From Molecular Design to Morphology Control: How Small-Molecule Donors Improve the Efficiency, Stability, and Processability of Organic Solar Cells

Introduction

Organic solar cells (OSCs) are lightweight, flexible, semitransparent, and compatible with solution processing, making them promising for flexible photovoltaics, building-integrated photovoltaics, indoor photovoltaics, and printable photovoltaic devices. Their core functional layer is typically composed of an electron donor and an electron acceptor, which together form a bulk heterojunction (BHJ) structure to enable light absorption, exciton dissociation, charge transport, and charge collection.

In organic solar cells, small-molecule donors were long regarded as a supplementary route alongside polymer donors. With the development of non-fullerene acceptors (NFAs), all-small-molecule organic solar cells (all-SMOSCs), and non-halogenated solvent processing, the value of small-molecule donors is no longer limited to “providing hole-transport pathways.” More importantly, through well-defined molecular structures, tunable side chains and end groups, and designable intermolecular interactions, small-molecule donors can influence the entire process from solution pre-aggregation to thin-film phase separation, ultimately determining the power conversion efficiency (PCE), stability, and processing adaptability of the device.

1. Material Characteristics and Research Value of Small-Molecule Donors

The key advantage of small-molecule donors lies in their “structural certainty.” Compared with polymer donors, small-molecule materials usually have well-defined molecular structures, precise molecular weights, relatively easier purification processes, and better batch-to-batch reproducibility. These features are beneficial for establishing clear structure–property relationships, as well as for material screening and reproducible device results.

However, small-molecule donors also have inherent challenges. Because of their relatively low molecular weight and strong crystallization tendency, some small molecules are prone to excessive aggregation during film formation, resulting in rough films, overly large phase-separation domains, or insufficient continuous transport pathways. Therefore, the design of high-performance small-molecule donors cannot focus only on absorption spectra and energy levels; it must also consider solubility, crystallization rate, molecular orientation, donor/acceptor miscibility, and thin-film morphology stability.

Dimension	Advantages of Small-Molecule Donors	Issues That Need to Be Controlled
Molecular structure	Well-defined structure, facilitating structure–property relationship studies	Minor structural changes may cause significant morphology variations
Purification and reproducibility	Easier purification and relatively smaller batch-to-batch differences	High purity still needs to be combined with a stable film-forming process
Molecular packing	Easy formation of ordered π–π stacking	Excessively strong crystallization may lead to coarse domains
Solution processing	Solubility can be adjusted through side-chain engineering	Uncontrolled solution aggregation and non-uniform film formation must be avoided
Application potential	Suitable for all-small-molecule systems and reproducible studies	Non-halogenated solvent processing, thick-film tolerance, and large-area processing adaptability still need improvement

2. An Excellent Small-Molecule Donor Needs to Perform Three Key Functions

A small-molecule donor is not merely an “electron donor.” In high-efficiency organic solar cells, it should perform at least three types of functions.

2.1 Light-Absorption Function

The donor needs to provide effective absorption within the solar spectrum and form complementary absorption with the acceptor. In early fullerene-based systems, the donor usually played the main role in light absorption. In modern non-fullerene acceptor systems, however, the acceptor often exhibits strong near-infrared absorption. Therefore, donor absorption does not necessarily need to be increasingly red-shifted; instead, it should complement the acceptor absorption in a reasonable manner to reduce gaps in spectral response.

2.2 Energy-Level Matching Function

The highest occupied molecular orbital (HOMO) of the donor affects the open-circuit voltage and energy loss, while the lowest unoccupied molecular orbital (LUMO) is related to exciton dissociation and charge-transfer processes. The HOMO energy level should be evaluated comprehensively based on the acceptor energy levels, charge-transfer states, non-radiative recombination losses, and device architecture.

2.3 Morphology-Regulation Function

Small-molecule donors also influence phase separation, crystallinity, molecular orientation, and continuous transport pathways in the active layer. Many differences in device performance do not arise from absorption or energy levels themselves, but from the arrangement of donors and acceptors in the thin film. This is particularly important for all-small-molecule systems, because both the donor and acceptor may have strong crystallization tendencies, which can easily lead to oversized domains, insufficient interfacial area, or unfavorable vertical distribution.

