Insulator MnO: Highly efficient and air-stable n-type doping layer for organic photovoltaic cells

The insertion of thin MnO layer between organic photoactive layer and metal electrode significantly improved the power conversion efficiency (PCE) and the air stability of organic photovoltaic cell (OPV). PCE (2.91%) was obtained by inserting 3-nm-thick MnO, higher than 0.91% for the device without MnO, and 2.59% for the device with 0.5-nm-thick LiF. In addition, the PCE of MnO device retained 28.42% of initial value after 2 weeks while the device without MnO dropped down to only 6.03% just after 2 days, even better than that of LiF device which dropped down to 7.29% of initial value after 2 weeks without encapsulation. Insulator MnO is promising to improve the electron transport and operation stability in OPVs.