Novel ZnO nanostructured electrodes for higher power conversion efficiencies in polymeric solar cells

Ajuria, Jon; Etxebarria, Ikerne; Azaceta, Eneko; Tena‐Zaera, Ramón; Montcada, Núria F.; Palomares, Emilio; Pacios, Roberto

doi:10.1039/c1cp22830g

Cited by 32 publications

(44 citation statements)

References 21 publications

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“…233 It was found that, by modifying the ZnO NW array with a thin layer of ZnO NPs by immersing in a ZnO colloidal suspension, improved P3HT:PCBM blend penetration was achieved (Fig. 16d and 16e).…”

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confidence: 95%

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ZnO cathode buffer layers for inverted polymer solar cells

Liang

Zhang

Jiang

et al. 2015

Energy Environ. Sci.

286

218

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This article provides an overview on the design, fabrication and characterization of the most widely used cathode buffer layers (CBLs) constructed with pristine zinc oxide (ZnO), doped-ZnO, and ZnO-based composites as well as the surface modified ZnO-based CBLs for the improvement of power conversion efficiency (PCE) and long-term device stability of inverted polymer solar cells (PSCs). To achieve high PCE in inverted PSCs, the selection of an appropriate material to form the high quality CBL so as to optimize the electron collection and transport is particularly important. Among the different materials for CBL in inverted PSCs, ZnO has attracted most extensive research in view of its relatively high electron mobility, optical transparency, ease synthesis with versatile morphologies via low cost solution methods at low temperatures, and being environmentally stable. The research has revealed that the electronic processes at the interface between ZnO CBL and polymer active layer play an important role in determining the solar cells performance, and such processes are related to the ZnO CBL in terms of its morphology, microstructure, doping and surface modification. This review attempts to give a general review to better understand the impacts of (1) morphology, (2) thickness, (3) nanostructures, (4) doping, (5) surface modification and (6) composition/hybrids of ZnO CBLs on the solar cells performance. The fundamental understanding of the rapid progress of interfacial engineering made in PSCs would also be beneficial to the development of perovskite solar cells due to similar energy level and device structures.Fig. 12 (a) Schematic illustration of device structure with ZnMgO CBL. (b) Energy levels of the components in the inverted PSCs with various ZMO CBLs. (c) Optical absorption spectra of ZMO films. The inset shows an increase in the bandgap of ZMO films with the increasing of Mg content (x). (d) J-V curve of the device with the ZMO ( x = 0.3) CBL. 48 Fig. 13 (a) Chemical structures of PTB7-Th, PC 71 BM and BisNPC60-OH, (b) Schematic illustration of the proposed cathode interlayer from XPS depth profile; (c) Energy levels diagram for ZnO, InZnO, ZnO-BisC60 and InZnO-BisC60 determined from ultraviolet photoelectron spectroscopy (UPS) and UV-Vis results and for all the components in the inverted PSCs.

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confidence: 95%

“…227 (b) Hydrothermal two-growth ZnO nanorods. 239 FE-SEM micrographs of (c) ZnO nanowires and magnified views of (d) as-electrodeposited and (e)ZnO nanoparticles modified ZnO nanowires 233. …”

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confidence: 99%

ZnO cathode buffer layers for inverted polymer solar cells

Liang

Zhang

Jiang

et al. 2015

Energy Environ. Sci.

286

218

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“…Then, the cell is short-circuited and the decay in the photocurrent is measured and integrated to obtain the extracted charge. 31,32 In other words, this time domain technique can be regarded as being complementary to IS. Thus, CE also provides information on how the system stores charges.…”

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Charge carrier transport and contact selectivity limit the operation of PTB7-based organic solar cells of varying active layer thickness

et al. 2013

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In this work we study the different electrical loss pathways occurring during the operation of bulk heterojunction solar cells by using a variety of electrical and optical characterization techniques beyond the current density-voltage curve (J-V): Impedance Spectroscopy (IS), Charge Extraction (CE) and Transient Photovoltage (TPV). Two sets of devices are analyzed: the first is based on the donor polymer P3HT, known to provide efficient cells using thick active layers (i.e. 270 nm), and the recently developed PTB7 which offers maximum efficiencies for devices with thinner layers (i.e. 100 nm). Devices fabricated with P3HT:PC 60 BM are not limited by transport of carriers and large active layer thickness may be used.Importantly, increasing the active layer thickness does not modify the contact selectivity. This is supported by analysis of the diode curve measured in the dark (similar leakage currents) and by capacitance-voltage measurements (similar fullerene content covering the cathode). Under these conditions the current density curve under illumination is mainly defined by the recombination processes taking place in the bulk of the active layer. In contrast, transport of carriers and contact selectivity are both limiting factors for the PTB7:PC 60 BM system. In this case, best efficiencies are obtained with a low active layer thickness and a high fullerene ratio. Reduced active layer thickness minimizes undesired electrical resistances related to carrier transport through the bulk of the active layer. High fullerene content enhances the amount of fullerene molecules at the cathode leading to decreased leakage currents. Then, the overall device efficiency will be a combination of the recombination kinetics in the bulk of the active layer, undesired resistance to transport of carriers and leakage current present due to low selectivity of the contact. The use of additives has also been explored which enhances charge generation and extraction. Overall, this work provides a comprehensive guide on how to interpret results obtained from some of the most widely used optoelectronic techniques employed to analyse operating devices.

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“…Some clear strategies would include the control of the surface of the nanorods, which has been shown to play an important role in hybrid cells[45-49], the deposition of a highly conformal top blocking layer (such as PEDOT:PSS [50] or WO 3 [51]) and the improvement of the conformal top contact coverage. In addition, optimising the blend thickness and tailoring the spacing and dimensions of the nanorods will enable further improvements in the IQE and EQE [52].…”

Section: Resultsmentioning

confidence: 99%

Nanostructured conformal hybrid solar cells: a promising architecture towards complete charge collection and light absorption

et al. 2013

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We introduce hybrid solar cells with an architecture consisting of an electrodeposited ZnO nanorod array (NRA) coated with a conformal thin layer (<50 nm) of organic polymer-fullerene blend and a quasi-conformal Ag top contact (Thin/NR). We have compared the performance of Thin/NR cells to conventional hybrid cells in which the same NRAs are completely filled with organic blend (Thick/NR). The Thin/NR design absorbs at least as much light as Thick/NR cells, while charge extraction is significantly enhanced due to the proximity of the electrodes, resulting in a higher current density per unit volume of blend and improved power conversion efficiency. The NRAs need not be periodic or aligned and hence can be made very simply.

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Novel ZnO nanostructured electrodes for higher power conversion efficiencies in polymeric solar cells

Cited by 32 publications

References 21 publications

ZnO cathode buffer layers for inverted polymer solar cells

ZnO cathode buffer layers for inverted polymer solar cells

Charge carrier transport and contact selectivity limit the operation of PTB7-based organic solar cells of varying active layer thickness

Nanostructured conformal hybrid solar cells: a promising architecture towards complete charge collection and light absorption

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