Organic solar cells with graded absorber layers processed from nanoparticle dispersions

Abstract

The fabrication of organic solar cells with advanced multi-layer architectures from solution is often limited by the choice of solvents since most organic semiconductors dissolve in the same aromatic agents. In this work, we investigate multi-pass deposition of organic semiconductors from eco-friendly ethanol dispersion. Once applied, the nanoparticles are insoluble in the deposition agent, allowing for the application of further nanoparticulate layers and hence for building poly(3-hexylthiophene-2,5-diyl):indene-C60 bisadduct absorber layers with vertically graded polymer and conversely graded fullerene concentration. Upon thermal annealing, we observe some degrees of polymer/fullerene interdiffusion by means of X-ray photoelectron spectroscopy and Kelvin probe force microscopy. Replacing the common bulk-heterojunction by such a graded photo-active layer yields an enhanced fill factor of the solar cell due to an improved charge carrier extraction, and consequently an overall power conversion efficiency beyond 4%. Wet processing of such advanced device architectures paves the way for a versatile, eco-friendly and industrially feasible future fabrication of organic solar cells with advanced multi-layer architectures.

Can Polymer Solar Cells Open the Path to Sustainable and Efficient Photovoltaic Windows Fabrication?

“…Multilayer P3HT: ICBA active layers produced through sequential deposition of NP from EtOH further improves the PCE to 4.2 % using a lower annealing temperature of 150 8C. [69] Using water as non-solvent for reprecipitation produced low PCEs below 0.2 % after annealing at 160 8C suggesting that EtOH might be a more adequate option when it comes to the fabrication of efficient PSCs from eco-friendly nanoparticle dispersions. [70] Although the above mentioned methods considerably reduce the amount of hazardous solvent employed, the necessary time to fabricate the devices is largely increased.…”

“…also produced devices with PCEs up to 3.5 % using EtOH a less harmful solvent. Multilayer P3HT : ICBA active layers produced through sequential deposition of NP from EtOH further improves the PCE to 4.2 % using a lower annealing temperature of 150 °C . Using water as non‐solvent for reprecipitation produced low PCEs below 0.2 % after annealing at 160 °C suggesting that EtOH might be a more adequate option when it comes to the fabrication of efficient PSCs from eco‐friendly nanoparticle dispersions …”

Water‐Processable Amphiphilic Low Band Gap Block Copolymer:Fullerene Blend Nanoparticles as Alternative Sustainable Approach for Organic Solar Cells

“…Additionally, compared to NPs prepared with the reprecipitation approach, [22,23] the highly stable BCP5 colloidal dispersions can be easily handled, stored for few months and deposited as thin films. In fact, unlike previous studies on water-based NP formation, by combining the conjugated block with a short hydrophilic P4VP tail, highly stable aqueous suspensions were obtained with no further purification process.…”

“…[19] An alternative route to bypass the limitations of surfactantstabilized NPs is the reprecipitation technique, in which the organic blend is first dissolved in an organic solvent and rapidly injected into alcoholic medium. [22,23] However, the absence of the stabilizer requires lowering the solid content to prevent the suspended NPs rapid aggregation into large particles. [20,21] NP-OPVs based on PAT-ICBA blend with performances (PCE up to 4.1%) slightly lower than those of the conventionally chlorinated solvent-processed devices (4-6%) can be produced with this approach which is partially attributed to optimized blend NP morphologies obtained after a thermal treatment at 150 °C.…”

Indium Tin Oxide–Based Fully Spray‐Coated Inverted Solar Cells with Nontoxic Solvents: The Role of Buffer Layer Interface on Low‐Bandgap Photoactive Layer Performance

“…A key feature of this work is the replacement of harmful solvents and the optimization of spray deposition process using green solvents. In particular, chlorinated solvents such as chlorobenzene (CB), o‐dichlorobenzene (DCB), and chloroform used in the preparation of the active layer are not sustainable from the environmental point of view (toxic to the environment and humans) and, therefore, are not suitable for the scalability of the processes on a large area . Hence, the replacement of the chlorinated solvents with nonchlorinated aromatics ones can pave the way to the large‐area fabrication of polymeric solar cells.…”