Abstract
The effect of a new transition metal oxide, rhenium oxide (ReO3), on the performance of polymer solar cells based on regioregular poly(3-hexylthiophene) (P3HT) and methanofullerene [6,6]-phenyl C61-butyric acid methyl ester (PCBM) blend as buffer layer was investigated. The effect of the thickness of ReO3 layer on electrical characteristics of the polymer solar cells was studied. It is found that insertion of ReO3 interfacial layer results in the decreased performance for P3HT: PCBM based solar cells. In order to further explore the mechanism of the decreasing of the open-circuit voltage (Voc), the X-ray photoelectron spectroscopy (XPS) is used to investigate the ReO3 oxidation states. Kelvin Probe method showed that the work function of the ReO3 is estimated to be 5.13eV after thermal evaporation. The results indicated the fact that a portion of ReO3 decomposed during thermal evaporation process, resulting in the formation of a buffer layer with a lower work function. As a consequence, a higher energy barrier was generated between the ITO and the active layer.
Highlights
Organic solar cells are promising candidates for clean energy and have the advantages of flexibility and low production cost, compared to their inorganic counterparts [1,2]
The J-V curve for device with Indium tin oxide (ITO)/PEDOT: poly(styrene sulfonate) (PSS) as buffer layer is shown for comparison
The incident photon-to-current conversion efficiency (IPCE) spectra of photovoltaic cells compare very well with those previously reported for P3HT: phenyl C61-butyric acid methyl ester (PCBM) blend films
Summary
Organic solar cells are promising candidates for clean energy and have the advantages of flexibility and low production cost, compared to their inorganic counterparts [1,2]. Works on the cell structure modification and insertion of buffer layer material between ITO and the active layer have been reported to improve the short circuit current density (Jsc) in the polymer solar cell. The efficiency of polymer photovoltaic cells is greatly improved when poly(ethylenedioxythiophene) (PEDOT) doped with poly(styrene sulfonate) (PSS) is used as a buffer layer. The function of PEDOT: PSS is to prevent electron leakage from the bulk heterojunction (BHJ) acceptor to the anode, to enhance photo-generated hole extraction, and to planarize the ITO surface. Recently many researchers have found that PEDOT: PSS has many disadvantages. They are highly acidic (PH~1) and corrosive to the PLOS ONE | DOI:10.1371/journal.pone.0133725. They are highly acidic (PH~1) and corrosive to the PLOS ONE | DOI:10.1371/journal.pone.0133725 July 30, 2015
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