucial insights into the design of efficient and solution processable [closo-B₁₂H₁₂]^2--based interface materials, and offers a comprehensive understanding of the underlying modification mechanisms.