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Wang et al. Energy Mater. 2026, 6, 600064 Page 17 of 34

Table 2. Representative additive engineering strategies for enhanced stability in perovskite solar cells
PCE
Strategy Component Additive Long-term stability Encapsulation Refs.
(%)
85% after 350 h at RT
CsFAMAPbBrI PFPA 22.42 No [132]
and RH 45%
FASnI 3-AMBTh 14.53 94% after 1,000 h in N 2 No [133]
Functional group bonding
Formamidine
sulfinic acid 24.1 85% after 1,000 h in N 2 \ [142]
FAPbI 3 at 50-60 °C
(FSA)
Polymer/Crosslinker Cs 0.05 (FA 0.98 MA 0.02 ) 0.95 Pb(I 0.98 Br 0.02 ) 3 PY-IT 23.57 80% after 1,000 h in the Yes [134]
protection air
93.5% after 2,000 h in
CsFAMAPbSnI 4PBA 23.45 No [136]
N 2 at 25 °C
Hydrophobic barriers Stable performance after
MPEABr 24.4 850 h at 15-35 °C and Yes [139]
FAPbI 3
RH between 40%-90%
LTZ 24.9 80% after 1,968 h in N 2 No [140]
FAPbI 3
Suppression of ion at 60 °C
migration 85.9% after 1,032 h at 85
HL38 21.98 \ [141]
FA 0.9 Cs 0.1 PbBr 0.2 I 2.8
°C
PCE: Power conversion efficiency; PFPA: perfluorophenylacylamide; 3-AMBTh: 3-aminomethyl-benzothiophene.
Energy-level alignment tuning for optimized photovoltaic performance
Optimal device performance requires a precise thermodynamic match between the perovskite’s conduction
band minimum (CBM) and the lowest unoccupied molecular orbital (LUMO) of the ETL, as well as between
the perovskite’s valence band maximum (VBM) and the highest occupied molecular orbital (HOMO) of the
hole transport layer (HTL). Mismatched energy levels give rise to interfacial energy barriers, charge
accumulation, and severe non-radiative recombination, thereby limiting both photovoltaic performance and
long-term stability. As illustrated in Figure 4A, the energy-level configurations of recently reported
CsPbI Br (0 ≤ x ≤ 3) films and high-efficiency CTLs [143] are shown based on selected references [144-149] . To
3-x
x
achieve better energy-level alignment, it is important to select ETL and HTL materials matched to the
bandgap of the perovskite system and incorporate suitable additive molecules to modulate the VBM and
CBM of the perovskite.

Interfacial dipole engineering
A direct approach to modulate interfacial energy levels involves the introduction of molecular additives that
orient dipolar groups at perovskite interfaces while simultaneously passivating interfacial defects, thereby
achieving the dual benefits of energy-level tuning and defect mitigation through a single strategy. For
instance, Wang et al. [150] introduced chloropropyltrimethoxysilane (CPS) molecules, which feature a highly
electronegative chlorine atom at one terminus and a silane functional group at the other. The chlorine atoms
selectively coordinate with undercoordinated Pb at anion vacancy sites while the silane groups anchor to
2+
the perovskite surface to facilitate the formation of an ordered monolayer. This dipole layer generates a
microscopic electric field oriented from the perovskite toward the HTL, inducing a downward shift in the
surface vacuum level and effectively reducing the perovskite work function by 0.35 eV [Figure 4B].
Consequently, the energy barrier between the perovskite VBM and the HTL HOMO level is significantly
narrowed from 0.42 to 0.01 eV [Figure 4C]. Similarly, Sung et al. [151] employed
[2-(9H-carbazol-9-yl)ethyl]phosphonic acid (CEPA), whose phosphonic acid groups form strong
coordination interactions with undercoordinated Pb on the perovskite surface, passivating interfacial
2+
defects, while the dipole moment of the outward-oriented carbazole groups induces an upward shift in the
vacuum energy level, thereby achieving dual functionality of defect mitigation and interfacial energy-level