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Abstract: While sol–gel-processed metal oxides are widely used as an electron transport layer to enhance photovoltaic performances, their effect on photodetector application was not studied. We found sol–gel-processed titanium oxide deteriorated dark current characteristics in reverse biases by almost two orders of magnitude, whereas bare Al cathodes exhibited ideal dark current characteristics. Increased dark current came from space charge limited currents in microscopic p-i-p metal-semiconductor-metal configurations. The spatial variation of workfunction values was believed to form local leakage paths by partial filling of traps on the surface of sol–gel titanium oxide. [Copyright &y& Elsevier]

Abstract: Slot-die coating is one of the promising methods for fabricating large-area polymer solar cells (PSCs) due to its compatibility with roll-to-roll printing and one-dimensional direct patterning. In this study, we investigated correlations between conformal film morphology of intermixed poly(3-hexylthiophene) (P3HT) and fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) bulk-heterojunction (BHJ) material and universal control factors such as shim length, substrate temperature, and coating speed. The observed correlation equation is better matched to the meniscus coating parameter equation rather than to the traditional high-viscosity extrusion slot-die coating parameter equation. Based on our findings regarding the governing factors of the thin film formation of bulk-heterojunction materials, we demonstrated the development of uniform large-area polymer solar cells with power conversion efficiency (PCE) of 3.07% under Air Mass 1.5condition and the possibility of high-throughput production. [Copyright &y& Elsevier]

Abstract: We propose and demonstrate a new series connection method that employs alternating conventional and inverted bulk-heterojunction (BHJ) solar cells. The two adjacent cells in each submodule are connected through top or bottom ‘continuous terminals’ made of aluminum or indium tin oxide (ITO), which are shared by cells with different polarities in either a top-to-top or a bottom-to-bottom manner. In comparison with the conventional series-interconnection method, our new structure offers unique advantages in that both printing methods and efficient coating methods can be applied in the manufacturing of series-connected BHJ photovoltaic modules. [Copyright &y& Elsevier]

Cross-sectional potential distributions of a polymer bulk heterojunction (BHJ) solar cell, consisting of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester blends, were directly observed by using Kelvin probe force microscopy. It was found that the bulk electric field of BHJ is nearly field-free compared with that of classical metal-insulator-metal model, whereas the electric field of BHJ device is confined to the cathode interface. The cathode-interfaced rectification junction is studied to originate from the formation of bilayered p-n junction in the BHJ. [ABSTRACT FROM AUTHOR]

External-biased potential distributions of a polymer bulk-heterojunction (BHJ) solar cell, incorporated with electron/hole transporting layers, were directly obseved through a cross-sectional Kelvin probe force microscopy. The bulk electric field of BHJ was found to be nearly field-free even under reverse biases, and the field-free region was probed to expand with the incorporation of TiOx electron transporting layer; as a result, inducing a decrease of quasi-Fermi level splitting region in obtaining a high fill factor in the TiOx-interlayered junction photodiodes. [ABSTRACT FROM AUTHOR]

Cross-sectional potential distribution of high open-circuit voltage bulk heterojunction photovoltaic device was measured using Kelvin probe force microscopy. Potential drop confined at cathode interface implies that photo-active layer is an effective p-type semiconductor. Potential values in field-free region show wide variation according to log-normal distribution. This potential dip prone to have holes captured during the diffusive motion, which can increase bimolecular recombination, while potential gradient in depletion region makes this potential dip smaller and the captured holes easily escape from dip region by Schottky barrier lowering. [ABSTRACT FROM AUTHOR]

Abstract: Electro-spray (e-spray) is emerging as an attractive printing method for the thin-film fabrication of organic materials because of the simple apparatus and its high efficiency. Here, we demonstrate a fully e-sprayed organic solar cell (OSC) with high performance by using an additive in the poly(3-hexylthiophene):[6,6]-phenyl C61-butyric acid methyl ester (P3HT:PCBM) layer without any post-processing treatment. The P3HT:PCBM film fabricated with 6vol% 1,8-diiodooctane (DIO) showed improved surface macro- and nano-morphologies, which resulted in an enhanced photovoltaic performance. Using optimized conditions, we obtained a 2.98% efficient OSC (as-prepared condition) with the e-spray method, and post-annealing increased the power conversion efficiency (PCE) slightly to 3.08%. [Copyright &y& Elsevier]