Chang, Y. C., Larrain, F. A., Fuentes-Hernandez, C., Park, Y., & Kippelen, B. (2023). Inverted organic tandem solar cells with a charge recombination stack employing spatially confined p-type electrical doping. J. Appl. Phys., 134(9), 095502.
Abstract: We report on the application of solution-based p-type electrical doping using 12-molybdophosphoric acid hydrate (PMA) to the fabrication of organic tandem solar cells. Such a doping approach leads to a spatially confined vertical doping profile down to a limited depth from the surface of polymer films, thus allowing the hole-collecting component of the charge recombination stack to be embedded in the photoactive layer of the bottom sub-cell. This simplifies the device architecture by removing the need for an extra dedicated hole-collecting layer. It is shown that this novel charge recombination stack comprising a PMA-doped bottom photoactive layer and a trilayer of Ag/AZO/PEIE is compatible with a solution-processed top photoactive layer. The fabricated inverted organic tandem solar cells exhibit an open-circuit voltage that is close to the sum of the open-circuit voltages of the individual sub-cells, and a fill factor that is close to the better fill factor of the two sub-cells.
|
Larrain, F. A., Fuentes-Hernandez, C., Chang, Y. C. H., Rodriguez-Toro, V. A., Abraham, S., & Kippelen, B. (2021). Increasing Volume in Conjugated Polymers to Facilitate Electrical Doping with Phosphomolybdic Acid. ACS Appl. Mater. Interfaces, 13(19), 23260–23267.
Abstract: Molecular p-type electrical dopants have been proven useful to fine-tune the optoelectronic properties of bulk organic semiconductors and their interfaces. Here, the volume in polymer films and its role in solution-based electrical p-type doping using phosphomolybdic acid (PMA) are studied. The polymer film volume was controlled using two approaches. One is based on heating both the PMA solution and the film prior to immersion. The second is based on coating the polymer film with a liquid blend that contains the PMA solution and a swelling solvent. 31P NMR and FTIR experiments indicate that the Keggin structure appears to be preserved throughout the doping process. Results show that increasing the polymer volume facilitates the infiltration of the PMA Keggin structure, which results in an increased electrical p-type doping level.
|
Nam, M., Park, Y., Lee, C., Kim, G., Larrain, F. A., Fuente-Hernandez, C., et al. (2023). Single-layer organic photovoltaics fabricated via solution-based electrical doping of ternary bulk heterojunction films. Chem. Eng. J., 466, 143340.
Abstract: The commercial viability of organic photovoltaics (OPVs) can be improved by simplifying their device geometry and easing fabrication complexity. Here, we demonstrate that solution-based p-type electrical doping of ternary bulk heterojunction (BHJ) films, which comprise 2 donor polymers and 1 fullerene acceptor (2D:1A), enables the realization of efficient single-layer OPVs. Systematic and detailed investigations of the optoelectronic charac-teristics of films with varying donor ratios, and their photovoltaic performance, demonstrate p-type electrical doping via post-process immersion into a 12-molybdophosphoric acid hydrate (PMA) solution, resulting in a reduced trap density and charge recombination without significantly changing the BHJ morphology. Further-more, PMA doping of films comprising optimized ternary blend compositions and polyethylenimine enables the demonstration of single-layer OPVs with economic top electrode metals and a high level of performance under outdoor and indoor illumination conditions. These PMA-doped 2D:1A BHJ films are an attractive platform to reduce the efficiency-cost gap and accelerate the commercialization of OPVs for emerging applications.
|
Park, Y., Fuentes-Hernandez, C., Kim, K., Chou, W. F., Larrain, F. A., Graham, S., et al. (2021). Skin-like low-noise elastomeric organic photodiodes. Sci. Adv., 7(51), eabj6565.
Abstract: Stretchable optoelectronics made of elastomeric semiconductors could enable the integration of intelligent systems with soft materials, such as those of the biological world. Organic semiconductors and photodiodes have been engineered to be elastomeric; however, for photodetector applications, it remains a challenge to identify an elastomeric bulk heterojunction (e-BHJ) photoactive layer that combines a low Young's modulus and a high strain at break that yields organic photodiodes with low electronic noise values and high photodetector performance. Here, a blend of an elastomer, a donor-like polymer, and an acceptor-like molecule yields a skin-like e-BHJ with a Young's modulus of a few megapascals, comparable to values of human tissues, and a high strain at break of 189%. Elastomeric organic photodiodes based on e-BHJ photoactive layers maintain low electronic noise current values in the tens of femtoamperes range and noise equivalent power values in the tens of picowatts range under at least 60% strain.
|
