Incident photon-to-current efficiency of thermally treated SWCNTs-based nanocomposite for dye-sensitized solar cell

Abstract

This study focuses on incident photon-to-current efficiency (IPCE) performance of In2O3-SWCNTs for dye-sensitized solar cell (DSSC) application. The thin films were prepared by sol-gel method using spin-coating technique annealed at 400, 450, 500, 550, and 600 °C. Morphology transition of In2O3 from spherical to cubic and then octahedral structure occurred as the annealing temperature rises. The photoanode annealed at 450 °C (cubic structure) provides a stable phase of cubic structure with large surface area and optimum thickness for effective dye adsorption. However, the IPCE value does not solely depends on the dye adsorption of photoanodes (light harvesting efficiency (LHE)) but the electron injection efficiency (ηinj) and the collection efficiency (ηcoll). Smaller energy bandgap of photoanodes favors the injected electrons with higher driving force to the conduction band (CB) of the photoanode, which in turn increases the ηinj from the LUMO of dye to the In2O3-SWCNTs CB. Besides that, the absence of single-walled carbon nanotubes (SWCNTs) above 500 °C caused the energy bandgap to increase and leads to lower driving force of injected electrons. In addition, SWCNTs are capable of absorbing visible light faster than other materials. Therefore, the cubic structure-based photoanode (450 °C) exhibited better electron transport with larger driving force on injected electron (ηinj) that decreased the electron recombination rate and increased electron lifetime and subsequently obtained larger charge collection efficiency (ηcoll) of almost 99%. Consequently, the IPCE performance of DSSC was enhanced. [Figure not available: see fulltext.] © 2018 Springer-Verlag GmbH Germany, part of Springer Nature