Controlled Morphology of ZnO Nanorods for Electron Transport in Squaraine Bulk‐Hetero Junction Solar Cells With Thick Active Layers

Abstract

The influence of ZnO seed layer thickness in Squaraine (SQ) is investigated: PC71BM bulk heterojunction solar cells that incorporate ZnO nanorods. The thickness of the ZnO seed layer varies between 16–249 nm by changing the concentration of the precursor solution. With atomic force microscopy (AFM), X‐Ray Diffraction (XRD), and Scanning Electron Microscopy (SEM) studies, it is shown that this approach allows to systematically tune the thickness of the ZnO seed layer without influencing seed layer grain size, or the morphology of the ZnO nanorods that are deposited on top of the seed layer. The proof‐of‐concept is demonstrated in SQ:PC71BM solar cells. It is found that seed layers with 55 nm thickness yield the highest short circuit current densities, resulting in power conversion efficiencies of 2.5 ± 0.1%. These results are compared to SQ:PC71BM solar cells prepared in planar architectures, and it is observed that both device architectures yield comparable results. The optimized nanostructured ZnO electrode enables the fabrication of BHJ devices with thick active layers without the loss in solar cell performance.

Control of Surface Defects in ZnO Nanorod Arrays with Thermally Deposited Au Nanoparticles for Perovskite Photovoltaics

“…ZnO-NR and ZnO-NR/Au samples were fabricated according to the procedure described in the Experimental Section. Briefly, ZnO-NR were deposited using chemical bath deposition (CBD) via ZnO seeding on ITO substrates. − Decoration of the ZnO-NR with Au nanoparticles was achieved by thermally depositing a thin Au layer on top of the nanorods with the sample kept at room temperature, leading to the formation of small (<10 nm) individual Au nanoparticles distributed over the ZnO-NR array. We investigated ZnO-NR/Au samples prepared with Au effective layer thicknesses of 0.4, 0.8, and 1.2 nm.…”

“…ZnO-NR were subsequently prepared by deposition in a solution of 25 mM of zinc nitrate hexahydrate and 25 mM hexamethylenetetramine (molar ratio 1:1) in Milli-Q water (18 MΩ·cm) . The solutions were prepared according the procedure below.…”

ZnO Nanorods: An Advanced Cathode Buffer Layer for Inverted Perovskite Solar Cells

“…ZnO-NR growth only occurs along the [002] plane and is therefore robust against slight variations in crystallinity of the seed layer. The NR morphology, small diameter size, and [002] crystal orientation allow the targeted optimization of the solar cell hole blocking layer …”

“…The NR morphology, small diameter size, and [002] crystal orientation allow the targeted optimization of the solar cell hole blocking layer. 35 As charging recombination centers, the agglomerations of metal oxide on the surface produced a rough surface and an intragap state with a significant volume. 36 It was reported that the charge collection was more efficient in the NR-based photoelectrodes.…”

Facile Fabrication of SnO2 Nanorod Arrays Films as Electron Transporting Layer for Perovskite Solar Cells

“…As reported, one dimensional (1D) nanostructures could offer a straightforward pathway for electron transport, a wide space for effective pore filling of perovskites or hole transport materials, and a large surface area for carrier extraction, thus improving the photovoltaic performance of PSCs . Up to now, different kinds of 1D TiO 2 structures, such as nanorods, nanocone, nanowires, and nanotubes, have been used in PSCs.…”