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Wen et al. J. Mater. Inf. 2025, 5, 30 https://dx.doi.org/10.20517/jmi.2024.102 Page 9 of 21

number of atoms. However, the solvation free energy exhibits an inverse relationship with the number of
atoms, meaning that larger molecules tend to have lower solvation free energies, which enhances their
solubility in chlorobenzene solvent, as depicted in Figure 2C. Chlorobenzene was selected as the solvent for
solvation free energy calculations due to its widespread use in PSC fabrication, particularly for dissolving
SM-HTMs such as spiro-OMeTAD [57-60] . This choice ensures that the solvation free energy calculations align
with experimental conditions, providing a reliable basis for predicting HTM performance and facilitating
comparisons with spiro-OMeTAD. As a weakly polar solvent, chlorobenzene effectively dissolves non-polar
or weakly polar HTMs, preventing excessively strong solvent-molecule interactions. This ensures uniform
HTL film formation and minimizes over-solvation or interference with the crystallization of the perovskite
layer, ultimately improving the device’s optoelectronic efficiency and stability. The choice of solvent is
crucial in determining the solvation free energy and solubility of HTM molecules. Strong polar solvents
[such as N,N-dimethylformamide (DMF) or ethanol] may reduce solvation free energy and increase
solubility, but they can also leave solvent residues or damage the perovskite layer. Non-polar solvents (such
as toluene or n-hexane) may increase solvation free energy and decrease solubility. Chlorobenzene, as a
weakly polar solvent, strikes an optimal balance between solubility and film formation, making it suitable
for processing most HTMs. Figure 2D reveals that the maximum absorption peak increases with the
number of atoms, indicating a redshift in the absorption spectrum as molecular size grows. Additionally, as
illustrated in Figure 2E, the hydrophobicity (LogP value) is directly proportional to the number of atoms,
implying that larger molecules exhibit stronger hydrophobic characteristics. Finally, the SAScore of a
molecule also increases with the number of atoms, as shown in Figure 2F, indicating that larger molecules
are more challenging to synthesize.

[61]
In addition, performance data for seven previously reported HTMs, including spiro-OMeTAD , DTPC8-
D
w
a
ThDTPA , T P C 1 3 - ThTPA , T P - C6Th , YZ18 , YZ22 , n d T P A - T V T - TPA , e r e a l s o
D
[64]
[63]
[62]
[61]
[65]
[64]
calculated, with detailed values provided in Supplementary Table 1. It is important to note that the B3LYP
functional tends to underestimate the HOMO-LUMO gap and overestimate the HOMO level. As a result,
the calculated HOMO values are generally higher than experimental values, consistent with prior
literature [61-63,66,67] . This alignment validates the accuracy of our structural model and computational
methodology. It is noteworthy that this study is designed to address the critical limitations of spiro-
OMeTAD, including its low hole mobility, demanding synthesis requirements, and high production costs,
through the development of novel SM-HTMs. The performance data of spiro-OMeTAD were used as a
reference for screening high-throughput calculation results.
The screening process was primarily based on six criteria: HOMO level, hole reorganization energy,
solvation free energy, maximum absorption peak, LogP, and SAScore. First, 7,222 molecules were pre-
screened based on the HOMO energy level and maximum absorption peak. These two parameters are
critical for identifying candidate materials capable of effectively replacing spiro-OMeTAD in photovoltaic
devices. Specifically, the HOMO energy level ensures proper energy alignment between the HTL and the
perovskite absorber, which is essential for efficient charge extraction. Simultaneously, the absorption
maximum mitigates spectral overlap with the perovskite layer, thereby minimizing parasitic light absorption
by the HTL and maximizing light utilization by the perovskite active layer. These combined properties
guarantee that the newly designed SM-HTMs can be seamlessly integrated into device architectures
analogous to those employing spiro-OMeTAD. The calculated HOMO value of spiro-OMeTAD ± 0.1 eV
(i.e., -4.117 to -4.317 eV) was used as the criterion for HOMO screening. Furthermore, referencing spiro-
OMeTAD, we also set a screening criterion for the maximum absorption peak. To prevent excessive light
absorption by the HTL, which could compromise device efficiency, the maximum absorption peak of the
7,222 molecules was required to be less than 400 nm, ensuring optimal photoelectric conversion efficiency.