DyeSentitised Solar Cells

Energy is the basic need of all economies, whether developed or developing. For the past two centuries electricity requirements have been provided mostly by fossil fuels, which have two basic limitations: being non-renewable and environmentally damaging. Considering the ever-increasing demand for electricity that is expected to peak in the coming years1 it has become imperative to explore alternative sources of energy which are not only renewable but also eco-friendly. Of these, the use of solar energy has been found to be practical and viable. The solar energy available to Earth is 3×1024 J/year, which is 104 times of present global energy requirements.2 Hence, devices to enable capture and conversion of solar energy into electrical energy, termed as solar or photovoltaic (PV) cells, have been a field of ongoing research interest. As a result, recent years have witnessed considerable advances in the development of the design and efficiency of PV cells.

PV cells are based on the principle of natural means of solar energy fixation or photosynthesis followed by green plants as illustrated by figure 1. The fixed chemical energy is utilized by the plant for various energy-requiring processes. Thus, the photovoltaic effect discovered in 1839 by Becquerel, refers to the generation of electricity due to light irradiation upon two electrodes attached to a solid or liquid system.3 PV cells are therefore based on charge separation at the interface of two materials having distinct conduction. Developments in the field of PV cells has until now been concentrated in the use of junction devices made of inorganic solid materials, primarily silicon and other semiconductor mediums such as cadmium telluride, copper indium gallium selenide (CIGS), etc. However, the third generation of PV cells utilizes organic materials, such as thin films of nanocrystalline, and conductive polymers, which provide two key advantages – higher efficiency and lower cost of fabrication, along with several others.