3. Molecular Backbone: Determining Absorption, Energy Levels, and Planarity

The backbone design of a small-molecule donor first determines its electronic structure. Common strategies include donor–acceptor-type conjugated backbones, extended π-conjugation length, introduction of electron-withdrawing units, modulation of end-group electronic effects, and construction of intramolecular non-covalent interactions.

3.1 The Conjugated Backbone Affects the Absorption Range

Extending π-conjugation is generally beneficial for enhancing intramolecular charge transfer, reducing the optical bandgap, and shifting absorption toward longer wavelengths. However, excessive extension of the conjugated system may reduce solubility, strengthen crystallization too much, or narrow the film-forming window. Therefore, backbone design requires a balance between light-absorption capability and processing performance.

3.2 Planarity Affects Charge Transport

Good molecular planarity helps enhance π–π stacking, improve hole mobility, and promote the formation of continuous transport pathways. However, stronger planarity is not always better. Excessively strong intermolecular packing may lead to large-scale crystallization, reduce the donor/acceptor interfacial area, and weaken exciton dissociation. Therefore, what high-performance small-molecule donors require is “controlled ordering,” rather than simply pursuing the strongest possible packing.

3.3 Non-Covalent Interactions Can Serve as Conformational Locks

Halogen bonding and weak intramolecular or intermolecular interactions between sulfur and oxygen, chlorine and sulfur, and fluorine and hydrogen can serve as non-covalent conformational locks. These interactions help restrict conformational twisting, enhance backbone planarity, and regulate molecular aggregation behavior. The BM-ClEH small-molecule donor reported in 2024 introduced an intramolecular non-covalent interaction between chlorine and sulfur, which improved molecular backbone rigidity and strengthened aggregation capability. Under non-halogenated solvent processing conditions using tetrahydrofuran (THF), this molecule helped improve solution pre-aggregation and the microstructure of the resulting film, enabling BM-ClEH:BO-4Cl all-small-molecule devices to achieve high efficiency.

4. Side Chains and End Groups: Determining Solubility, Crystallinity, and Miscibility

If the main-chain backbone determines the electronic structure of a material, then the side chains and end groups determine whether the material can form an appropriate thin film. Many small-molecule donors appear to have ideal absorption and energy levels in solution, but show poor performance after being fabricated into devices. The reason often lies in morphology issues caused by the side chains and end groups.

4.1 Side Chains Regulate Solubility and Crystallization Rate

The length of alkyl chains, branching position, degree of branching, and steric hindrance all influence material solubility. Longer or branched side chains generally help improve solubility, but may also weaken π–π stacking. Shorter or linear side chains favor tighter molecular packing, but may lead to insufficient solubility or overly strong crystallization.

Side-Chain Modification	Possible Positive Effects	Possible Risks
Increasing side-chain length	Improves solubility and film formation	Reduces molecular packing density
Introducing branched side chains	Suppresses excessive crystallization and broadens the processing window	May reduce mobility
Moving the branching point away from the main chain	Maintains a certain degree of π–π stacking	Limited improvement in solubility
Placing the branching point close to the main chain	Increases steric hindrance and improves solubility	May disrupt ordered molecular arrangement
Using aromatic side chains	Enhances specific intermolecular interactions	May induce complex aggregation behavior

4.2 End Groups Regulate Energy Levels and Self-Assembly

End groups not only affect HOMO/LUMO energy levels, but also change molecular dipole moments, crystallization modes, and donor/acceptor compatibility. Electron-withdrawing end groups can lower energy levels and enhance intramolecular charge transfer. Sulfur-containing, nitrogen-containing, or halogen-substituted end groups may regulate packing modes through non-covalent interactions.

End-group design needs to avoid two extremes: one is insufficient electron-withdrawing ability, which leads to unsatisfactory light absorption and energy-level matching; the other is overly strong crystallization induced by the end group, resulting in the formation of coarse crystalline domains in the film.

