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

Abstract

This paper focuses on the characterization of the ZnO/poly(3hexylthiophene) (P3HT) interfaces in nanostructured hybrid solar cells, aiming to elucidate the relationship between thermal treatment, local morphology, and device performance. An equivalent impedimetric model for the device is proposed, allowing us to extract information about the ZnO/P3HT interface morphology and its impact on the photovoltaic properties by comparing devices with and without nanopatterning. It is found that the influence of thermal treatment on performance lies solely in the interface, resulting from a different interfacial morphology of P3HT depending on which crystal direction of ZnO is present.

ZnO Nanorod Arrays as Electron Injection Layers for Efficient Organic Light Emitting Diodes

“…Consequently, much of the NRA design considerations and post-deposition treatments have been governed by their eventual incorporation into hPV devices [21][22][23] .…”

Improving the performance of inorganic-organic hybrid photovoltaic devices by uniform ordering of ZnO nanorods and near-atmospheric pressure nitrogen plasma treatment

“…[1][2][3][4][5][6][7][8] HPV devices promise advantages of both organic and inorganic materials. Organic materials offer high light absorption coefficients, flexibility, ease of processing, and structural diversity.…”

“…9,10 Such NRs are also expected to provide direct pathways to the electrodes after exciton dissociation. Although there have been many efforts to obtain a high density of inorganic NRs, 1,3,5,11,12 the random orientation of the NRs prevents infiltration of the light-absorbing polymer into the NR array. For example, J SC could reach $2.5 mA/cm 2 if the whole surface of ZnO NRs 60 nm in diameter and 600 nm tall contributed to the interface, but only half of the ideal J SC was reached.…”

“…For example, J SC could reach $2.5 mA/cm 2 if the whole surface of ZnO NRs 60 nm in diameter and 600 nm tall contributed to the interface, but only half of the ideal J SC was reached. 3 In addition, the random orientation limits the controllability of the diameter, spacing, and height of the NRs. 13 NRs should be strictly perpendicular to the substrate surface, and the dimensions should be uniform, to increase the donor-acceptor interface area.…”

“…In HPV devices based on conjugated poly(3-hexylthiophene) (P3HT) and ZnO, for example, the V OC estimated from work functions using the electron affinity rule is 1.6 V. 14,15 However, the V OC measured in actual devices is around 0.4 6 0.1 V less owing to recombination losses. [1][2][3]8,9 One possible reason is that the surface of the ZnO has a very narrow depletion region where separated photocarriers (electrons and holes) are very close to each other, allowing their recombination. 16 Another reason is that dark carriers diffuse from the cathode owing to the high electron mobility of ZnO, [17][18][19][20] causing recombination losses between the photocarriers and the dark carriers.…”