Device Performance Correlated with Structural Properties of Vertically Aligned Nanorod Arrays in Polymer/ZnO Solar Cells

Abstract

Polymer-based solar cells consisting of ZnO nanorods and poly(1-methoxy-4-(2-ethylhexyloxy)-p-phenylenevinylene) (MEH-PPV) are investigated by current−voltage characterization and intensity modulated photovoltage spectroscopy (IMVS). The high quality ZnO nanorod arrays were prepared by electrodeposition, in which the length (L n) and the concentration of deep level defects of ZnO nanorods were controlled by deposition time (T d). Results show that increasing T d leads to ZnO nanorods with linearly increased L n but differently increased defect concentration for the MEH-PPV/ZnO solar cells, providing a peak device power conversion efficiency of 0.34% at AM 1.5 illumination (100 mW/cm2) for T d = 10 min. The electron lifetimes in MEH-PPV/ZnO nanorod devices at open circuit were studied by means of IMVS for the first time, and the influences of L n and defect concentration on the charge recombination kinetics and device performance were revealed. It is found that, in the MEH-PPV/ZnO devices with high quality ZnO nanorods with rather low defect concentration, both photocurrent and recombination rate are mainly dependent on the L n value as a result of the exponential attenuation of incident light intensity in the device, but the open circuit voltage V oc is more sensitive to the defect concentration. The present study provides new insights into designing the nanostructures for the hybrid photovoltaic devices based on vertically aligned one-dimensional nanoarrays.

Influence of Interface Morphology onto the Photovoltaic Properties of Nanopatterned ZnO/Poly(3-hexylthiophene) Hybrid Solar Cells. An Impedance Spectroscopy Study

“…31,33 For solid-state hybrid solar cells, a particular difficulty is that the light-absorbing polymer has to be infiltrated into the already synthesized nanorod array. 28,40 In the case of P3HT as the absorber material, solvent annealing and thermal annealing have…”

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

“…Among the developed nanomaterials, ZnO nanorod arrays, which can be grown vertically from a substrate, have great potential for HPV applications because of their ease of synthesis [7,8] and high electron mobilities (*10 2 cm 2 V -1 s -1 ) [9] with a direct transport pathway to the electrode [10,11]. The ZnO nanorods have been adopted to construct ordered heterojunction HPV devices [12,13] by matching with the most widely used p-type donor in organic-based photovoltaics, poly(3-hexylthiophene) or P3HT [3,14].…”

Effects of Controlling the AZO Thin Film's Optical Band Gap on AZO/MEH-PPV Devices with Buffer Layer

“…These results were attributed to the cascading energy band gap structure of the CdS between AZO and MEH-PPV. This CdS layer could be photoexcited to produce additional photocurrent to improve energy efficiency, similar to in the AZO and MEH-PPV layers [9].…”

“…Efficient separation of charge carriers from their place of generation in the light absorption layers depends on the electron properties of the inorganic material and the morphology of its interface with the polymer [1,2]. Therefore various inorganic semiconductors have been tested to improve efficiency; examples include cadmium selenide (CdSe) nanorods [3] and nanoparticles [4], cadmium sulfide (CdS) nanorods [5] and nanowires [6], ZnO thin film [7] and nanorods [8][9][10], and TiO 2 nanoparticles [11]. Controlling the optical band gap of inorganic materials through the use of Al-doped zinc oxide (AZO) is also promising as these stable thin films have high electron mobility and affinity.…”