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Formation of a nanoporous PbI2 layer framework via 4‐tBP additive to improve the performance and stability of two‐step prepared hybrid perovskite solar cells under ambient conditions

Perovskite solar cells (PSCs) exhibit exceptional photovoltaic properties but low stability in ambient conditions. Today, the use of the hydrophobic 4‐tert‐butylpyridine (4‐tBP)‐based additive is accepted as an effective path to overcome such vulnerability. In this work, we use 4‐tBP as the lead iodide (PbI2) precursor solution additive to obtain volumetrically nanoporous PbI2 films with an average pore size of 10 nm. The obtained nanoporous PbI2 films enhance the diffusion of the methylammonium iodide/chloride (MAI/MACl) molecules into the PbI2 framework, obtaining perovskite (CH3NH3PbI3−xClx‐based) films with larger and interpenetrated grains. Improvements in crystallinity, homogeneity, and surface morphology, as well as a power conversion efficiency (PCE) increment in the PSCs deposited by the two‐step method, are observed when 4‐tBP is added. The best performance achieved corresponds to the PbI2•4‐tBP‐based PSC prepared with 120 μL of 4‐tBP and 0.06 M MAI, which shows Jsc = 23.02 mA cm−2, Voc = 0.99 V, FF = 0.69, and PCE = 15.83%. Likewise, this PSC retains approximately 90% of its original PCE compared to the 80% retained by the reference PSC without 4‐tBP. It is demonstrated that 4‐tBP as an additive, modifies the PbI2 precursor solution, enhancing the physical properties of the perovskite films, in addition to improved stability and PCE of the PSCs under ambient conditions compared with those devices prepared without 4‐tBP.