4.3 Miscibility Determines the Phase-Separation Scale

A small-molecule donor must form an appropriate degree of miscibility with the acceptor. Excessively strong miscibility can lead to insufficient phase separation and discontinuous charge-transport pathways. Excessively weak miscibility can lead to overly large domains and reduced exciton-dissociation efficiency. This issue is particularly important in all-small-molecule systems, because both small-molecule donors and small-molecule acceptors may crystallize rapidly, making the film-formation process more difficult to control.

5. From Solution Pre-Aggregation to Thin-Film Morphology: Performance Differences Often Begin in Solution

The morphology of the active layer is not formed only after complete solvent evaporation. Molecular aggregation states in solution, solvent–solute interactions, and the drying process jointly affect the final phase separation, crystallinity, and molecular orientation in the thin film.

5.1 Pre-Aggregation Affects the Film-Formation Pathway

In solution, if small-molecule donors exist completely as isolated molecules, the film may lack nucleation points for ordered packing during film formation. If pre-aggregation is too strong, large crystals may form rapidly during drying. The ideal state is to form moderate, controllable, and reproducible pre-aggregation, allowing the film to develop continuous transport pathways during drying without excessive coarsening.

The BM-ClEH:BO-4Cl all-small-molecule system reported in 2024 showed that the strongly aggregating small-molecule donor BM-ClEH could improve pre-aggregation in THF, thereby improving π–π stacking, phase separation, and exciton dissociation. The corresponding devices achieved a binary efficiency of 15.0% and a ternary efficiency of 16.1% under thermal annealing conditions. In contrast, the weakly aggregating control molecule BM-HEH, which lacks Cl···S non-covalent interactions, performed worse under the same processing conditions because of insufficient pre-aggregation, disordered π–π stacking, indistinct phase separation, and limited exciton dissociation.

5.2 Thin-Film Morphology Needs to Meet Three Requirements Simultaneously

A high-efficiency active layer generally needs to meet the following conditions:

Morphological Requirement	Corresponding Function	Consequence When Uncontrolled
Appropriate phase-separation scale	Ensures that excitons reach the donor/acceptor interface and dissociate	Oversized domains reduce short-circuit current
Continuous transport pathways	Promote the transport of holes and electrons to their respective electrodes	Discontinuous pathways reduce fill factor
Proper molecular orientation	Improves charge collection in the vertical direction	Poor orientation reduces mobility and current

The phase-separation scale is not simply “the smaller, the better.” Domains that are too small may lead to excessive donor/acceptor mixing and hinder carrier transport, while domains that are too large may cause excitons to recombine before reaching the interface. An ideal morphology should balance exciton dissociation and charge transport.

6. Application Adaptability of Small-Molecule Donors: Non-Halogenated Solvents, Thick-Film Processing, and Stability

Achieving a high PCE in the laboratory does not necessarily mean that a material has practical application potential. A truly valuable small-molecule donor needs to maintain performance under conditions closer to real manufacturing, including non-halogenated solvent processing, thicker active layers, large-area coating, and long-term stability.

6.1 Non-Halogenated Solvent Processing

Many high-efficiency organic solar cells rely on halogenated solvents such as chloroform, chlorobenzene, and o-dichlorobenzene. These solvents are beneficial for material dissolution and morphology regulation, but are unfavorable for environmentally friendly fabrication and scalable production. Therefore, processing with non-halogenated solvents such as toluene, xylene, and THF has become an important direction.

The difficulty of non-halogenated solvent processing lies in the fact that material solubility, drying rate, degree of pre-aggregation, and crystallization kinetics all change. For all-small-molecule systems, this problem is even more pronounced because the molecules have stronger crystallization tendencies.

6.2 Thick-Film Tolerance

Large-area printing and coating generally require the active layer to have high thickness tolerance. If a device can only achieve high efficiency in a very thin active layer, performance is likely to decrease during scale-up because of thickness fluctuations.

