Protic Amine Carboxylic Acid Ionic Liquids Additives Regulate α‐FAPbI₃ Phase Transition for High Efficiency Perovskite Solar Cells

Abstract

The α‐phase formamidinium lead tri‐iodide (α‐FAPbI3) has become the most promising photovoltaic absorber for perovskite solar cells (PSCs) due to its outstanding semiconductor properties and astonishing high efficiency. However, the incomplete crystallization and phase transition of α‐FAPbI3 substantially undermine the performance and stability of PSCs. In this work, a series of the protic amine carboxylic acid ion liquids are introduced as the precursor additives to efficiently regulate the crystal growth and phase transition processes of α‐FAPbI3. The MA2Pb3I8·2DMSO phase is inhibited in annealing process, which remarkably optimizes the phase transition process of α‐FAPbI3. It is noted that the functional groups of carboxyl and ammonium passivate the undercoordinated lead ions, halide vacancies, and organic vacancies, eliminating the deleterious nonradiative recombination. Consequently, the small‐area devices incorporated with 2% methylammonium butyrate (MAB) and 1.5% n‐butylammonium formate (BAFa) in perovskite show champion efficiencies of 25.10% and 24.52%, respectively. Furthermore, the large‐area modules (5 cm × 5 cm) achieve PCEs of 21.26% and 19.27% for MAB and BAFa additives, indicating the great potential for commercializing large‐area PSCs.

Recent advances in ionic molecules applied in perovskite solar cells

“…Shen et al demonstrated that during the thermal annealing of freshly prepared FAPbI 3 films, a solvate intermediate phase of MA 2 Pb 3 I 8 ·2DMSO with a needle-like morphology was initially formed. 104 With continuous annealing, the intermediate phase reacted with FAI to form α-FAPbI 3 , accompanied by the volatilization of DMSO. This crystallization process induces many small crystals and generates large areas of grain boundaries.…”

Advancing Efficiency and Stability of Lead, Tin, and Lead/Tin Perovskite Solar Cells: Strategies and Perspectives

“…A couple of years on from the first report using HP as a sensitizer in dye-sensitized solar cells, mesoporous (Gratzel and Park [76] ; Miyasaka and Snaith [77] ) and planar device structures were introduced. The device performance scaled through an array of advances based on optimizing film growth and crystallization, [78,79] solvent engineering, [4,[80][81][82][83] film composition, [5,84] additive engineering, [7,85] surface defect passivation, [86,87] and carrier transport engineering. [88][89][90] Keeping aside the device structure and crystallization approach, in this review, we discuss the strategies for bulk and interface modulation of Pb-HPSCs for simultaneous improvement in PCE and operational stability, as summarized in Table 2.…”

“…Zhong and co-workers used protic amine carboxylic acid as IL additives in the Pb-HP precursor that achieved device PCE > 25%. [135] This ionic liquid comprising the carboxyl and ammonium functional group passivates the undercoordinated lead ions, halide vacancies, and organic vacancies, eliminating the deleterious nonradiative recombination.…”

The tricyclic alkaloid catalyzed crystallization of α-FAPbI3 for high performance antisolvent-free perovskite solar cells

“…20 Moreover, the residue impurity phase resulting from the complex intermediate phase of the commonly used dimethylsulfoxide (DMSO) could lead to potential instability of the devices. 21,22 Antisolvent-free solvents are preferred for perovskite deposition while requiring extra efficient and delicate crystallization control. Solvent mixtures, such as 2-ME and CHP, 23 DMA and RNH 3 Cl ethanol, 24 and DMF and NMP, 25 incorporation with an ionic liquid, 26–28 and adjustment of the perovskite constitution 29 are reported to meditate intermediate phase and α-FAPbI 3 crystallization.…”