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.