Nanostructured p‐n Junctions for Kinetic‐to‐Electrical Energy Conversion

Abstract

Piezoelectric ZnO nanorods grown on a fl exible substrate are combined with the p-type semiconducting polymer PEDOT:PSS to produce a p-n junction device that successfully demonstrates kinetic-to-electrical energy conversion. Both the voltage and current output of the devices are measured to be in the range of 10 mV and 10 μ A cm − 2 . Combining these fi gures for the best device gives a maximum possible power density of 0.4 mW cm − 3 . Systematic testing of the devices is performed showing that the voltage output increases linearly with applied stress, and is reduced signifi cantly by illumination with superband gap light. This provides strong evidence that the voltage output results from piezoelectric effects in the ZnO. The behavior of the devices is explained by considering the time-dependent changes in band structure resulting from the straining of a piezoelectric material within a p-n junction. It is shown that the rate of screening of the depolarisation fi eld determines the power output of a piezoelectric energy harvesting device. This model is consistent with the behavior of a number of previous devices utilising the piezoelectric effect in ZnO.

Control of oxygen vacancies in ZnO nanorods by annealing and their influence on ZnO/PEDOT:PSS diode behaviour

“…To achieve ZnO nanorods with high aspect ratio, one of the most commonly-used methods is to refresh the growth solution to extend the length of the rods, with the assumption that the reaction ceases after around 2.5 h when homogeneous precipitation ceases. 10,13 However, here we have studied a range of synthesis times and precursor concentrations to find the optimum conditions to achieve high-aspect-ratio ZnO nanorods using only a single growth step. Fig.…”

“…The rectification ratio of ZnO nanorod-based diodes with inorganic p-type semiconductors, for example CuSCN, have values of 10 2 -10 4 , while it is less than 10 with organic p-type semiconductors. 5,10,34,[37][38][39] The lower rectification ratio of ZnO diodes using organic p-type materials, such as PEDOT:PSS, has been ascribed to the large leakage current caused by recombination sites or trap states at the interface. 34 Methods to improve the rectification of these diodes would widen their potential applications, taking advantage of the beneficial properties of the organic p-type semiconductors such as low cost, ease of synthesis/coating, flexibility etc.…”

Influence of anneal atmosphere on ZnO-nanorod photoluminescent and morphological properties with self-powered photodetector performance

“…These properties, as well as the relative ease with which ZnO nanostructures can be grown, lend themselves to use in nanoscale field effect transistors, 1 antireflection coatings, 2 energy-harvesting, [3][4][5] and optoelectronic 6,7 devices. ZnO nanorods can be synthesised at low-temperatures (<100 C) using aqueous chemical growth from a variety of chemical precursor mixtures such as zinc nitrate hexahydrate (Zn(NO) 3 Á6H 2 O) and hexamethylenetetramine (HMT).…”

Effects of nanostructure on clean energy: big solutions gained from small features

“…Both the voltage and current output of the devices were measured to be in the range of 10 mV and 10 lA/ cm 2 , respectively. Combining these figures for the best device gave a maximum possible power density of 0.4 mW/cm 3 [73].…”

“…Nanostructured ZnO is reported to be an ideal piezoelectric material with significant improvements in energy harvesting performance [69,73]. For example, piezoelectric ZnO nanorods grown on a flexible substrate are combined with the p-type semiconducting polymer PEDOT: PSS to produce a p-n junction device that successfully demonstrated improved kinetic-to-electrical energy conversion.…”