Capacitance–voltage extraction method for the deep-level defect distribution in organic photodiode

This paper proposes a method to extract deep-level trap states of the organic photodiode by capacitance–voltage (CV) measurement. The relationship between the trapped charge density and the surface potential can be determined by solving Poisson's equation, while employing Gauss's theorem to establish a correlation between the charge density and the CV characteristics. Consequently, deep-level trap states can be analytically obtained by the conventional CV measurement. Experimental results on P3HT:PCBM devices demonstrate that the deep trap distribution obtained by this method can be well connected with the capacitance–frequency method. Furthermore, our CV method yields a total trap concentration, which closely aligns with that obtained through Mott–Schottky relation. In conclusion, this method provides an effective approach for quantifying deep trap state density of organic photodiode.