Controlling of silicon–insulator–metal junction by organic semiconductor polymer thin film

Abstract

Electrical and photovoltaic properties of a metal–semiconductor–insulator–polymer–metal diode were investigated. The n-Si/SiO 2/MEH-PPV/Al diode shows a rectifying behavior with the rectification ratio of 2.22 × 10 5 at ±5 V and exhibits a non-ideal behavior due to the series resistance and oxide-organic layers. The organic semiconductor makes a contribution to the I– V characteristics of the diode and the trap-charge limited space charge and space charge limited current mechanisms were observed for the diode. The current–voltage characteristics of the n-Si/SiO 2/MEH-PPV/Al diode under different illumination intensities give an open circuit voltage ( V oc) along with a short circuit current ( I sc). This suggests that the n-Si/SiO 2/MEH-PPV/Al diode is a photovoltaic device with V oc = 0.456 V and J sc = 7.89 × 10 −8 A/cm 2 values under 100 mW/cm 2 illumination intensity. The photoconductivity mechanism of the diode is controlled by monomolecular recombination. The interface state density D it values with time constant τ it of the diode under dark and illumination conditions were found to be 2.53 × 10 10 eV −1 cm −2 with 5.09 × 10 −5 s and 2.50 × 10 10 eV −1 cm −2 with 8.27 × 10 −5 s, respectively. The obtained results indicate that the n-Si/SiO 2/MEH-PPV/Al diode is a photo-sensitive diode.