Organic thin film solar cells (OTFSCs) were fabricated with blended active layers of poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]] (PTB7)/[6,6]-phenyl-C71-butyric (PC71BM). The performances of active layers are prepared in chlorobenzene (CB) with different additives of 1-chloronaphthalene (CN) and 1,8-Diiodooctane (DIO) by a wet process with spin coating technique. The effects of different solvent additives on photovoltaic parameters such as fill factor, short circuit current density, and power conversion efficiency of active layers are reported. The absorption and surface morphology of the active layers are investigated using UV-visible spectroscopy and atomic force microscopy, respectively. The results indicate that structural and morphological changes were induced by the additives with solvent. The current density-voltage (J-V) characteristics of photovoltaic cells were measured under the illumination of simulated solar light with 100 mW/cm2(AM 1.5 G) by an Oriel 1000 W solar simulator. The OTFSCs of PTB7/PC71BM prepared with organic solvent additives of DIO+CN show more improved PCE of 4.96% by spin coating method.
Bulk heterojunction (BHJ) structure based active layers of PCDTBT/PC71BM were prepared by using different organic solvents for fabrication of organic solar cell (OSC) devices. Mixture of precursor solutions of PCDTBT/PC71BM in three different organic solvents was prepared to fabricate composite active layers by spin-coating process: chloroform; chlorobenzene; o-dichlorobenzene. Four different blend ratios (1 : 3–1 : 6) of PCDTBT: PC71BM were adopted for each organic solvent to clarify the effect on the resulting OSC device characteristics. Surface morphology of the active layers was distinctively affected by the blend ratio of PCDTBT/PC71BM in organic solvents. Influence of the blend ratio of PCDTBT/PC71BM on the OSC device parameters was discussed. Performance parameters of the resulting OSC devices with different composite active layers were comparatively investigated. Appropriate blend ratio and organic solvent to achieve better OSC device performance were proposed. Furthermore, from the UV-Vis spectrum of each active layer prepared using the PCDTBT/PC71BM mixed solution dissolved with different organic solvents, a possibility that the nanophase separation structure inside their active layer could appear was suggested.
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