Layered hybrid perovskite solar cells based on single-crystalline precursor solutions with superior reproducibility

Restrained by the difficulties in the stability, crystal processing, and single-crystalline device fabrication based on the prototype perovskite of CH₃NH₃PbI₃, there is a growing interest in finding a way to introduce long-chain organic ammonium into CH₃NH₃PbI₃ to tackle these challenges, leading to emerging layered perovskite materials. Here, we first report the bulk crystal growth in an ambient atmosphere on single crystals of layered perovskite (n-C₄H₉NH₃)₂(CH₃NH₃)_n-1Pb_nI_3n+1 (n = 1, 3, and 4) obtained using fine control of the molar ratio of perovskite precursors by the top seeded solution growth (TSSG) method. The fundamental properties (band gap, PL spectra and thermal stability) of (n-C₄H₉NH₃)₂(CH₃NH₃)_n-1Pb_nI_3n+1 (n = 1, 3, and 4) single crystals are investigated. More importantly, we investigated the formation of (n-C₄H₉NH₃)₂(CH₃NH₃)_n-1Pb_nI_3n+1 (n = 3 and 4) thin films based on their single-crystalline precursors by a modified hot-casting method, which makes it easier to obtain uniformly oriented thin films to help improve the photovoltaic performance and reproducibility. And solar cells fabricated based on these thin films exhibited a power conversion efficiency (PCE) of 5.05% (n = 3) and 9.03% (n = 4), and demonstrated good feasibility and stability. These attractive results may provide an understanding for further studies of the optoelectronic device applications of these layered perovskite materials.