Improved Electron Selectivity in Silicon Solar Cells by Cathode Modification with a Dipolar Conjugated Polyelectrolyte Interlayer

• Published in: ACS applied energy materials Vol. 2; no. 8; pp. 5954 - 5959
• Main Authors: Ros, Eloi, Barquera, Zaira, Ortega, Pablo R, Gerling, Luis G, Masmitjà, Gerard, Martín, Isidro, Alcubilla, Ramón, Puigdollers, Joaquim, Voz, Cristóbal
• Format: Journal Article
• Language: English
• Published: American Chemical Society 26-08-2019
• Subjects: polymer; PFN; dipole; solar cell; selective contact
• ISSN: 2574-0962; 2574-0962
• DOI: 10.1021/acsaem.9b01055

This work studies a novel electron-selective contact for n-type silicon solar cells based on the modification of the cathode with a polymeric interlayer. Specifically, a thin layer of the conjugated polyelectrolyte PFN is intercalated before the Al contact. During solution-processing, the amine groups in the PFN polymer form intense dipoles by the aggregation of acetate radicals. These dipoles are partially oriented in spin-coated layers because of the different interactions with the substrate and the solvent. As a result, an internal electrostatic potential appears that causes an apparent reduction of the cathode work-function. In this way, electron-selectivity at the rear contact is enhanced by inducing a favorable band-bending near the surface. A significant improvement is obtained in conventional electron-selective contacts with n-doped a-Si:H layers. Furthermore, good-performing solar cells can be also obtained even without intentionally doped layers. Compared to other solutions like the evaporation of metal-fluoride salts, the PFN cathode-modification can be readily done at ambient conditions. Besides, the soft solution-processing kindly preserves the properties of the underlying passivating layers.