Stability Mechanisms in Organic Photovoltaic Systems

Organic photovoltaic systems harness the unique electronic properties of conjugated polymers and small‐molecule semiconductors blended with fullerene or non-fullerene acceptors to convert sunlight into electrical power. Despite rapid improvements in efficiency, operational stability remains the foremost barrier to commercial deployment. Degradation arises from morphological evolution of the bulk heterojunction, photochemical reactions leading to chemical by-products, light-induced phase separation (‘burn-in’), and interface deterioration under thermal or environmental stress. Key strategies to mitigate these losses include molecular design of donor and acceptor materials for enhanced miscibility, incorporation of antioxidant additives, interface engineering to inhibit migratory processes, and architectural modifications such as inverted device layouts or optical filtering. Together, these approaches seek to preserve the nanoscale morphology essential for efficient charge generation and transport, thereby extending device lifetimes under real-world operating conditions.

Research from Nature Portfolio

Recent studies have revealed that spontaneous spinodal demixing of donor and acceptor phases can trigger an abrupt burn-in decline in photocurrent. Detailed theoretical and experimental analyses have shown that even materials optimised for high performance may undergo phase separation at ambient conditions, reducing charge generation and accelerating early-stage degradation.

Investigations into device architecture have demonstrated that inverted organic solar cells employing zinc oxide substrates exhibit substantially enhanced thermal and environmental stability compared with conventional layouts. By suppressing nucleation and growth of fullerene domains at elevated temperatures, these inverted configurations maintain over 98 % of initial efficiency after prolonged ageing at 85 °C.

A more recent work has uncovered that common processing additives, notably 1,8-diiodooctane, can act as photoacids under ultraviolet irradiation, releasing acidic species that attack conjugated polymers. This mechanism accelerates degradation in benzodithiophene‐based systems, underscoring the need to reassess additive chemistry in pursuit of inherently more stable blends.

Stability Mechanisms in Organic Photovoltaic Systems publication trend

The graph below shows the total number of articles in stability mechanisms in organic photovoltaic systems across all publications each year (not limited to Nature Index journals).

Technical terms

Bulk heterojunction: Interpenetrating network of donor and acceptor materials forming the active layer for efficient exciton dissociation and charge transport.

Spinodal demixing: Spontaneous phase separation in a homogeneous blend driven by thermodynamic instability, leading to morphological coarsening.

Photodimerization: Light‐induced formation of covalent bonds between fullerene molecules, creating inactive aggregates that reduce photocurrent.

Photoacid: A compound that generates acidic species upon exposure to light, promoting polymer degradation and device failure.

Triplet quenching: Deactivation of long‐lived excited states to prevent formation of reactive oxygen species and oxidative damage.

References

1. All-Polymer Solar Cells and Photodetectors with Improved Stability Enabled by Terpolymers Containing Antioxidant Side Chains. Nano-Micro Letters (2023).
2. Abnormal strong burn-in degradation of highly efficient polymer solar cells caused by spinodal donor-acceptor demixing. Nature Communications (2017).
3. Toward Improved Lifetimes of Organic Solar Cells under Thermal Stress: Substrate-Dependent Morphological Stability of PCDTBT:PCBM Films and Devices. Scientific Reports (2015).
4. 1,8-diiodooctane acts as a photo-acid in organic solar cells. Scientific Reports (2019).
5. Morphological and electrical control of fullerene dimerization determines organic photovoltaic stability. Energy & Environmental Science (2016).
6. Suppressing photooxidation of conjugated polymers and their blends with fullerenes through nickel chelates. Energy & Environmental Science (2017).
7. Significant Stability Enhancement in High‐Efficiency Polymer:Fullerene Bulk Heterojunction Solar Cells by Blocking Ultraviolet Photons from Solar Light. Advanced Science (2015).