Device Performance Related to Amphiphilic Modification at Charge Separation Interface in Hybrid Solar Cells with Vertically Aligned ZnO Nanorod Arrays

Abstract

This paper reports the chemical modification effects at charge separation interface on the performance of the hybrid solar cells consisting of poly(2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) as an electron donor (D) and vertically aligned ZnO nanorod arrays as an electron acceptor (A). Results show that, with increasing the modification time T s for grafting dye Z907 onto the ZnO surface from 0 to 8 h, the charge transfer efficiency at the MEH-PPV/ZnO interface keeps increasing, the short circuit current (J sc ) increases and reaches a peak value at T s = 8 h, but the open circuit voltage (V oc ) increases within T s = 1-3 h and reduces with further increasing T s up to g6 h. By controlling the T s , a peak power conversion efficiency of η = 0.61% at AM 1.5 illumination (100 mW/cm 2 ) is obtained for T s = 6 h. It is revealed that the Z907 modification mainly contributes to the enhanced J sc by increasing the charge separation efficiency as a result of the improved electronic coupling property at the D/A interface rather than the light harvesting; on the other hand, the Z907 modification reduces (T s = 1-3 h) or increases (T s g 6 h) the surface defect concentration of the ZnO nanorods, resulting in the increased or reduced V oc (or electron lifetime τ e ). It is demonstrated that trapping electrons by the surface defects may facilitate the charge separation at the D/A interface in the MEH-PPV/ZnO devices, and both V oc and τ e correlate to the occupation of injected electrons in conduction band and surface defects. Further analysis provides the relation between V oc and τ e in those devices.

One-dimensional ZnO nanostructures: Solution growth and functional properties

“…The PCBM probably serves as an offset stepping layer that enhances effective carrier transport. Similar studies have also been reported on an amphiphilic grafted dye molecule that not only bridged between hydrophilic ZnO nanowires and hydrophobic polymers, but also assisted interfacial electron cascade transportation by enhancing the electronic coupling between the polymer LUMO and the ZnO conduction band [487,488]; Third is that the processing parameters such as the polymer infiltration, the solvent used, and the annealing temperature/ atmosphere were not optimized [489][490][491]. In an attempt to further enhance the efficiency, ZnO/TiO 2 heterojunctions have also been used in hybrid solar cells to facilitate the charge separation and transport [492,493].…”

Efficient and stable CH3NH3PbI3-sensitized ZnO nanorod array solid-state solar cells

“…2), which is much better than comparable values found in ssDSCs based on ZnO nanorod arrays. 11,22 The light intensity dependence of J sc and V oc was investigated in the CH 3 NH 3 PbI 3 /ZnO nanorod devices, see Fig. 5a and b.…”

CdS and CdSe quantum dots subsectionally sensitized solar cells using a novel double-layer ZnO nanorod arrays

“…As a new class of photoelectrode materials for photovoltaic devices, the well aligned one-dimensional ZnO nanostructures, such as nanorods (NRs) and nanowires (NWs), have been widely investigated as photoelectrodes for dye-sensitized solar cells (DSSCs), due to the large surface area to adsorb more sensitizer and the direct electrical pathway to ensure the rapid collection of carriers generated by optical excitations [1][2][3][4][5]. However, nanostructured metal oxide photoelectrodes, such as ZnO and TiO 2 , are facing the major limitation of poor visible light absorption.…”