Investigation of the effects of MoO3 buffer layer on charge carrier injection and extraction by capacitance-voltage measurement

The effects of MoO3 thin buffer layer on charge carrier injection and extraction in inverted configuration ITO/ZnO/MEH-PPV (poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene))/MoO3 (0, 5 nm)/Ag hybrid solar cells are investigated by capacitance-voltage measurement under dark and light illumination conditions. The efficiency of charge carrier injection and extraction is enhanced by inserting 5 nm MoO3 thin layer, resulting in better device performances. Charge carrier transport of the whole device is improved and the interface energy barrier is reduced by inserting 5 nm MoO3 thin buffer layer. The device fill factor is increased from 54.1 % to 57.5 % after modifying 5 nm MoO3. Simulations and experimental results consistently show that in the forward voltage under dark, the device with the 5 nm MoO3 thin layer modification generates larger value of capacitance than the device without MoO3 layer. While under illumination, the device with the 5 nm MoO3 layer generates smaller value of capacitance than the device without the 5 nm MoO3 layer in the bias region of reverse and before the peak position of maximum capacitance (V (Cmax)). The underlying mechanism of the MoO3 anode buffer layer on device current density-voltage characteristics is discussed.