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Particle-Size Distribution and Surface Properties Enable Air-Stable Organic Photovoltaics via Self-Assembled Layers
Po-Yen Chang1, Ting-Ying Huang2, Le Phuoc Thien Duyen3
1Institute of Polymer Science and Engineering, National Taiwan University, Taipei 106319, Taiwan.
ACS Applied Materials & Interfaces
|March 16, 2026
Summary
A new carbazole-based material optimizes self-assembled layers for efficient and air-stable organic photovoltaics (OPVs). This strategy enhances surface properties, leading to high power conversion efficiencies and improved device durability.
Area of Science:
- Materials Science
- Organic Electronics
- Surface Chemistry
Background:
- Organic photovoltaics (OPVs) require optimized interfaces for high efficiency and stability.
- The NiOx/active-layer interface presents challenges due to roughness and energy level mismatch.
- Self-assembled monolayers (SAMs) are crucial for tuning interfacial properties.
Purpose of the Study:
- To develop a particle-size-distribution (PSD) and surface-property-guided strategy for optimizing buried interfaces in OPVs.
- To introduce a novel carbazole-based phosphonic acid, pPhPADCB, as an efficient hole-selective interfacial layer.
- To establish quantitative links between SAM assembly metrics and surface properties for designing durable OPVs.
Main Methods:
- Synthesis and characterization of pPhPADCB, a carbazole-based phosphonic acid.
- Particle-size-distribution (PSD) analysis to evaluate SAM uniformity and coverage on NiOx.
- Kelvin probe force microscopy (KPFM) to assess surface potential and work function modification.
- Fabrication and testing of organic photovoltaic devices using pPhPADCB as an interfacial layer.
Main Results:
- pPhPADCB forms a more uniform SAM with higher surface coverage on NiOx compared to controls.
- KPFM confirmed a favorable work-function shift and reduced potential fluctuations after pPhPADCB treatment.
- pPhPADCB-enabled OPVs achieved high power conversion efficiencies (PCEs) of 19.96% (PM6:L8-BO) and 19.65% (D18:L8-BO).
- Devices demonstrated excellent air stability, retaining over 80% of initial PCE after 1000 hours of ambient storage.
Conclusions:
- The phenyl spacer in pPhPADCB enhances molecular rigidity, ordering, and interfacial compatibility, leading to optimized contact formation.
- The study provides practical design rules for SAM interlayers by linking assembly metrics to surface properties.
- This strategy enables the development of highly efficient and environmentally durable organic photovoltaic devices.
