Abstract
The importance of solar energy can never be over-emphasized. Photovoltaic conversion is the most convenient method for harnessing solar energy. The demand for solar electricity has been increasing in this power hungry world. This has challenged the existing technology for solar power and motivated researchers to find innovative solutions. High cost and high technology have always been highlighted in the context of solar photovoltaics. Due to high cost, during the initial period, solar cells could be employed only in high end applications such as space technology. For widespread use of solar cells, it is imperative to bring the cost of harnessing solar energy down to an affordable level. Efforts taken for over more than 50 years on this topic are reviewed in this paper. These include the search for low cost materials and technology, using amorphous, nanocrystalline materials or thin films, and efforts to increase the conversion efficiency. The concept of spectrum modification is the most ingenious scheme for increasing the efficiency, which ultimately can help bring down the cost.
Highlights
“Among thin film solar cells, Cu(In, Ga)Se2 (CIGS) and Cadmium telluride (CdTe) solar cells have achieved conversion efficiencies over than 21%, and commercial devices have been prepared successfully.”[210]. In general, the grain boundaries are considered detrimental to solar cell performance since they cause recombination of charge carries produced by absorption of solar radiations
Some of the factors affecting solar cell efficiency are (i) at the most one e–h pair is generated in the semiconductor even for photon energies exceeding Eg and 2Eg and (ii) all the photogenerated carriers do not contribute to photoconversion, but some of them are lost in recombinations
Summarizing, if we look at the excitation spectra of various phosphors reported for spectrum modification, we see that all earlier data consist of a wavelength region too short to be of practical importance
Summary
In terms of photovoltaic (PV) conversion, it is estimated that “by covering only 0.4% of the earth’s surface with photovoltaic (PV) panels of an efficiency of 15%, our energy demand can be satisfied.[2] If the extraterrestrial solar radiation is 1367 W/m2 Even at the smallest scale (W), it is useful, e.g., for charging portable devices such as cell phones, tabs, digital cameras, calculators, etc Notwithstanding these limitations, a wide range of applications[3,4] including water heating, air heating, solar furnaces,[5] air conditioning of buildings, solar refrigeration,[6] desalination,[7] green houses, power generation,[8] and photo-biological conversions have been envisaged for solar energy. There are several ways of harnessing solar energy such as solar thermal, solar thermochemical, solar chemical (photosynthesis), solar photovoltaic (SPV), etc
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