Spray Coating Techniques for Organic Photovoltaic Devices

Spray coating has emerged as a low-cost, scalable route to deposit thin films for organic photovoltaic (OPV) devices under ambient conditions. By atomising a solution containing conjugated polymers and fullerene or non-fullerene acceptors into micrometre-sized droplets, a continuous active layer is formed upon solvent evaporation. Techniques range from airbrush and ultrasonic nozzles to electrospray and spray pyrolysis, each offering specific control over droplet size, spray rate, and substrate temperature. Compared with conventional spin coating or vacuum evaporation, spray coating enables roll-to-roll processing of large-area modules, reduces material wastage, and allows multilayer architecture through sequential deposition using orthogonal solvents. Key challenges include optimisation of film uniformity, surface roughness, solvent drying dynamics and donor–acceptor phase separation within the bulk heterojunction. Recent advances in in situ diagnostics, such as grazing-incidence scattering, have elucidated the hierarchical nanostructure of sprayed films, guiding the tuning of spray parameters to achieve high charge-carrier mobility and improved light absorption. These developments underpin the growing interest in upscaling OPV production for portable electronics, building-integrated photovoltaics and energy-harvesting textiles, offering a pathway to sustainable, flexible solar energy solutions.

Research from Nature Portfolio

Recent studies have applied advanced scattering techniques to map the hierarchical morphology of spray-deposited polymer:fullerene blend films. Investigations reveal that droplet boundaries guide the formation of interconnected networks of crystalline polymer domains and nanoparticle clusters, enhancing transverse electron and hole transport. Comparative analysis with spin-coated counterparts shows that tailored post-treatments, including thermal and solvent vapour annealing, can refine phase separation and improve power conversion efficiencies in centimetre-scale devices. These insights establish a clear relationship between spray process control, bulk heterojunction structure and device performance, paving the way for reliable large-area OPV module fabrication.

Spray Coating Techniques for Organic Photovoltaic Devices publication trend

The graph below shows the total number of articles in spray coating techniques for organic photovoltaic devices across all publications each year (not limited to Nature Index journals).

Technical terms

Bulk heterojunction (BHJ): A blend of donor and acceptor materials forming an interpenetrating network for efficient exciton dissociation and charge transport.

Ultrasonic spray coating: A method using high-frequency vibrations to generate fine droplets, enabling uniform thin films with controlled thickness.

Roll-to-roll processing: A continuous fabrication technique for large-area devices, in which substrates move through coating, drying and annealing stations.

Electrospray: A technique where an electric field is applied to create charged droplets, facilitating precise control over deposition and film morphology.

References

1. Spray-on Thin Film PV Solar Cells: Advances, Potentials and Challenges. Coatings (2014).
2. Fundamental Study on the Effect of Spray Parameters on Characteristics of P3HT:PCBM Active Layers Made by Spray Coating. Coatings (2015).
3. Polymer-based solar cells having an active area of 1.6 cm2 fabricated via spray coating. APL Materials (2015).
4. Correlation between Hierarchical Structure and Processing Control of Large-area Spray-coated Polymer Solar Cells toward High Performance. Scientific Reports (2016).
5. Substrate Temperature Effect on Charge Transport Performance of ZnO Electron Transport Layer Prepared by a Facile Ultrasonic Spray Pyrolysis in Polymer Solar Cells. International Journal of Photoenergy (2015).
6. Large-area bi-component processing of organic semiconductors by spray deposition and spin coating with orthogonal solvents. Applied Physics A (2009).
7. Electrosprayed Molybdenum Trioxide Aqueous Solution and Its Application in Organic Photovoltaic Cells. PLOS ONE (2014).