Single-molecule dynamic dissociation and polymerization-governed in situ repair and encapsulation for high-performance perovskite solar cells

Despite the ongoing increase in the efficiency of perovskite solar cells (PSCs), residual lead iodide (PbI₂) and moisture sensitivity issues continue to constrain their further commercialization. Herein, we propose a thermally mediated in situ repair and encapsulation strategy to construct high-performance PSCs by incorporating piperazine thioctic acid salt (TAPPZ) as a dopant into the perovskite precursor. Thermally dissociated piperazine (PPZ) from TAPPZ integrates microcrystals to form larger grains (>2000 nm), while the carboxylic acid in thioctic acid (TA) and the amine salt in TAPPZ synergistically passivate and transform PbI₂, significantly reducing its residual amount. Additionally, TAPPZ undergoes thermal self-crosslinking during perovskite annealing, enabling melt-polymerization to form in situ encapsulation for enhanced water resistance. The TAPPZ-incorporated device achieves a remarkable efficiency of 25.65% and exhibits excellent operational stability, retaining over 90% of its initial efficiency after 2000 h under ambient conditions (20–30 °C, 20%–30% relative humidity). This study provides new insights into the construction of high-performance perovskite solar cells by designing and synthesizing multifunctional single molecules for in situ repair and encapsulation of perovskites.