Charge-transport and photocurrent generation in bulk hetero junction based on Chloro-aluminum phthalocyanine (ClAlPc) and Rose Bengal (RB)

Bulk-hetero junctions were made with the intermixing of Chloro-aluminum phthalocyanine (ClAlPc) (p-type) and Rose Bengal (RB) (n-type material) from the common solvent. The optical properties of blend reveal that light harvesting is possible from almost entire visible spectrum of the material. The devices were characterized by recording its J–V in dark and under illumination and impedance analysis under various temperatures over wide frequency range, i.e., from 100 Hz to 1 MHz. Various photovoltaic parameters like open circuit voltage (Voc), short-circuit photocurrent (Jsc), and fill factor were evaluated and found to be as 0.92 V and 0.44 mA/cm2 and 0.48, respectively. Also, the effect of thermal annealing on the optical, electrical, and photovoltaic properties of bulk heterojunction device was investigated. From the impedance spectroscopy, we conclude that the change in bulk resistance and dielectric constant of active layer due to the illumination has a direct relevance to the photocurrent generation by the device. The overall observation reveals that upon thermal annealing of the device imparts substantial increase in hole mobility which results in balanced charge transport.