As a representative advance in morphology control for thick-film organic solar cells, Chen et al. reported in 2025 that introducing the organic semiconductor regulator AT-β2O into a blend system composed of the polymer donor D18-Cl and the small-molecule acceptor N3 could regulate the crystallization sequence of the active-layer components. This enabled single-junction devices to achieve a certified efficiency of over 20%, maintain good adaptability over an active-layer thickness range of 100–400 nm, and achieve a certified large-area module efficiency of 18.04%. This case mainly demonstrates the importance of crystallization kinetics and thick-film morphology control for scaling up organic solar cells; it does not mean that all small-molecule donor systems or all-small-molecule systems have reached this level.

6.3 Stability

The stability of small-molecule donor systems depends on multiple factors, including molecular chemical stability, thin-film morphology stability, donor/acceptor compatibility, interfacial-layer stability, and encapsulation conditions. Although all-small-molecule systems have advantages in terms of well-defined structures and batch-to-batch reproducibility, they may also suffer performance degradation because of small-molecule diffusion, crystalline rearrangement, or phase-separation evolution.

A 2025 study on the “donor alloy” strategy showed that introducing the structurally compatible small-molecule donor SD86 into the MPhS-C2:BTP-eC9 host system could form an MPhS-C2:SD86 donor alloy, optimizing the microstructure and carrier dynamics of the all-small-molecule active layer. This ternary all-SMOSC achieved a PCE of 18.51%, with a certified value of 18.40%, and exhibited good operational stability and thickness insensitivity. These results indicate that morphology stability has become a core criterion in small-molecule donor design.

7. Experimental Diagnosis: When Efficiency Is Low, Identify the Source of the Problem First

When the performance of a small-molecule donor device is unsatisfactory, it is not advisable to replace the material immediately. An effective approach is to break the problem down into absorption, energy levels, morphology, transport, and stability, and then conduct step-by-step analysis using appropriate characterization methods.

Experimental Observation	Possible Causes	Recommended Characterization Methods
Low short-circuit current density	Insufficient absorption, poor exciton dissociation, oversized domains, unfavorable vertical distribution	Ultraviolet-visible absorption spectroscopy (UV-vis), external quantum efficiency (EQE), photoluminescence (PL) quenching, atomic force microscopy (AFM), transmission electron microscopy (TEM)
Low open-circuit voltage	HOMO energy level too high, large energy loss, strong interfacial recombination	Cyclic voltammetry (CV), electroluminescence (EL), dark J–V, temperature-dependent J–V
Low fill factor	Imbalanced carrier mobility, discontinuous transport pathways, severe bimolecular recombination	Space-charge-limited current (SCLC), light-intensity-dependent J–V, grazing-incidence wide-angle X-ray scattering (GIWAXS)
Poor reproducibility	Unstable solution pre-aggregation, insufficient material purity, narrow film-forming window	Solution UV-vis, dynamic light scattering (DLS), high-performance liquid chromatography (HPLC), repeated film-formation tests
Performance decline in thick films	Poor vertical phase distribution, increased transport distance, enhanced recombination	Thickness-dependent J–V, SCLC, GIWAXS, time-of-flight secondary ion mass spectrometry (TOF-SIMS)
Poor thermal stability	Small-molecule migration, phase-separation coarsening, crystalline rearrangement	Thermal annealing aging tests, in situ GIWAXS, AFM, differential scanning calorimetry (DSC)

8. A Decision Framework for Small-Molecule Donor Design

Whether a small-molecule donor is worth further in-depth study can be evaluated using the following five questions.

8.1 Does It Provide Complementary Absorption?

The donor does not need to cover the entire solar spectrum, but it should form effective complementary absorption with the acceptor. If the acceptor already has strong near-infrared absorption, the donor can focus on supplementing absorption in the visible region and avoid open-circuit voltage losses caused by an excessively narrow bandgap.

8.2 Do the Energy Levels Support Low-Loss Charge Separation?

The HOMO and LUMO energy levels should match those of the acceptor while also taking into account open-circuit voltage, exciton dissociation, and non-radiative recombination. A “deeper HOMO” or “narrower bandgap” should not be used as the sole evaluation criterion.

8.3 Is Molecular Packing Controllable?

An ideal small-molecule donor should have sufficient π–π stacking to support hole transport, but should not form excessively coarse crystalline domains. Molecular planarity, non-covalent interactions, end groups, and side chains need to be regulated together.

