Effects of the morphology of nanostructured ZnO and interface modification on the device configuration and charge transport of ZnO/polymer hybrid solar cells

Abstract

In an organic-based solar cell, the short exciton diffusion length of organic materials requires effective donor-acceptor heterojunction at the nanoscale. In this work, hybrid inorganic/polymer solar cells based on ZnO nanostructures and poly(3-hexylthiophene) (P3HT) are constructed to study the effects of ZnO morphologies and wettability of the surface on the P3HT infiltration ability and charge transport mechanisms. The P3HT infiltrates the ZnO nanorod (NR) more remarkably than ZnO nanoparticle (NP) substrates. Although surface modification with indoline D205 dye molecules improves the wettability (viz. enlarges the contact angle) of NP surface, the P3HT infiltration distance decreases in comparison with the pristine NP case. This leads to relatively low short-circuit current density (Jsc) of the NP devices in comparison with that of the NR devices, even though the surface area of NP layers is larger than that of NR ones. Moreover, surface modification with squaraine dye onto the NR surface shows more significant improvement in Jsc than the NP case. This is due to the well-aligned morphology of the NRs, which facilitates dye modification, P3HT infiltration, and charge transport processes. These indicate that the NRs are more qualified as electron accepting substrates and transport pathway in hybrid solar cells than NPs.

Control of charge dynamics by blending ZnO nanoparticles with poly(3-hexylthiophene) for efficient hybrid ZnO nanorods/polymer solar cells

“…3, and the photovoltaic parameters are summarized in Table 1. The photovoltaic parameters of the ZnO nanorods/P3HT HPV device of the previously reported literature [21] are used as a reference sample for comparison. It is seen that short-circuit current density (J sc ) of the HPV devices increase systematically upon the addition of ZnO nanoparticles.…”

“…Sol-gel and hydrothermal processes have been carried out to grow ZnO nanorods on indium tin oxide (ITO) substrates [20,21,36]. First, a solution of zinc acetate (91.63 mg cm -3 ) and monoethanolamine (30.50 mg cm -3 ) in 2-methoxyethanol was prepared and deposited onto the cleaned ITO substrates by spin-coating.…”

“…ZnO nanoparticles were synthesized and purified using the procedures reported elsewhere [21,[37][38][39]. A 60 cm 3 portion of KOH solution in methanol (24.67 mg cm -3 ) was added dropwise into a 120 cm 3 portion of zinc acetate dihydrate solution in methanol (24.58 mg cm -3 ) within 10 min.…”

“…The issue behind the low PCE is the inefficient charge transfer and charge generation, which are intensively influenced by the morphology of HPV devices [3,20]. In our previous report [21], we compared morphological effects of ZnO nanorods and ZnO nanoparticles on photovoltaic performance. We found that the rod-to-rod space of ZnO nanorod substrate is in a range of \10-80 nm, which is greater than the pore size of ZnO nanoparticle substrate (a few nanometers to a maximum of 55 nm).…”

Photophysical Behaviors at Interfaces between Poly(3-Hexylthiophene) and Zinc Oxide Nanostructures

“…Poly(3-hexylthiophene) (P3HT) is a conventional conjugated polymer applied in OSC as donor in the active layer 4,5) . As a candidate of inorganic semiconductor, ZnO is famous for its multiple nanostructures, which have high carrier mobility and ambient stability 6,7) . Photoinduced electron transfer occurs at the interface between the polymer (donor) and the inorganic semiconductor (acceptor) and results in ef cient charge separation.…”