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Shunt resistance (RSH) is obtained via reproducing the real photovoltaic performance of organic solar cells based on the full model of the Shockley equation. With an increasing illumination intensity, the RSH of devices decreases markedly, which is attributed to an increase in the free volume of their photoactive layer. The thermal vibration of molecules (polymeric segments) is markedly enhanced under high-intensity illumination (photoexcitation), loosening intermolecular packing and thereby increasing the free volume of the photoactive layer. In addition, the larger surface roughness of the photoactive layer markedly decreases the RSH of the device. Under 1 sun AM 1.5 G illumination, the values of RSH in state-of-the-art organic solar cells are estimated to be about 500–3000 Ω cm2, while under 500 lux illumination, RSH is calculated to be ∼26 000 Ω cm2. This study points out that it is crucial to significantly increase RSH in organic solar cells under illumination, which is very helpful for efficiency improvement under low-intensity illumination and the large-area fabrication of organic photovoltaics. [ABSTRACT FROM AUTHOR]

Organic light emitting diodes using a mixed layer of electron acceptor 3, 4, 9, 10 perylenetetracarboxylic dianhydride and electron donor copper phthalocyanine (PTCDA:CuPc) on indium tin oxide (ITO) anodes were fabricated. The device properties were found to be strongly dependent on the thickness of the PTCDA:CuPc film: both the power efficiency and the driving voltage of the device were optimized with a thickness of PTCDA:CuPc ranging from 10 to 20 nm. As compared to the conventional ITO/CuPc hole injection structure, the ITO/PTCDA:CuPc hole injection structure could remarkably enhance both the luminance and the power efficiencies of devices. A mechanism of static-induced, very efficient hole-electron pairs generation in mixed PTCDA:CuPc films was proposed to explain the experimental phenomena. The structural and optical properties of PTCDA:CuPc film were examined as well. [ABSTRACT FROM AUTHOR]

The study conducted on green phosphorescent organic light-emitting devices (OLEDS) employing tris (2-phenylpyridine) iridium doped in energy gap hole transport host with different thickness of emission layer is presented. The modifications done on P-I-N device structure to obtain maximum power efficiency and low operating voltages is described.

Electron-transporting small molecule bathophenanthroline (Bphen) together with o-xylene has been used as hybrid additives to improve the performance of simplified inverted polymer solar cells employing ITO alone as cathode and photoactive layer based on polymer [[2,6′-4,8-di(5-ethylhexylthienyl)benzo[1,2-b;3,3-b] dithiophene] [3-fluoro-2[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]] (PTB7-Th) and (He et al., Nat. Photon. 9:174, 2015)-phenyl C-butyric acid methyl ester (PCBM). Because the Bphen additive could spontaneously aggregate onto the indium tin oxide (ITO) cathode during spin coating, the mixed solution containing PTB7-Th, PCBM, and Bphen, thereby forming a thin cathode-modifying layer, the ternary blend PTB7-Th:PCBM:Bphen functioned similar to a layered polyethylenimine ethoxylated (PEIE, a conventional cathode-modifying material)/binary blend PTB7-Th:PCBM combination. The o-xylene additive was confirmed to enrich the distribution of PTB7-Th donor towards the bottom area of photoactive layer, thereby benefiting the charge collection in inverted structure. With the o-xylene optimization, the PTB7-Th:PCBM:Bphen blend thin film showed a power conversion efficiency (PCE) of 5.87% in simplified inverted structure of ITO/photoactive layer/MoO/Ag, much higher than that (4.21%) of the PTB7-Th:PCBM blend thin film. The current research can be considered as a useful attempt towards fabricating low-cost photovoltaic devices without marked loss in PCE. [ABSTRACT FROM AUTHOR]