8.4 Does It Have a Stable Film-Forming Window?

The material should have suitable solubility and pre-aggregation behavior in the target solvent, and should be able to form a relatively stable thin-film morphology under different concentrations, drying rates, and annealing conditions.

8.5 Is It Suitable for Application-Oriented Processing Conditions?

Promising systems should gradually move from small-area devices, halogenated solvents, and thin-film spin coating toward non-halogenated solvents, thicker active layers, blade coating, slot-die coating, and other conditions that are closer to practical production.

9. Classification and Application Tables of Materials and Reagents Related to Small-Molecule Donor Organic Solar Cell Research

Table 1. Active-Layer Donor and Acceptor Materials

Category	CAS No.	Aladdin Cat. No.	Name	Specification or Purity	Product Features and Applications
Small-molecule donor	2410661-17-3	B1504660	BTR-Cl	——	Chlorinated small-molecule donor material, used to study end-group chlorination, molecular packing, phase-separation scale, and morphology regulation in all-small-molecule active layers.
Polymer donor	104934-50-1	P431318	Poly(3-hexylthiophene-2,5-diyl) (P3HT)	Regioregular, average Mw 85,000–100,000	Classic polymer donor material, used to construct donor/acceptor blend models and study crystallinity, phase separation, thermal annealing, and morphology evolution.
Polymer donor	1802013-83-7	P486798	PBDB-T-2F	Mn > 30,000	Medium-bandgap polymer donor material, used in non-fullerene acceptor systems to study complementary absorption, energy-level matching, and thin-film morphology optimization.
Polymer donor	1415929-80-4	P486690	PBDB-T	——	Benzodithiophene-based polymer donor material, used to study donor/acceptor compatibility, active-layer crystallization behavior, and device-performance comparisons.
Fullerene material	99685-96-8	F434635	Fullerene C₆₀	Sublimed grade, ≥99.9%	Basic fullerene material, used for fullerene acceptor derivatives, electron-transport behavior, and control systems in organic photovoltaics.
Fullerene material	115383-22-7	F757064	Fullerene C70	≥99.5%	C70 fullerene material, used for the development of fullerene acceptor derivatives and the study of acceptor absorption characteristics.
Fullerene acceptor	160848-22-6	P400139	[6,6]-Phenyl-C61-butyric acid methyl ester	≥99.5%	Classic fullerene acceptor material, used in small-molecule donor and polymer donor devices to study phase separation, electron transport, and benchmark performance.
Fullerene acceptor	609771-63-3	P135215	[6,6]-Phenyl-C71-butyric acid methyl ester	≥97%, contains BHT stabilizer, mixture of isomers	C71 fullerene acceptor material, used to broaden visible-light absorption, optimize donor/acceptor blend morphology, and improve device current output.
Non-fullerene acceptor	1664293-06-4	I432187	ITIC	≥98%	Fused-ring non-fullerene acceptor material, used to study energy-level matching, crystallization behavior, and donor/acceptor compatibility in non-fullerene systems.
Non-fullerene acceptor	2304444-49-1	Y486933	Y6	≥98%	High-performance non-fullerene acceptor material, used to study near-infrared absorption, low energy loss, molecular packing, and active-layer morphology control.
Non-fullerene acceptor	2598965-39-8	B1504685	BTP-eC9		High-performance Y-series non-fullerene acceptor material, used to study donor/acceptor energy-level matching, phase-separation regulation, thick active layers, carrier transport, and all-small-molecule donor-alloy systems.
Non-fullerene acceptor	2668341-40-8	L1504695	L8-BO	——	Fused-ring non-fullerene acceptor material, used in high-efficiency blend systems to study crystallization kinetics, film-thickness adaptability, and morphology stability.
Non-fullerene acceptor	2447642-41-1	Y1504703	Y6-BO-4Cl	——	Chlorinated Y-series non-fullerene acceptor material, used in all-small-molecule systems for non-halogenated solvent processing, pre-aggregation regulation, and thin-film phase-separation studies.

