Polymer solar cells (PSCs) have attracted much attention due to their great potentials for large-area, light-weight, flexible, and low-cost devices. Recently, bulk-

heterojunction (BHJ) solar cells based on poly(3-hexylthiophene) (P3HT) and (6,6)-phenyl C61 butyric acid methyl ester (PCBM) with power conversion

efficiency (PCE) of 4-5 % have been reported. However, control of the transportation of the charge carriers at interfaces is one of the most challenging issues in

the improvement of PSCs. It has been reported that the insertion of an interlayer between the organic layer and the anode improves the device performance. To

date, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and transition metal oxides have been employed for this purpose. However, only

the deposition of PEDOT:PSS layer can be easily processed by solution-based coating techniques. Most transition metal oxides as the anode interlayers are

deposited by the vacuum evaporation, which could detract from the advantage of the ease of PSC fabrication. Using solution-processed transition metal oxide as

the anode interlayer for improving the PSC performance has seldom been reported.

The aim of this work is to realize a low-cost and high-efficiency inverted PSC hybridized with ZnO nanorod arrays by introduction of a solution-processed

vanadium oxide (V2O5) as the anode interlayer. Our investigation shows that the photovoltaic device performance is improved by the introduction of the V2O5

interlayer due to the efficient suppression of the leakage currents at the organic/metal interface. Compared to the conventional BHJ structure (indium tin oxide

(ITO)/PEDOT:PSS/active layer/Al), the use of the inverted structure overcomes some obstacles such as the facile oxidation of Al and the electrical

inhomogeneities of PEDOT:PSS as well as its corrosion to ITO. The inverted PSCs utilize an air-stable high work-function electrode as the back contact to

collect holes and metal-oxide nanostructures at the ITO to collect electrons. Furthermore, it has been reported that the ZnO nanorods have beneficial effects of

collecting and transporting electrons in the inverted PSCs hybridized with the ZnO nanorods. Our works combine these advantages of V2O5 interlayer and ZnO

nanorods, which thereby suppress the leakage currents and improve the collection and transportation of the charge carriers, resulting in enhancements of PCE,

open-circuit voltage (VOC), and fill factor (FF) of the devices. In addition, the V2O5 interlayer can serve as an optical spacer to increase light absorption,

leading to an increased short-circuit density (JSC). Moreover, the V2O5 interlayer and ZnO nanorod arrays both are fabricated from simple solution-based

processes, which are well-suited for use in high-throughput roll-to-roll manufacturing.

Although PEDOT:PSS layer can be solution processed, its hygroscopic nature is likely to form insulating patches due to the water adsorption, thus degrading the

devices. In contrast, V2O5 is relatively insensitive to water and stable in air. The solution-processed V2O5 interlayer can serve as a barrier preventing oxygen or

water from entering and degrading the photoactive layer. In addition, this approach does not need annealing treatment like PEDOT:PSS nor vacuum equipments,

so it is simple, expeditious, and effective. This is very important for commercial realization of low-cost and large-area printed solar cells.


Fig 1. (a) Device structure of the photovoltaic cells. (b) Energy band diagram for the photovoltaic cells in this study.


Fig. 2. The J-V curves of the photovoltaic devices with the V2O5 interlayer from various concentrations under 100 mW/cm2 AM 1.5G irradiation.


Fig. 3. (a) AFM images of the photoactive layers covered with and without the optimum V2O5 interlayer. AFM image scans are 5×5 μm.

(b) Transmissionspectrum of the V2O5 layer (from the 100 μg/ml V2O5 colloidal solution) on a glass substrate. (c) XRD spectrum of V2O5.


Fig. 4. (a) IPCE spectra for the devices with and without the optimum V2O5 interlayer.

(b) The change in absorption spectrum [Δα(λ)] and the difference in IPCE spectrum [ΔIPCE(λ)] resulting from the insertion of the optimum V2O5

interlayer. The inset is a schematic of the optical beam path in the both samples. The variables are defined in the text.





,而且具有很大的經濟潛力。在元件結構上,一般是使用塊材異質接面(Bulk-heterojunction)結構,以poly(3-hexylthiophene) (P3HT)為電洞傳輸材

料,(6,6)-phenyl C61 butyric acid methyl ester (PCBM)為電子傳輸材料,利用其具大面積激子分離區域的優點,使元件有較佳的效率。然而,載子


池陽極為例,可以插入poly(3,4-ethylene dioxythiophene):polystyrene sulfonate (PEDOT:PSS)或過渡金屬氧化物作為此用途。然而,只有PEDOT:PSS層





能電池稍不相同。常見的有機太陽能電池結構是氧化銦錫(indium tin oxide, ITO)/PEDOT:PSS/有機主動層/鋁,我們使用的是倒置式結構,此結構以



,使得有機太陽能電池的效率獲得提升。此外,我們發現V2O5中介層也具有optical spacer的功能,可增加光的吸收,進而增加電池的電流密度。

而且,V2O5中介層與ZnO奈米柱陣列均是以簡單的溶液法製備,非常適合捲軸式的製程(roll-to-roll manufacturing)。

雖然PEDOT:PSS層可以溶液態製備,但它具有吸水性,當吸收了空氣中的水氣後會在PEDOT:PSS層內產生insulating patches,使得元件效率下降。




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