Effect of Copper Sulfide nanocrystals in a Poly(3-hexylthiophene)/Titania solar cell

Abstract

ABSTRACTPoly(3-hexylthiophene)/Titania (P3HT/TiO2) heterojunction has been widely studied in the field of hybrid solar cells. Usually, organic dyes shift the neat TiO2 absorption edge toward the visible range improving the conversion efficiency or/and the TiO2 surface is modified with ligands in order to increase the electron transport. On the other hand, copper sulfide, non-toxic semiconductor, has been included in bulk organic P3HT based solar cell, increasing the photocurrent density of devices. Therefore, we propose the use of copper sulfide in the hybrid TiO2/P3HT heterojunction to determine its effect in the performance of TiO2/P3HT solar cell. Copper sulfide nanocrystals (CuxS) were synthesized at 230 °C, 240 °C and 260 °C and, they were mixed with P3HT in order to form P3HT:CuxS bulk heterojunctions. Scattered grains and irregular morphology in the final topography of the reference device (P3HT/TiO2 heterojunction) were observed by AFM, while a granular morphology and a few pores like craters were observed in the devices containing P3HT:CuxS bulk heterojunctions. Chalcocite phase (Cu2S) was obtained at 230 and 240°C and, digenite (Cu1.8S) phase at 260°C, both copper sulfide phases are very promising for solar cells. Despite this, poor rectifications in the devices were found in the current-voltage curves of the devices containing copper sulfide nanocrystals in contrast to the P3HT/TiO2 cell (device without nanocrystals), it could be due to the current leakage or recombination process in the copper sulfide/TiO2 interface. It suggests future work in order to improve the devices.