Cesium Carbonate as an Electron Transport Layer in Polymer Solar Cells

A study published in China investigated the use of solution-processed Cs₂CO₃ as an electron transport layer in inverted polymer solar cells. After light annealing for 15 minutes, the device achieved a power conversion efficiency (PCE) of 8.35%, with a short-circuit current density of 15.8 mA/cm², an open-circuit voltage of 0.76 V, and a fill factor of 69.5% — reported as the highest fill factor for PTB7-based polymer solar cells at the time.

XPS analysis showed that Cs₂CO₃ converts to Cs₂O and CO₂ during light annealing. Control experiments using different irradiation times, as well as vacuum-deposited Cs₂CO₃, produced similar efficiencies, confirming that light annealing is a simple and effective method for improving polymer solar cell performance.

Reference: Light publishing. 2014.Series 11