Advances to Stabilize Photoactive Phase of <scp>FAPbI<sub>3</sub></scp> Perovskite<sup>†</sup>
Bibliographic record
Abstract
Comprehensive Summary Recently, hybrid organic–inorganic perovskite materials have drawn widespread attention because of their outstanding optoelectrical properties (i.e., high absorption coefficient, long carrier diffusion distance), hence they are suitable light‐absorbing materials for photovoltaic application. Among all perovskite materials, formamidinium lead iodide (FAPbI3) based solar cells exhibit impressive power conversion efficiency (PCE) at laboratory stage, showing great potential to compete with silicon‐based solar cell. However, FAPbI3 still suffers from poor phase stability which is the prior problem that needs to be addressed before its further commercialization. To be precise, the photoactive phase (α phase) is thermodynamically metastable at room temperature, which not only makes α phase tend to transform into photoinactive phase (δ phase), but also causes competitive crystallization between two phases during the film preparation process, making it hard to fabricate pure α‐FAPbI3 films. In our review, we summarized key factors that are vital for obtaining high‐quality FAPbI3 perovskite thin films and enhancing the stability of FAPbI3 photoactive phase. First of all, precursor solution stability is of great importance since the conditions of precursor solution determine the nucleation and crystal growth process of perovskite. By introducing coordinating additives, using FAPbI3 single crystal as raw material or applying co‐solution strategy, the impurities formed by side reaction during precursor solution aging can be effectively suppressed, thus the stability of FAPbI3 solution can be greatly prolonged. Second, the crystallization kinetics of FAPbI3 have been systematically manipulated to obtain dense and large grain size perovskite films. Through introducing intermediate phase, regulating the surface energy, and retarding the crystal growth of FAPbI3 in crystallization process, not only films without pinholes and fewer grain boundaries can be obtained, the pre‐formed δ phase at room temperature can also be well‐suppressed, thus high‐quality α‐FAPbI3 films can be obtained. Third, how to thermodynamically enhance the phase stability of acquired FAPbI3 film has been extensively studied. The Gibbs free energy of FAPbI3 photoactive phase can be reduced through composition engineering, dimension engineering and external additives engineering, hence the phase transition barrier from α phase to δ phase has been significantly improved, which further enhance the phase stability of α‐FAPbI3. Lastly, we pointed out challenges of each method and proposed potential applications of mentioned strategies on improving the stability of all kinds of perovskite materials, thus further boost the commercialization of perovskite solar cell devices.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".