Multi-layering of a nanopatterned TiO2 layer for highly efficient solid-state solar cells

Jongbeom Na,Eunkyoung Kim,Younghoon Kim,Chihyun Park

doi:10.1038/am.2015.105

Abstract

A facile process to prepare multi-layered nanopatterned photoanodes (MNPs) is presented with well-arrayed mesoporous inorganic oxide layers. The MNPs were prepared with multiple stacking of nanopatterned TiO2 layers using a sacrificial polystyrene (PS)-thin film layer, which not only guided the stacking TiO2 layer but also was removed completely by calcination without generating cracks. The prepared MNPs exhibited large enhancement of the light harvesting property by increasing the number of nanopatterned TiO2 layers, through multiple reflection of the incident light from the periodic embedded channels formed between the nanopatterned layers. The photovoltaic efficiency was optimized with a 3-layered nanopatterned photoanode exhibiting a 73% Jsc and a 65% power conversion efficiency enhancement compared with a cell with a flat TiO2 layer for I2-free solid-state dye-sensitized solar cells. Korean researchers have developed a multilayered, nanopatterned photoanode that traps significantly more light than conventional devices. Dye-sensitized solar cells based on titanium dioxide (TiO2) are an emerging low-cost photovoltaic technology, but efficiency gains must be made before they can be used in practical applications. Eunkyoung Kim and colleagues from Yonsei University in Seoul investigated ways to enhance light reflectivity in dye-sensitized solar cells by using a polydimethylsiloxane stamp to form nanoscale channels into a TiO2 paste. After removing the nanostamp and performing annealing, they coated the patterned TiO2 with a sacrificial polystyrene film that preserved the periodic channels when the stamping process was repeated. The team produced a three-layered TiO2 nanoarchitecture that captured light transmissions normally lost as waste, resulting in a 65% gain in photoconversion efficiency over flat TiO2 layers. A facile process to prepare multi-layered nanopatterned photoanodes (MNPs) is presented with well-arrayed mesoporous inorganic oxide layers. The MNPs were prepared by multiple stacking of nanopatterned TiO2 layers using a sacrificial polystyrene-thin film layer, which not only guided the stacking TiO2 layer but also was removed completely by calcination without generating cracks. The MNPs were applied to solid-state solar cells, to exhibit an enhancement of 73% and a 65% in Jsc and power conversion efficiency (PCE), respectively.

Highlights

Micro- and nano-patterned structures have demonstrated unprecedented light modulation effects; these structures have received considerable attention in metamaterial structures[1] and various light harvesting devices.[2,3,4,5,6,7,8,9,10]. In this context, patterned photoanodes in solar cells have been studied as a line structure,[11] a 3D micro-pyramid,[12] an embedded micro-line,[13] and moth-eye structures[14] in an effort to improve light harvesting efficiency in photovoltaic devices.[2,3,15]
Among the various solar cells, iodine-free solid-state dye-sensitized solar cells based on a conductive polymer as hole transporting materials have been attracting much interest recently owing to their low toxicity, light overall weight, long-term durability and processibility.[11,22,23]
Nanostructures and morphologies of multi-layered nanopatterned photoanodes (MNPs) The MNPs were prepared via multiple stacking of nanopatterned TiO2 layers using sacrificial PE-thin film layers, each of which was removed upon calcination after the stacking of the subsequent nanopatterned TiO2 layer onto the bottom TiO2 layer

Summary

Introduction

Micro- and nano-patterned structures have demonstrated unprecedented light modulation effects; these structures have received considerable attention in metamaterial structures[1] and various light harvesting devices.[2,3,4,5,6,7,8,9,10] In this context, patterned photoanodes in solar cells have been studied as a line structure,[11] a 3D micro-pyramid,[12] an embedded micro-line,[13] and moth-eye structures[14] in an effort to improve light harvesting efficiency in photovoltaic devices.[2,3,15] In addition, the photonic crystal[7,16,17] and plasmonic nanostructures[18,19] have been explored intensively. Patterned structures exhibit enhanced surface area and are able to trap the incident light to enhance light harvesting;[20,21] patterned structures are a key component in a solar cell.

Methods

Results

Conclusion