Methylamine-Dimer-Induced Phase Transition toward MAPbI₃ Films and High-Efficiency Perovskite Solar Modules

Abstract

Perovskite films prepared with CH3NH2 molecules under ambient conditions have led to rapid fabrication of perovskite solar cells (PSCs), but there remains a lack of mechanistic studies and inconsistencies with operability in their production. Here the crystal structure of CH3NH2–CH3NH3PbI3 was analyzed to involve hydrogen bonds (CH3NH2···CH3NH3 +) and has guided the facile, reproducible preparation of high-quality perovskite films under ambient conditions. Hydrogen bonds within CH3NH2···CH3NH3 + dimers were found in the CH3NH2–CH3NH3PbI3 intermediates, accompanied by 1D-PbI3 – chains (δ-phase). The weakly hydrogen-bonded CH3NH2 molecules were easily released from the CH3NH2–CH3NH3PbI3 intermediates, contributing to rapid, spontaneous phase transition from 1D-PbI3 – (δ-phase) to 3D-PbI3 – (α-phase). Further introduction of CH3NH3Cl into the CH3NH2–CH3NH3PbI3 intermediates led to interruption of 1D-PbI3 – transition into 0D-Pb2I9‑x Cl x 5–(0 < x < 6), adjusting the phase transition route toward 3D-PbI3 –. On the basis of the above understanding, CH3NH2 solution in ethanol and CH3NH3Cl were used for precursors and a best efficiency of 20.3% in PSCs was achieved. Large-scale modules (12 cm2 aperture area) fabricated by a dip-coating technology exhibited an efficiency up to 16.0% and outstanding stability over 10 000 s under continuous output. The developed preparation method of perovskite precursors and insightful research into the methylamine-dimer-induced phase transition mechanism have enabled the production of high-quality perovskite films with robust operability, showing great potential for large-scale commercialization.

Understanding the precursor chemistry for one-step deposition of mixed cation perovskite solar cells by methylamine route

“…This observation is contrary to typical solvents (DMSO or DMF), where the iodoplumbate complexation solely determine the phase crystallization [55,56]. Recently, similar observation of formation of 1D phases upon MA exposure in MAPbI 3 perovskite has been reported [24], supporting our results.…”

“…Using this precursor, the drawbacks mentioned above have been overcome, allowing one-step deposition of perovskite films with optimal morphology over large area substrates. The advantage of this precursor relies on the strong coordination interaction of MA with PbI 6 À clusters combined with hydrogen bonding with the CH 3 NH 3 + (MA + ) cations at A-sites of the MAPbI 3 perovskite [24][25][26][27][28]. As a result, stable solutions of MAPbI 3 in mixed solvents including MA/ACN [29] and MA/ Tetrahydrofuran (THF) [30] has been reported.…”

Ambient Fabrication of Organic–Inorganic Hybrid Perovskite Solar Cells

“…Also, MAPbI 3 -agarose complexes passivated the grain boundaries and provided continuous carrier transporting pathways. Huang et al [185] used MA solution in ethanol and MACl as the additives in the perovskite fabrication under ambient condition (RH 10-15%). During their preparation of MAPbI 3 films, the presence of weak hydrogen bonding within the CH 3 NH 2 -CH 3 NH 3 + dimers, whereby dissociation of CH 3 NH 2 from the intermediate encouraged a fast, spontaneous phase transition of the intermediate/ perovskite from δ-MAPbI 3 to α-MAPbI 3 .…”

Historical Analysis of High‐Efficiency, Large‐Area Solar Cells: Toward Upscaling of Perovskite Solar Cells

“…Wet process [52][53][54] Dry process Hybrid (wet + dry) process [38] Single step Spin-coating [44,47,55,56] Drop-casting [57] Blade-coating [58][59][60][61] Slot-die-coating [62,63] Spray-coating [64] Meniscus-coating [65] Soft cover deposition [66] Dip-coating [67] Coevaporation [68,69] Chemical vapor deposition (CVD) [70] Double step Sequential deposition [43] Interdiffusion spin-coating [71] Combinations of Evaporation + evaporating [72] Evaporation + CVD [73] Sputtering + CVD [74] Sputtering + direct contact [51] Evaporation + CVD [75] Sputtering + vapor annealing [76] Combinations of Spin-coating + vapor annealing [77] Evaporation + spin-coating [78] Sputtering + dipping [79] Spin-coating + CVD [80] Figure 2. Parameters of large-area perovskite solar cells according to the process, number of components, and area.…”