On doubts about Mott–Schottky plot of organic planar heterojunction in photovoltaic cell

The work presents small signal spectra of complex capacitance obtained on an organic photovoltaic cell with a heterojunction formed from di-(pyridyl)-perylenetetracarboxylic diimide and bromophosphorus phthalocyanine in the 25 Hz–1 MHz frequency range. The real part of capacitance is also presented in the Mott–Schottky plot at various frequency values. It is shown that although an organic heterojunction in a photovoltaic cell can lead to a straight line in the Mott–Schottky plot the parameters obtained in this way cannot be treated as unique since, unlike semiconductor devices, they depend on frequency.