Electrical and photoelectrical characteristic investigation of a new generation photodiode based on bromothymol blue dye

Bromothymol blue (BTB) with the molecular formula of C₂₇H₂₈Br₂O₅S was grown onto p-Si substrate to fabricate heterojunction by spin coating technique. The current voltage (I-V) measurements of diode were carried out in dark and under different illumination intensity at room temperature. The photoelectrical properties of heterojunction based on BTB were investigated using the illumination intensity dependent I-V data. The results showed that photo current of diode increases with the increase in light intensity. Also, the electrical parameters of device were determined via I-V, and capacitance- voltage (C-V), conductance-voltage (G-V) measurements at different frequencies. It is observed that the excess capacitance is created at low frequencies due to the contribution of interface states charge which can follow the alternative current signal to capacitance. It is stated that, both the electrical & photoelectrical parameters of diode can be changed, and also the performance of the device could be affected by the organic thin film interlayer.