Table 2. Active-Layer Film-Forming Solvents and Solution-Processing Solvents

Category	CAS No.	Aladdin Cat. No.	Name	Specification or Purity	Product Features and Applications
Halogenated film-forming solvent	108-90-7	C431386	Chlorobenzene	Anhydrous grade, ≥99.8%	Common film-forming solvent for organic photovoltaic active layers, used for donor/acceptor solubility screening and thin-film morphology regulation.
Halogenated film-forming solvent	95-50-1	D119675	o-Dichlorobenzene	Anhydrous grade, ≥99%	High-boiling halogenated film-forming solvent, used for dissolving poorly soluble conjugated materials, regulating drying rate, and controlling crystallization processes.
Halogenated film-forming solvent	67-66-3	C1522417	Chloroform (controlled precursor chemical)	USP, electronic grade, ≥99.5%	Common solvent for small-molecule donors and non-fullerene acceptors, used for spin-coating film formation, solution aggregation-state studies, and benchmark device conditions.
Non-halogenated film-forming solvent	108-88-3	T399633	Toluene (controlled precursor chemical)	Anhydrous grade, ≥99.8%	Non-halogenated aromatic solvent, used for greener active-layer processing, solubility evaluation, and screening of coating-process conditions.
Non-halogenated film-forming solvent	95-47-6	X1521078	o-Xylene	Extra-dry grade, ≥99%, water ≤30 ppm	Non-halogenated, high-boiling aromatic solvent, used for blade coating, slot-die coating, thick active layers, and drying-process control.
Non-halogenated film-forming solvent	1330-20-7	X1522441	Xylene	USP, electronic grade, ≥99.5%	Non-halogenated mixed aromatic solvent, used for active-layer solution formulation development, film-forming window screening, and scaled-up coating studies.
Non-halogenated film-forming solvent	109-99-9	T103263	Tetrahydrofuran (THF)	AR, ≥99%, contains 250 ppm BHT stabilizer	Non-halogenated ether solvent, used for pre-aggregation regulation in all-small-molecule systems, solution-state studies, and non-halogenated solvent processing exploration.

Table 3. Morphology-Regulating Additives and Molecular Building Blocks

Category	CAS No.	Aladdin Cat. No.	Name	Specification or Purity	Product Features and Applications
Morphology-regulating additive	98-95-3	N116217	Nitrobenzene	Excellent grade reagent, ≥99%	High-boiling aromatic additive, used to regulate the active-layer drying process, molecular aggregation, and donor/acceptor phase-separation behavior.
Morphology-regulating additive	101-84-8	D130016	Diphenyl ether	≥99.9% (GC)	High-boiling additive, used to regulate crystallization processes, phase-separation scale, and film uniformity in non-fullerene systems.
Morphology-regulating additive	1191-62-4	O109630	1,8-Octanedithiol	≥98%	Thiol additive, used to regulate molecular rearrangement, phase separation, and charge-transport pathways in fullerene systems and blend films.
Morphology-regulating additive	605-02-7	P160381	1-Phenylnaphthalene	≥97% (GC)	Aromatic additive, used to regulate acceptor aggregation, thin-film crystallization behavior, and thick active-layer morphology.
Morphology-regulating additive	24772-63-2	D473785	1,8-Diiodooctane	≥96%	Classic high-boiling additive, used to regulate donor/acceptor phase separation, crystallinity, and carrier-transport pathways.
Morphology-regulating additive	90-13-1	C104850	1-Chloronaphthalene	≥96%	High-boiling aromatic additive, used to slow film drying, regulate molecular packing, and improve active-layer microstructure.
End-group building block	141-84-4	R104132	Rhodanine	AR	Building block related to small-molecule donor end groups, used to construct electron-withdrawing end groups and regulate intramolecular charge transfer and molecular packing modes.

Note: The applicability of morphology-regulating additives is highly dependent on the material system and device architecture. Some high-boiling additives have relatively high toxicity, residue risks, or environmental compliance concerns. For scaled-up fabrication, safety, residue control, and alternative additive or solvent strategies should be comprehensively evaluated.

