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

Abstract

The preparation of water‐processable nanoparticles (NPs) of polymer semiconductors assembled using an amphiphilic rod‐coil block copolymer (BCP), and their application to active layer sustainable fabrication of organic photovoltaic devices are reported. The hydrophobic rod is a p‐type semiconductor, while the hydrophilic coil is a short chain of poly‐4‐vinylpyridine strongly interacting with [6,6]‐phenyl‐C61‐butyric acid methyl ester (PC61BM). Through miniemulsion technique stable water‐suspended blend NPs are obtained, avoiding nonconducting surfactant use. The amphiphilic BCP fulfills a dual function, as surfactant for stabilizing the blend NPs and as electron donor material in the active layer. After mild annealing of obtained films, blend NPs interconnect with each other forming compact and uniform layers with adequate morphology for efficient charge percolation to the electrodes. Space‐charge limited hole mobility of ≈5 × 10−3 cm2 V−1 s−1 in BCP‐only NP films annealed at 120 °C (corresponding to a tenfold increase in mobility as compared to the p‐type semiconductor films spin‐coated from chlorinated solvents) indicates strong p–p interactions in the self‐assembled NPs. Blend NPs were covered with thin PC61BM layer and used as active layers in photovoltaic devices displaying high photocurrents (11.5 mA cm−2) and average power conversion efficiency of 2.53% after annealing at 90 °C.

Control of Shell Morphology in p–n Heterostructured Water‐Processable Semiconductor Colloids: Toward Extremely Efficient Charge Separation

“…To clearly compare them with pure PC60, we additionally made P3HT:PC60 NP as a reference. As shown in SAXS profiles of Figure b, it is found that the aggregated PC60‐ or PC60–PC 61 BM micelles yield a large structure in all NPs, possibly indicating the formation of a shell surrounding the P3HT core particles . Furthermore, the higher scattering intensity showing larger number of particles appears in the P3HT:PC60–CF–PCBM NPs, which can be monitored in the DLS (Figure c).…”

“…The indistinguishable morphology finally leads to the cluster formation like small particles are gathered within the whole PC60‐PC 61 BM particle (Full synthesis for the particle formation is shown in Figure S9, Supporting Information), its effect can be confirmed in SAXS data (Figure d). In particularly, slightly shifted structure factor peaks at q = 0.0205 Å −1 to the small q value were observed (inset Figure d and Figure S10a, Supporting Information), implying that the size of aggregated PC60 micelles was larger depending on higher PC 61 BM concentration . Through the above data, the estimated PC60–PC 61 BM structures are schematically characterized in Figure e.…”

“…Furthermore, the core–shell NPs showed shell morphology‐dependent charge separation property, which suggest that the surrounding shell environments including the structure and electronic charge density play an important role in promoting the particle activity. Consequently, photovoltaic cell performances over 5% were achieved according to the excellent charge separation event, and to the best of our knowledge, which is the best outcome in the water‐borne NP‐based devices . From the results, we could find the importance of controlling shell formation in the p–n heterostructured particles and a possibility for further improved device performances.…”

Strongly Iridescent Hybrid Photonic Sensors Based on Self-Assembled Nanoparticles for Hazardous Solvent Detection

“…As demonstrated by the photographs in Figure 1 , surface plasma treatment of the PDMS substrate is an essential step for ensuring that PS nanoparticles can be deposited from aqueous dispersions onto these high surface energy elastomeric substrates. Surface plasma treatment is a well-known technique that is often applied to improving the wetting properties of aqueous solutions onto hydrophobic layers such as poly(3,4-ethylenedioxythiophene) polystyrene sulfonate or PDMS [ 16 , 35 , 36 ].…”

Water-Processed Organic Solar Cells with Open-Circuit Voltages Exceeding 1.3V

“…However, during their conventional active layers processing, an enormous amount of chlorinated solvent waste is generated, which is dangerous for the human health and the environment [5,9]. To mitigate the negative impact of OSC fabrication on the environment, several strategies have been investigated recently, which include the use of "greener" solvents such as limonene or nonhalogenated benzene derivatives [10][11][12][13], the synthesis of new organic semiconductors that are readily soluble in polar solvents [14], the introduction of water-based organic semiconductor inks [15][16][17], and the development of new coating processes to reduce wastes [18,19]. Although high power conversion efficiencies (PCEs ) well over 10% can be achieved with OSC active layers processed from the abovementioned nonhalogenated solvents, the safety data sheets of these solvents indicate that they remain relatively hazardous to the environment [10,11].…”