Hydrothermally grown ZnO electrodes for improved organic photovoltaic devices

Abstract

A B S T R A C THere we report a simple, solution based processing route for the formation of large surface area electrodes resulting in improved organic photovoltaic devices when compared with conventional planar electrodes. The nanostructured electrode arrays are formed using hydrothermally grown ZnO nanorods, subsequently infiltrated with blends of poly(3-hexylthiophene-2,5-diyl) (P3HT) and indene-C 60 bisadduct (IC 60 BA) as photoactive materials. This well studied organic photoactive blend allows the composition/processing/performance relationships to be elucidated. Using simple solution based processing the resultant nanostructured devices exhibited a maximum power conversion efficiency (PCE) of 2.5% compared with the best planar analogues having a PCE of around 1%. We provide detailed structural, optical and electrical characterization of the nanorod arrays, active layers and completed devices giving an insight into the influence of composition and processing on performance. Devices were fabricated in the desirable inverse geometry, allowing oxidation resistant high work-function top electrodes to be used and importantly to support the hydrothermal growth of nanorods on the bottom electrode -all processing was carried out under ambient conditions and without the insertion of a hole transport layer below the anode. The nanorods were successfully filled with the active layer materials by carrying out a brief melt processing of a spin-cast top layer followed by a subsequent thermal anneal which was identified as an essential step for the fabrication of operational devices. The growth method used for nanorod fabrication and the active layer processing are both inherently scalable, thus we present a complete and facile route for the formation of nanostructured electron acceptor layers that are suitable for high performance organic active layers.

Revisiting the Optical Dispersion of Aluminum‐Doped Zinc Oxide: New Perspectives for Plasmonics and Metamaterials

“…[ 1,2 ] Due to its unique features, such as wide direct bandgap at room temperature, large binding energy, high transparency, environment‐friendly properties, and, most importantly, low cost and ease of fabrication, it has continuously been a central component of photovoltaic thin films, optoelectronic devices, and even daily applications such as pharmaceutics and cosmetics. [ 3–6 ] Hence, an investigation about a direct usage of this compound for plasmonic purposes, via manipulating its material characteristics, provides new horizons for future research and applications.…”

Structural and Optical Properties of ZnO Thin Films Prepared by Molecular Precursor and Sol–Gel Methods

“…These properties saw ZnO thin films fabricated for various industrial applications, e.g., in optoelectronic devices [3], lasers, gas sensors, and ultraviolet (UV) light emitters [4], and as protective surface coatings [5]. ZnO plays important roles in a number of solar cell systems, such as silicon-based solar cells (first-generation), thin films (second generation), and organic multi-junction, dye-sensitized (third-generation) systems, either as a transparent conductive oxide (TCO) or as a junction for exciton separation [6].…”

Fabrication of ZnO Thin Film through Chemical Preparations

“…In solar cells, ZnO plays important roles in collecting the energy from sunlight in various solar cells such as silicone-based solar cell (first-generation solar cell), thin film (secondgeneration), organic, multijunction, dye-sensitized (third-generation), hybrid and perovskite solar cells (fourth generation). In the first to the third generation of solar cell, ZnO plays a role as transparent conductive oxide (TCO), except in organic solar cell in which ZnO acts as a junction for exciton separation [3].…”