Table 4. Interfacial Layers, Transport Layers, and Electrode-Modification Materials

Category	CAS No.	Aladdin Cat. No.	Name	Specification or Purity	Product Features and Applications
Hole transport layer	1313-27-5	M431811	Molybdenum(VI) oxide	Suitable for analysis, premium grade	High-work-function metal oxide material, used for anode interface modification, hole-selective transport, and suppression of interfacial recombination.
Hole transport layer	155090-83-8	P191136	Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS)	PEDOT:PSS = 1:6, 1.5% in water	Water-dispersed hole-transport material, used for anode modification, hole collection, and construction of standard conventional devices.
Electron transport layer	4733-39-5	B293611	Bathocuproine (BCP)	Sublimed grade, ≥99.8% metals basis	Small-molecule electron-transport and exciton-blocking material, used for cathode interface modification, electron extraction, and interfacial energy-level regulation.
Electron transport layer	1314-13-2	Z592372	Nano zinc oxide dispersion	Particle size 30–45 nm, 36 wt.% in 1,2-propylene glycol monomethyl ether acetate solution	Nanostructured metal oxide dispersion, used as an electron transport layer in inverted devices, for cathode interface modification, and for low-temperature film-forming processes.
Cathode interfacial layer	1558023-86-1	A587416	PDINO	≥99%	Perylene diimide-based cathode interfacial material, used for electron extraction, interfacial dipole regulation, and inverted device structures.
Cathode interfacial layer	1020180-01-1	P1504721	PDINN	——	Perylene diimide-based cathode interfacial material, used for electron-selective contacts and interfacial charge collection in non-fullerene devices.
Cathode interfacial layer	889672-99-5	P487337	PFN-Br	——	Conjugated polyelectrolyte interfacial material, used to regulate cathode work function, promote electron extraction, and improve interfacial contact.
Cathode interfacial layer	2169941-79-9	P1504773	PNDIT-F3N-Br	——	Polymeric cathode interfacial material, used for electron transport, interfacial energy-level regulation, and construction of high-efficiency organic solar cells.
Self-assembled monolayer material	2377770-18-6	M404348	MeO-2PACz	≥98%	Carbazole phosphonic acid self-assembled monolayer material, used for transparent conductive oxide surface modification, hole-selective contact formation, and interfacial energy-level regulation.
Self-assembled monolayer material	20999-38-6	P405551	[2-(9H-Carbazol-9-yl)ethyl]phosphonic acid (2PACz)	≥98%	Carbazole phosphonic acid self-assembled monolayer material, used for anode interface modification, hole collection, and construction of low-loss interfaces.

Note: The above are representative Aladdin products. More product specifications can be searched on the Aladdin website using the product name, CAS number, or catalog number.

References

[1] Payne A.-J., Welch G. C. Development of Small Molecule Donors for Solution-Processed Organic Solar Cells. MilliporeSigma Technical Article.

[2] Gao W., Ma R., Dela Peña T. A., et al. Efficient all-small-molecule organic solar cells processed with non-halogen solvent. Nature Communications, 2024, 15, 1946.

[3] Yi J., Zhang G., Yu H., Yan H. Advantages, challenges and molecular design of different material types used in organic solar cells. Nature Reviews Materials, 2024, 9, 46–62.

[4] Gao Y., Xu L.-Y., Chen X., Xiao B., Gao W., Xia J., Sun R., Min J. Highly efficient all-small-molecule organic solar cells with excellent operational stability and blend-thickness tolerance. Energy & Environmental Science, 2025, 18, 7302–7312. DOI: 10.1039/D5EE01162K.

[5] Kong M., Lee J., Song S., et al. Progress and Future Potential of All-Small-Molecule Organic Solar Cells Based on the Benzodithiophene Donor Material. Molecules, 2023, 28, 3171.

[6] Yang X., Gao Y., Xu L.-Y., et al. Efficient and stable all-small-molecule solar cells enabled by incorporating a designed giant molecule acceptor. Energy & Environmental Science, 2024. DOI: 10.1039/D4EE01705F.

[7] Chen H., Huang Y., Zhang R., et al. Organic solar cells with 20.82% efficiency and high tolerance of active layer thickness through crystallization sequence manipulation. Nature Materials, 2025, 24, 444–453.

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