Photovoltaic properties of the organic–inorganic photodiode based on polymer and fullerene blend for optical sensors

Inorganic–organic photodiode was fabricated with blend single layer as well as sandwich structure, using p-Si and poly(2-methoxy-5-(20-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV):fullerene-C60 blend. Electronic parameters such as barrier height, diode ideality factor, series resistance and shunt resistance were determined from the I–V characteristic in the dark of p-Si/C60:MEH-PPV diode and were found to be 0.75 eV, 1.36, 6.26 × 105 Ω, 1.40 × 1010 Ω, respectively. The interface state density and time constant of p-Si/C60:MEH-PPV diode were determined to be 2.55 × 1011 eV−1 cm−2 and 1.81 × 10−6 s, respectively. The photoconductivity sensitivity and responsivity values of the diode were found to be 8.16 × 10−6 S m/W and 1.63 × 10−2 A/W, respectively. The p-Si/C60:MEH-PPV diode indicates a photovoltaic behaviour with a maximum open circuit voltage Voc of 130 mV and short-circuit current Isc of 24.5 nA. The photocurrent of the device was found to be 2.94 μA and photoconductivity mechanism of the p-Si/C60:MEH-PPV diode indicates the existence of continuous distribution of trap centres. It is evaluated that the p-Si/C60:MEH-PPV photovoltaic device can be operated as a heterojunction photodiode.