Affiliation:
1. Dipartimento di Ingegneria dell'Informazione Università di Pisa via G. Caruso 16 Pisa 56122 Italy
2. Surflay Nanotec GmbH Max‐Planck‐Straße 3 12489 Berlin Germany
3. Physics Department University of Pisa Largo Pontecorvo 3 Pisa I‐56127 Italy
4. CISUP Centro per l'Integrazione della Strumentazione dell'Università di Pisa Lungarno Pacinotti 43 Pisa I‐56126 Italy
Abstract
AbstractMiniaturized solid state capacitors leveraging migration of unipolar ions in a single polyelectrolyte layer sandwiched between metal electrodes, namely, polyelectrolyte capacitors (PECs), have been recently reported with areal capacitance up to 100–200 nF mm−2. Nonetheless, application of PECs in consumer and industrial electronics has been hindered so far by their small operational frequency range, up to a few kHz, due to the resistive behavior (phase angle >−45°) of PECs in the range kHz‐to‐MHz. Here, it is reported on multilayer polyelectrolyte capacitors (mPECs) that leverage as dielectric an ambipolar nanometer‐thick (down to 10 nm) stack of anionic and cationic polyelectrolytes assembled layer‐by‐layer between metal electrodes to eliminate the resistive behavior at frequencies from kHz to MHz. This significantly extends the operational range of mPECs over PECs. mPECs with areal capacitance as high as 25 nF mm−2 at 20 Hz and full capacitive behavior from 100 mHz to 10 MHz are demonstrated using different assembling conditions and anionic/cationic polyelectrolyte pairs. The mPECs reliably operate over time for >300 million cycles, at different biasing voltages up to 3 V, and temperatures up to 80 °C, showing a reversible capacitive behavior without significant hysteresis. Application of mPECs in flexible electronics, also operating at high frequency, is envisaged.