http://www.mdpi.com/journal/ijms/special_issues/solar-cells-ijms/ Dear Colleagues, The special issue Solar Cells is dedicated to recent advances made in basic research and technology of solar energy conversion systems. This issue compiles original and review papers covering a broad interdisciplinary spectrum on topics in solid state photodevices, charge carrier dynamics, new photovoltaic materials, quantum-dots based solar cells, nano-dimensioned photo-structures, mimetic systems, hydrogen photogeneration, organic and exiton solar cells and also innovative systems based on silicon technology. Dr. Andrés G. Muñoz Guest Editor Related Special Issues in other Journals Solar Cells in Energies {snippet name="submission_info"} http://www.mdpi.com/1422-0067/12/4/2200/ The determination of optical parameters, such as absorption and extinction coefficients, refractive index and the bandgap energy, is crucial to understand the behavior and final efficiency of thin film solar cells based on hydrogenated amorphous silicon (a-Si:H). The influence of small variations of the gas flow rates used for the preparation of the p-a-SiC:H layer on the bandgap energy, as well as on the dopant elements concentration, thickness and conductivity of the p-layer, is investigated in this work using several complementary techniques. UV-NIR spectrophotometry and ellipsometry were used for the determination of bandgap energies of four p-a-SiC:H thin films, prepared by using different B2H6 and SiH4 fluxes (B2H6 from 12 sccm to 20 sccm and SiH4 from 6 sccm to 10 sccm). Moreover, radiofrequency glow discharge optical emission spectrometry technique was used for depth profiling characterization of p-a-SiC:H thin films and valuable information about dopant elements concentration and distribution throughout the coating was found. Finally, a direct relationship between the conductivity of p-a-SiC:H thin films and the dopant elements concentration, particularly boron and carbon, was observed for the four selected samples. http://www.mdpi.com/1422-0067/12/4/2200/ Wed, 30 Mar 2011 00:00:00 CEST International Journal of Molecular Sciences 2011-03-30 12 4 Article 2200 2215 1422-0067 Characterization of Doped Amorphous Silicon Thin Films through the Investigation of Dopant Elements by Glow Discharge Spectrometry: A Correlation of Conductivity and Bandgap Energy Measurements 2011-03-30 doi: 10.3390/ijms12042200 Pascal Sánchez Olaya Lorenzo Armando Menéndez Jose Luis Menéndez David Gomez Rosario Pereiro Beatriz Fernández http://www.mdpi.com/1422-0067/12/1/476/ This paper introduces the fundamental physical characteristics of organic photovoltaic (OPV) devices. Photoelectric conversion efficiency is crucial to the evaluation of quality in OPV devices, and enhancing efficiency has been spurring on researchers to seek alternatives to this problem. In this paper, we focus on organic photovoltaic (OPV) devices and review several approaches to enhance the energy conversion efficiency of small molecular heterojunction OPV devices based on an optimal metal-phthalocyanine/fullerene (C60) planar heterojunction thin film structure. For the sake of discussion, these mechanisms have been divided into electrical and optical sections: (1) Electrical: Modification on electrodes or active regions to benefit carrier injection, charge transport and exciton dissociation; (2) Optical: Optional architectures or infilling to promote photon confinement and enhance absorption. http://www.mdpi.com/1422-0067/12/1/476/ Mon, 17 Jan 2011 00:00:00 CET International Journal of Molecular Sciences 2011-01-17 12 1 Review 476 505 1422-0067 High Photoelectric Conversion Efficiency of Metal Phthalocyanine/Fullerene Heterojunction Photovoltaic Device 2011-01-17 doi: 10.3390/ijms12010476 Chi-Feng Lin Mi Zhang Shun-Wei Liu Tien-Lung Chiu Jiun-Haw Lee http://www.mdpi.com/1422-0067/12/1/173/ This review focuses on the intrinsic charge transport in organic photovoltaic (PVC) devices and field-effect transistors (SAM-OFETs) fabricated by vapor phase molecular self-assembly (VP-SAM) method. The dynamics of charge transport are determined and used to clarify a transport mechanism. The 1,4,5,8-naphthalene-tetracarboxylic diphenylimide (NTCDI) SAM devices provide a useful tool to study the fundamentals of polaronic transport at organic surfaces and to discuss the performance of organic photovoltaic devices in nanoscale. Time-resolved photovoltaic studies allow us to separate the charge annihilation kinetics in the conductive NTCDI channel from the overall charge kinetic in a SAM-OFET device. It has been demonstrated that tuning of the type of conductivity in NTCDI SAM-OFET devices is possible by changing Si substrate doping. Our study of the polaron charge transfer in organic materials proposes that a cation-radical exchange (redox) mechanism is the major transport mechanism in the studied SAM-PVC devices. The role and contribution of the transport through delocalized states of redox active surface molecular aggregates of NTCDI are exposed and investigated. This example of technological development is used to highlight the significance of future technological development of nanotechnologies and to appreciate a structure-property paradigm in organic nanostructures. http://www.mdpi.com/1422-0067/12/1/173/ Wed, 05 Jan 2011 00:00:00 CET International Journal of Molecular Sciences 2011-01-05 12 1 Review 173 225 1422-0067 Molecular Photovoltaics in Nanoscale Dimension 2011-01-05 doi: 10.3390/ijms12010173 Vladimir Burtman Alexander Zelichonok Andrei V. Pakoulev http://www.mdpi.com/1422-0067/11/12/5027/ We report the synthesis of poly[(3-hexylthiophene)-block-(3-(4,4,5,5,6,6,7,7,7-nonafluoroheptyl)thiophene)], P(3HT-b-3SFT), carried out by the Grignard Metathesis Method (GRIM). The copolymers composition was determined by 1H and 19F NMR spectroscopies, and gel permeation chromatography (GPC). The thin films of P(3HT‑b‑3SFT) were investigated by ultraviolet-visible absorption spectroscopy and atomic force microscopy (AFM). We also fabricated bulk-hetero junction (BHJ) solar cells based on blends of P(3HT-b-3SFT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). Although the composition ratio of P3SFT in P(3HT-b-3SFT) was low, the influence of P3SFT on the morphology and properties of solar cells was significant. The annealing process for the BHJ solar cells induced the formation of large domains and led to poor solar cell performance. The BHJ solar cells, based on PCBM and P(3HT-b-3SFT), prepared by the non-annealing process, had a maximum power conversion efficiency of 0.84% under 100 mW/cm2 (AM 1.5 solar illumination) in air. http://www.mdpi.com/1422-0067/11/12/5027/ Mon, 06 Dec 2010 00:00:00 CET International Journal of Molecular Sciences 2010-12-06 11 12 Article 5027 5039 1422-0067 Poly[(3-hexylthiophene)-block-(3-semifluoroalkylthiophene)] for Polymer Solar Cells 2010-12-06 doi: 10.3390/ijms11125027 Ichiko Yamada Koji Takagi Yasuhiko Hayashi Tetsuo Soga Norio Shibata Takeshi Toru http://www.mdpi.com/1422-0067/11/4/1471/ Fossil fuel alternatives, such as solar energy, are moving to the forefront in a variety of research fields. Organic photovoltaic systems hold the promise of a lightweight, flexible, cost-effective solar energy conversion platform, which could benefit from simple solution-processing of the active layer. The discovery of semiconductive polyacetylene by Heeger et al. in the late 1970s was a milestone towards the use of organic materials in electronics; the development of efficient protocols for the palladium catalyzed alkynylation reactions and the new conception of steric and conformational advantages of acetylenes have been recently focused the attention on conjugated triple-bond containing systems as a promising class of semiconductors for OPVs applications. We review here the most important and representative (poly)arylacetylenes that have been used in the field. A general introduction to (poly)arylacetylenes, and the most common synthetic approaches directed toward making these materials will be firstly given. After a brief discussion on working principles and critical parameters of OPVs, we will focus on molecular arylacetylenes, (co)polymers containing triple bonds, and metallopolyyne polymers as p-type semiconductor materials. The last section will deal with hybrids in which oligomeric/polymeric structures incorporating acetylenic linkages such as phenylene ethynylenes have been attached onto C60, and their use as the active materials in photovoltaic devices. http://www.mdpi.com/1422-0067/11/4/1471/ Thu, 08 Apr 2010 00:00:00 CEST International Journal of Molecular Sciences 2010-04-08 11 4 Review 1471 1508 1422-0067 Acetylene-Based Materials in Organic Photovoltaics 2010-04-08 doi: 10.3390/ijms11041471 Silvestri Marrocchi http://www.mdpi.com/1422-0067/11/1/254/ Dye-sensitized solar cells (DSSCs) were assembled by using the bougainvillea flowers, red turnip and the purple wild Sicilian prickly pear fruit juice extracts as natural sensitizers of TiO2 films. The yellow orange indicaxanthin and the red purple betacyanins are the main components in the cocktail of natural dyes obtained from these natural products. The best overall solar energy conversion efficiency of 1.7% was obtained, under AM 1.5 irradiation, with the red turnip extract, that showed a remarkable current density (Jsc = 9.5 mA/cm2) and a high IPCE value (65% at λ = 470 nm). Also the purple extract of the wild Sicilian prickly pear fruit showed interesting performances, with a Jsc of 9.4 mA/cm2, corresponding to a solar to electrical power conversion of 1.26%. http://www.mdpi.com/1422-0067/11/1/254/ Wed, 20 Jan 2010 00:00:00 CET International Journal of Molecular Sciences 2010-01-20 11 1 Article 254 267 1422-0067 Efficient Dye-Sensitized Solar Cells Using Red Turnip and Purple Wild Sicilian Prickly Pear Fruits 2010-01-20 doi: 10.3390/ijms11010254 Giuseppe Calogero Gaetano Di Marco Silvia Cazzanti Stefano Caramori Roberto Argazzi Aldo Di Carlo Carlo Alberto Bignozzi http://www.mdpi.com/1422-0067/10/11/4575/ Attempts have been made to develop dye-sensitized solar cells based on the principles and materials of photosynthesis: We first tested photosynthetic pigments, carotenoids (Cars), chlorophylls (Chls) and their derivatives, to find sensitizers showing reasonable performance (photocurrent and conversion efficiency). We then tried to introduce the principles of photosynthesis, including electron transfer and energy transfer from Car to Phe a. Also, we tried co-sensitization using the pheophorbide (Phe) a and Chl c2 pair which further enhanced the performance of the component sensitizers as follows: Jsc = 9.0 + 13.8 → 14.0 mA cm–2 and η = 3.4 + 4.6 → 5.4%. http://www.mdpi.com/1422-0067/10/11/4575/ Tue, 27 Oct 2009 00:00:00 CET International Journal of Molecular Sciences 2009-10-27 10 11 Review 4575 4622 1422-0067 Dye-Sensitized Solar Cells Based on the Principles and Materials of Photosynthesis: Mechanisms of Suppression and Enhancement of Photocurrent and Conversion Efficiency 2009-10-27 doi: 10.3390/ijms10114575 Yasushi Koyama Takeshi Miki Xiao-Feng Wang Hiroyoshi Nagae