Making of the solar cell in ambient atmosphere

Dye Sensitized Solar Cells are by far the most popular type of organic solar cells in terms of the number of research papers, the documented attempts of commercialization, and the general awareness of the technology.....perhaps more disputable reason could be that they are quite simple to prepare using simple equipment and readily available materials. DSSCs have been prepared by school classes employing window glass, white paint, a kitchen oven, and some sort of colored dye from berries or wine.

In this work we demonstrate a nanostructured polymer hybrid solar cell with excellent operational stability that can be prepared in the ambient atmosphere by simple means. There is a requirement for materials with a certain level of complexity but there are no requirements for vacuum or inert processing conditions......this example can be used by school or university classes for the preparation and demonstration of the polymer and hybrid solar cell technology.....The manipulations were carried out at an ambient temperature of 20±2 ◦C and a relative humidity of 35 ± 5%.

Substrates
Conducting indium tin oxide (ITO) substrates were employed. Rigid glass substrates with a 100 nm layer of ITO and a sheet resistivity of 8–12 Ω square−1 were purchased from Lumtec and were cleaned by consecutive ultrasonication in acetone, water, and isopropanol for 5 min, followed by drying immediately prior to use. The flexible substrates were purchased from Delta Technologies and comprised 200 μm
polyethyleneterephthalate (PET) foil with an overlayer of ITO and a sheet resistivity of 25–35 Ω square−1.


The zinc oxide nanoparticles were prepared by a procedure similar... In a typical run starting from Zn(OAc)2·2H2O (29.7 g) in methanol (1250 ml) heated to 60 ◦C, KOH (15.1 g) dissolved in methanol (650 ml) heated to 60 ◦C was added over 30 s. The mixture became cloudy towards the end of the addition. The mixture was heated to gentle reflux, and after 2–5 min the mixture became clear and was stirred at this temperature for 3 h, during which time precipitation starts. The magnetic stirring bar was removed and the mixture left to stand at room temperature for 4 h. The mixture was carefully decanted, leaving only the precipitate. The precipitate was then resuspended in methanol (1 l) and allowed to settle for 16 h. The methanol was removed by decantation, making sure that the precipitate was drained as well as possible without letting it dry. Chlorobenzene (40 ml) was added immediately and the precipitated nanoparticles dissolved gradually over 15 min, giving a total volume
of 60 ml. The concentration was typically in the range 150–225 mg ml−1. After determination of the zinc oxide concentration, methoxyethoxyacetic acid (MEA) was added. The best range of MEA concentration was found to be 4–6% w/w with respect to zinc oxide. Concentrations as high as 20% w/w were employed and gave the highest stability for the zinc oxide nanoparticle solutions.


A simple nanostructured polymer/ZnO hybrid solar cell—preparation and operation in air, Krebs et al 2008 Nanotechnology 19 424013

The solar cell can be prepared entirely in the ambient atmosphere by solution processing without the use of vacuum coating steps, and it can be operated in the ambient atmosphere with good operational stability under illumination (1000 W m-2, AM1.5G, 72 ± 2 °C, 35 ± 5% relative humidity) for 100 h with a 20% loss in efficiency with respect to the initial performance. The dark storability (darkness, 25 °C, 35 ± 5% relative humidity) has been shown to exceed six months without notable loss in efficiency. The devices do not require any form of encapsulation to gain stability, while a barrier for mechanical protection may be useful. The devices are based on soluble zinc oxide nanoparticles mixed with the thermocleavable conjugated polymer poly-(3-(2-methylhexan-2-yl)-oxy-carbonyldithiophene) (P3MHOCT), which through a thermal treatment is converted to the insoluble form poly(3-carboxydithiophene) (P3CT) that generally gives stable polymer solar cells. The devices employed a solution based silver back electrode. One advantage is that preparation of the devices is very simple and can be carried out by hand under ambient conditions, requiring only a hot plate that can reach a temperature of 210 °C, and preferably also a spincoater. This type of device is thus excellently suited for teaching and demonstration purposes provided that the materials are at hand.

http://www.iop.org/EJ/abstract/0957-4484/19/42/424013