Degradation Mechanisms in Organic Photovoltaic Devices

Organic photovoltaic devices offer lightweight, flexible solar conversion but suffer from diverse degradation pathways that limit their operational lifetime. Intrinsic mechanisms include morphological evolution within the active layer—phase separation of donor and acceptor, crystallisation of small-molecule acceptors, polymer chain rearrangement and trap‐state formation under illumination. Chemical reactions driven by oxygen, moisture or ultraviolet photons lead to oxidation of electrodes, interlayers and conjugated polymers, causing increased series resistance, reduced charge generation and enhanced recombination. Thermal and mechanical stresses induce domain coarsening and loss of percolation pathways when temperatures approach the glass transition of organic constituents. Extrinsic factors such as water and oxygen ingress through imperfect encapsulation attack hygroscopic layers (notably PEDOT:PSS) and catalyse photo‐oxidation of active semiconductors. Electrode degradation via metal migration, delamination or deposition‐induced defects further compromises performance. These interconnected processes dictate device stability and have motivated advances in material design, interface engineering and encapsulation methods to mitigate each degradation route.

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Technical terms

Bulk heterojunction: A nanoscale interpenetrating network of donor and acceptor materials facilitating efficient charge separation and transport.

Glass transition temperature (Tg): The threshold temperature at which an amorphous organic material transitions from a rigid glassy state to a more mobile, rubbery state, influencing morphological stability.

Phase separation: The process by which blended donor and acceptor components segregate into distinct domains, affecting charge mobility and recombination dynamics.

π–π stacking: Non‐covalent interactions between aromatic rings that govern molecular packing, crystallinity and charge transport properties.

Encapsulation: The deposition of barrier layers to prevent ingress of oxygen and moisture into sensitive device regions, thereby protecting the organic semiconductors.

Non‐fullerene acceptor: A class of acceptor materials alternative to fullerene derivatives, offering tunable optoelectronic properties but exhibiting distinct crystallisation and stability behaviours.

References

1. Effect of Thermal Stress on Morphology in High-Performance Organic Photovoltaic Blends. JACS Au (2024).
2. Overcoming Moisture‐Induced Degradation in Organic Solar Cells. Advanced Engineering Materials (2023).
3. Aerosol‐Jet‐Printed Encapsulation of Organic Photovoltaics. Advanced Engineering Materials (2023).