UV-Ozone Treatment on Cs2CO3 Interfacial Layer for the Improvement of Inverted Polymer Solar Cells

Inverted configuration polymer solar cells (IPSCs) were prepared by using Cs2CO3 modified indium tin oxide (ITO) substrates as cathode and MoO3/Al as anode, ITO/Cs2CO3/P3HT:PCBM/MoO3/Al. The interfacial Cs2CO3 layers were conducted with annealing treatment and different time UV-Ozone treatment. The power conversion efficiency (PCE) of IPSCs was improved to 1% when the UV-Ozone treatment time is 15 minutes, with the open-circuit voltage of 0.48 V, short-circuit current density of 5.4 mA/cm2, and fill factor of 39%. The improvement of IPSCs should be attributed to the increased electron transporting and collection ability of Cs2CO3 layer induced by UV-Ozone treatment. The underlying mechanism of PCE improvement was discussed in terms of series and shunt resistance of cells induced by UV-Ozone treatment on Cs2CO3 layer, and the mole ratio of Cs to O of Cs2CO3 layer with different UV-Ozone treatment was investigated by scanning electron microscopy operating in the mode for in situ energy dispersive X-ray (EDX) spectra