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Page 6 of 34 Wang et al. Energy Mater. 2026, 6, 600064

growth phase, PTCoPF actively suppresses secondary nucleation events and enhances overall crystallinity
6
[Figure 1C]. Ultimately, this seamless transition from uniform nucleation to carefully regulated crystal
growth minimizes structural defects across all energy levels and establishes a robust foundation for superior
device performance.

Collectively, the deployment of molecular additives transforms perovskite crystallization from a stochastic
process into a precisely programmable pathway. This comprehensive regulatory paradigm systematically
orchestrates three interdependent stages comprising colloidal stabilization, intermediate phase engineering,
and kinetic growth control. Navigating these stages requires a careful reconciliation of inherent mechanistic
trade-offs to ensure that suppressing one defect pathway does not inadvertently induce another. By
successfully balancing these competing kinetic and thermodynamic demands, researchers can produce
highly crystalline and defect-lean films necessary for scalable device fabrication. Moving forward, the
evolution of additive engineering will increasingly rely on the rational design of multisite molecules.
Compounds equipped with diverse coordinating groups possess the unique capability to govern the entire
crystallization sequence from precursor homogenization to grain boundary passivation. To accelerate the
discovery of such molecules, the integration of ML and high-throughput computational screening will be
essential. These data-driven algorithms offer a powerful approach to explore vast chemical spaces and predict
novel candidates that optimally satisfy the complex trade-offs across all three crystallization phases.
Ultimately, coupling predictive computational models with targeted multisite additive synthesis will establish
a robust foundation for the commercialization of highly efficient and reproducible perovskite
optoelectronics.

Defect-selective passivation for targeted mitigation
In an ideal perovskite crystal, each constituent ion occupies its thermodynamically stable lattice site.
However, in practice, the rapid crystallization kinetics of perovskite thin films, typically accompanied by
post-deposition annealing, often lead to non-equilibrium conditions that inevitably result in the formation of
diverse structural defects . As illustrated in Figure 2, in polycrystalline films, these defects are typically
[59]
categorized into point defects [60,61] , surface, grain boundary, and interface defects [62-64] , and extended defects
such as secondary phases [65,66] . Each defect class introduces distinct electronic trap states that impair carrier
dynamics by promoting non-radiative recombination, reducing carrier lifetimes, and limiting charge
transport. Additive engineering has thus emerged as a highly versatile strategy for selectively passivating
these diverse defect types across multiple length scales. A deep understanding of these defect-passivation
mechanisms not only enables performance enhancement but also lays the essential groundwork for the
integration of data-driven approaches, such as machine learning, in the rational design of next-generation
perovskite optoelectronic materials.

Point defects
Among the most fundamental are point defects, which originate from atomic-scale deviations in
stoichiometry or coordination and serve as primary sources of deep-level trap states. Point defects in halide
perovskites, including anion vacancies (V , V ) [67-69] , cation vacancies (V , V , V ) [70-72] , and antisite defects
I
Cs
FA
Br
MA
(e.g., I , Pb ) [73-75] , introduce deep-level trap states that accelerate Shockley-Read-Hall (SRH) recombination
I
Pb
and thereby restrict device efficiency. Additive engineering has become a widely adopted strategy to mitigate
these localized states.
Anion vacancies
The formation of anion vacancies directly leads to undercoordination of neighboring Pb ions, rendering
2+
them electron traps via dangling bonds. Notably, the extensive research on additive molecules targeting
undercoordinated Pb has necessitated a dedicated summary in this review, as the emergence of anion
2+