Hierarchical Nanostructures for Solar Cells - Hierarchical Nanostructures for Energy Devices - page 59

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CHAPTER 4
Hierarchical Nanostructures
for Solar Cells

JUNYEOB YEO* AND SEUNG HWAN KO

Applied Nano and Thermal Science (ANTS) Lab, Department of
Mechanical Engineering, Seoul National University, 1 Gwanak-ro,
Gwanak-gu, Seoul 151-742, Korea
*Email: [e-mail]

4.1 Introduction
Developing sustainable renewable energy sources has been a major research
topic to solve the environmental and limited resource problems of fossil
fuels. Significant progress has been made to increase eciencies in various
renewable energy technologies including solar cells, fuel cells, nuclear
energy, wind power and so on. 1 Among them, solar energy has been regarded
as the most reliable clean energy source due to a large abundance of solar
energy. 2 Solar cell devices have already been developed over the five
decades. 1 However, the widespread use of solar cells is limited by two major
challenges: conversion eciency and cost. 1 The single crystalline bulk
silicon solar cell was the first generation solar cell and it is the most widely
used on the market due to its high conversion eciency. However, because
of the considerably high material costs, second generation solar cells (thin
film solar cells) have been developed to address production costs. 1 To lower
the production costs further, third generation solar cells (nanostructured
inorganic-organic hybrid and organic solar cells) have emerged as a prom-
ising approach to e cient solar energy conversion. 1 The nanostructured
inorganic-inorganic hybrid (dye-sensitized solar cell (DSSC)) and organic

.