Electrical and photovoltaic characteristics of sodium copper chlorophyllin/n-type silicon heterojunctions

Heterojunctions of p-type sodium copper chlorophyllin (p-SCC)/n-type silicon (n-Si) were prepared by deposition of p-SCC film on n-Si wafers using spray-pyrolysis technique. Current-voltage and capacitance-voltage measurements of Au/p-SCC/n-Si/In heterojunctions were performed to discuss the electrical properties of these heterostructures. Rectifying characteristics were observed, which are definitely of the diode type. The current-voltage measurements suggest that the forward current in these junctions involves tunnelling and the results showed that the forward current can be explained by a multi-tunnelling capture-emission model in which the electron emission process dominates the carrier transport mechanism. On the other hand, the reverse current is probably limited by the same conduction process. The capacitance-voltage behavior indicates an abrupt heterojunction model is valid for Au/p-SCC/n-Si/In heterojunctions and the junction parameters such as, built-in potential, V_D, carrier concentration, N, the width of depletion layer, W, were obtained. The temperature and frequency dependence of the measured capacitance were also studied. The loaded I-V characteristics under white illumination provided by tungsten lamp (80 mW/cm²) give values of 400 mV, 0.9 mA, 0.38 and 1.7% for the open-circuit voltage, V_oc, the short-circuit current, I_sc, the fill factor, FF, and conversion efficiency, η, respectively.