Complex Additive‐Assisted Crystal Growth and Phase Stabilization of α‐FAPbI₃ Film for Highly Efficient, Air‐Stable Perovskite Photovoltaics

Abstract

Solution‐processed formamidinium lead iodide (FAPbI3) perovskite is entropically metastable, and it exhibits condition‐induced crystal polymorphism. Under an ambient atmosphere, the photoactive black α‐FAPbI3 converts easily to photoinactive yellow δ‐FAPbI3. This α → δ phase degradation is further accelerated upon exposure to high temperature/humidity, directly threatening the performance and stability of perovskite solar cells (PSCs). Herein, cesium iodide‐lead iodide:dimethyl sulfoxide (CsI‐PbI2:DMSO) complex is introduced as a phase stabilizer to modulate the crystallization of α‐FAPbI3 perovskite from δ‐FAPbI3 precursor and simultaneously, serve as a defect passivator to suppress trap states formation. Theoretical simulations and experimental results reveal the pivotal role of complex additive in optimizing the energy band alignment and optoelectronic properties of α‐FAPbI3 perovskite and most importantly, hindering the α → δ phase transition. The best PSC device based on the additive‐engineered perovskite film achieves an efficiency of ≈21.9%, which is ≈11% higher than that of its pristine counterpart (≈19.8%). In addition, the incorporation of CsI‐PbI2:DMSO complex remarkably enhances the long‐term stability and photostability of the PSCs by inhibiting ion migrations and preserving the α‐phase in FAPbI3 perovskite. The additive engineering presented herein offers a route to produce FAPbI3‐based PSCs with improved performance, stability, and reproducibility.

Achieving Well-Oriented FAPbI3 Perovskite Photovoltaics by Cyclohexane Modification

“…This supports the results of the FE-SEM and XRD experiments and suggests that more photons can be absorbed in the earlier films to make additional electrons, which, in turn, form a greater current output. The value of E g , 1.53 eV (Figure b), is found to be accurate and in line with the values reported in the literature . It shows that the CHX additive did not affect the absorption edge of the FAPbI 3 layer.…”

“…The value of E g , 1.53 eV (Figure 1b), is found to be accurate and in line with the values reported in the literature. 41 It shows that the CHX additive did not affect the absorption edge of the FAPbI 3 layer. As depicted in Figure 1c, the steady-state PL profiles of all FAPbI 3 layers show a strong emission peak near the positions of their UV−vis absorption edges.…”

M13 Bacteriophage-Assisted Synergistic Optical Enhancement of Perovskite Quantum Dots

“…The simulations followed two steps: first, geometry optimizations, and second, energy calculations. The model employed a generalized gradient approximation method (GGA) based on the Perdew-Burke-Ernzerhof (PBE) function with a maximum of 300 iterations and a step size of 0.2 Å [55,56]. For structural relaxations in electronic calculations, a plane-wave cut-off of 287 eV was applied.…”

Effects of alkali metals or Cu+ addition to α-FAPbI3 perovskite crystals on electronic structures and photovoltaic properties

“…The addition of alkali elements to the precursor solutions also contributed to an increase of grain sizes and improvement of crystallinity. [29][30][31][32][33] A well-known method to improve the phase stability and device performance of FAPbI 3 is to add alkali elements, which are monovalent cations identical to FA + . While, copper compounds have been investigated as additives to perovskite precursor solutions.…”