Enhanced Light Harvesting in Mesoscopic Solar Cells by Multilevel Multiscale Patterned Photoelectrodes with Superpositioned Optical Properties

Abstract

Investigations on nano- and micropatterns have been intensively performed in optical applications due to their light modulation effects for enhanced photon utilization. Recently, incorporation of periodic architectures in solar cells have brought signifi cant enhancements in light harvesting and energy conversion effi ciency, however, further improvements in performance are required for practical applications due to the intrinsic limitations of singlelevel patterns. Herein, this study reports mesoscopic solar cells employing photoelectrodes with multilevel multiscale patterns. Polydimethylsiloxane film with multilevel nano/micropatterns (integrated in z-axis direction) is prepared by LEGO-like multiplex lithography, and its architecture is imprinted on mesoporous TiO 2 electrode by soft molding technique. By various spectral analyses and simulations, advanced light harvesting properties by superposition of optical responses from constituent nano- and micropatterns are verifi ed. The effectiveness of the strategy is confi rmed by applications in dye-sensitized solar cells as a model system, wherein over 17.5% increase in effi ciency (by multilevel 400 nm line/20 μm dot structures) is observed. Also, external quantum effi ciencies clearly exhibit that the improved light harvesting originates from the combined effects of diffraction grating and random scattering induced by both nano- and microarchitectures, respectively. Moreover, the validity of the multiscale approach in different dimensions is also confi rmed in order to demonstrate the general advantages. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim