Search

Formamidinium lead triiodide (FAPbI3) perovskite without methylammonium and/or Cs cations is considered the most promising candidate for perovskite photovoltaics. However, the crystallization of photoactive α‐FAPbI3 requires high‐temperature annealing (≥150 °C) and a controlled humidity environment when methylammonium‐containing additives are absent. A methylammonium‐free ink is reported that enables low‐temperature (≤80 °C) crystallization of photoactive α‐FAPbI3 films, while also demonstrating compatibility with blade‐coating large‐area films in ambient air. The synergistical effects of methylphenyl sulfoxide and PbCl2 facilitate the formation of an intermediate phase of nanoscale‐disordered δ‐FAPbI3, which dramatically reduces the crystallization temperature of α‐FAPbI3 down to 80 °C and even below. The 80 °C crystalized α‐FAPbI3 exhibits reduced strain and improved uniformity compared to high‐temperature annealed counterparts. The synthesized ink and the corresponding intermediate precursor film are also found remarkably stable, allowing open‐air processing without the need for humidity control. Highly efficient n–i–p structured α‐FAPbI3 minimodules can be fabricated under an ambient environment RH 50% with the ink at 80 °C, achieving a power conversion efficiency of up to 22.4%. The discovery of the low‐temperature FAPbI3 ink paves a new avenue for printing perovskite solar cells and associated optoelectronic applications, accelerating the commercialization progress of perovskite materials. [ABSTRACT FROM AUTHOR]

The preparation of pristine formamidinium lead tri‐iodide (FAPbI3) perovskite films for solar cells applications can be very challenging without methylammonium containing additives. The pinhole‐rich films prepared by methylammonium‐free approach limit the performance of the pristine FAPbI3 perovskite solar cells (PSCs). This work proposes a recrystallization method employing mixed solvent annealing (MSA) to heal the pinholes in pristine FAPbI3 perovskite films. The tetramethylene sulfoxide vapor is demonstrated most effective in grains‐merging and pinhole healing, while the addition of a secondary solvent vapor of anisole significantly improved the uniformity of TMSO vapor distribution. The pristine FAPbI3 PSCs prepared with MSA recrystallized film achieved power conversion efficiencies up to 22.43% and 16.54% on small cells (0.105 cm2) and mini‐modules (12.6 cm2), respectively, showing great potential in upscaling fabrication of perovskite photovoltaics with pristine FAPbI3. [ABSTRACT FROM AUTHOR]

Grain boundaries of metal halide perovskites contain massive defects that are detrimental to photovoltaics applications. This work demonstrates that inorganic NH4NO3 can selectively passivate the grain boundaries of perovskite films and improve their moisture resistance simultaneously, resulting in enhanced performance and stability of the methylammonium-free perovskite solar cells. [ABSTRACT FROM AUTHOR]

This article, titled "Methylammonium-Free Ink for Low-Temperature Crystallization of α-FAPbI3 Perovskite," was published in the journal Advanced Energy Materials. The authors, Tian Hou, Meng Zhang, Xiaoran Sun, Yihao Wang, Kaipeng Chen, Zhipeng Fu, Mingrui He, Xu Liu, Ziheng Liu, Yuelong Huang, Martin A. Green, and Xiaojing Hao, discuss a new method for fabricating α-FAPbI3 perovskite at low temperatures without the use of methylammonium (MA). The article includes an image illustrating the phase transition from hexagonal δ-FAPbI3 to cubic α-FAPbI3, and explains how the addition of PbCl2 and MPSO helps facilitate this transition. For more details, readers are directed to the full article. [Extracted from the article]