Photovoltaic performance analysis of organic device based on PTCDA/n-Si heterojunction

Thin films of 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA) were prepared by thermal evaporation technique under high vacuum at room temperature (300 K). The prepared films were identified by scanning electron microscopy (SEM), and X-ray diffraction (XRD). The capacitance-voltage (C-V) characteristics of PTCDA/n-Si heterojunction was measured at different temperatures ranging from 300 to 400 K under dark condition. The dependence of C^-2 on V for the device PTCDA/n-Si was found to be almost linear which indicates that the junction is abrupt and then the essential junction parameters were obtained. The built-in potential and the acceptor carrier concentration are found to be strongly temperature dependent. Capacitance was also measured under illumination of 100 mW/cm² condition in the temperature range 300-400 K. The capacitance of the device is found to increase with increasing illumination intensity due to the irradiated light induced electron-hole pairs in the depletion region as well as the decrease in the depletion layer. The dark current density-voltage (J-V) characteristics show the rectification effect which may be due to the formation of junction barrier at PTCDA/n-Si interface. The photovoltaic characteristics were determined by analyzing the dependence of short circuit photocurrent density J_SC and the open circuit voltage V_oc on the illumination intensity at different temperatures. PTCDA is useful material to be used in photovoltaic devices.