Moisture-Stable FAPbI₃ Perovskite Achieved by Atomic Structure Negotiation

Abstract

Broad impact in the research community may be anticipated when a material's properties are capable of being manipulated artificially. Such a possibility has been explored here in the FAPbI 3 perovskite structure of perovskite solar cells, which involves undesirable phase transition at working temperature, despite many attempts to resolve the issue. Essential steps have been taken here toward solving this problem by adopting an opposite strategy to incorporate the water molecules into the perovskite structure under the current materials framework by new structural physics maneuvering. The secondary bonding of the perovskite structure has been relocated, which altered the microstructure to remove the internal strain that caused the phase transition, resulting in not only a 10-fold enhancement in the moisture/structure stability but also a bandgap comparable to that of the favored α-FAPbI 3 . All this opens an unprecedented avenue in perovskite research, which will hopefully be of intrinsic interest to the broad materials research community as well.

The influence of compression on the lattice stability of α-FAPbI3 revealed by numerical simulation

“…35 The calculated activation energy under no stress was close to the literature value of 0.7 eV. 14,35 to become E a -Sm-Bd E Ã a À Á…”

“…Such a result proved the beneficial effect of temperature on the perovskite stability, as has been predicted by the phase map of FAPbI 3 . 14 The iteration number needed for the completion of the phase transition under compression was also increased from 30 to 34. Therefore, the structural ''lifetime'' can be increased at 85 1C by the lowered Gibbs free energy of the a phase, as shown in Fig.…”

“…[8][9][10][11] However, the desired phase of FAPbI 3 (a-FAPbI 3 ) is not stable in the air at room temperature, and spontaneously transforms into a high bandgap phase (d-FAPbI 3 ) within several minutes, 12,13 placing a severe hindrance on commercialization. Even worse, other factors aggravate this problem, such as water moisture [14][15][16] and residue tensile strain in the perovskite films. 12,[17][18][19] Much effort has been devoted to resolving the moisture problem, including doping, 20,21 encapsulation, 22 and interface engineering.…”

“…12,[17][18][19] Much effort has been devoted to resolving the moisture problem, including doping, 20,21 encapsulation, 22 and interface engineering. 23,24 Among the trials, an important step forward was achieved recently, when a stable hydrate phase of FAPbI 3 was discovered, 14 providing an effective solution to this problem, which leaves residue tensile strain as the only challenge remaining. The residue tensile strain generated during the annealing process accelerates the breakdown of the cubic structure of a-FAPbI 3 , which is attributed to the oversized FA ions located in the cubic center.…”

Probing Surface Information of Alloy by Time of Flight-Secondary Ion Mass Spectrometer

“…Solar cells based on hybrid perovskite have been considered as one of the most promising candidates for next generation of photovoltaics [1][2][3]. However, perovskite solar cells exhibited instability problems even under encapsulation [4][5][6][7], i.e., the surface of function layer began to degrade within only hundreds of hours, which limited their practical applications. To resolve this, understanding the degradation mechanism at the surface and improving its stability become imperative and important [8,9].…”