# “Graphical Solution” for the Solar Cell Conversion Efficiency in the Completely Ideal Case

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## Abstract

The goal of this book is to derive the conversion efficiency under consideration of the equilibrium between the carrier generation and recombination that occurs in the solar cell (i.e., under consideration of the detailed balance principle). As a step toward this goal, we shall first determine the most basic conversion efficiency. The ideal efficiency curve \(u\left( {\nu_{\text{g}} ,T_{\text{s}} } \right)\), which is derived in this chapter, is the basis of all conversion efficiency curves that are presented in the following chapters and thus constitutes an important relation. Besides the mathematical derivation of the ideal efficiency curve \(u\left( {\nu_{\text{g}} ,T_{\text{s}} } \right)\), the present chapter also explains a visual approach, that is, a graphical solution for the efficiency curve, which provides a deeper understanding of \(u\left( {\nu_{\text{g}} ,T_{\text{s}} } \right)\). With this visual approach, the reader can intuitively estimate the value of the ideal solar cell conversion efficiency without the need of solving the equations. In this chapter, we first provide the definition of the solar cell conversion efficiency, and then explain details about the efficiency losses induced by the semiconductor band gap, and finally, we derive the energy conversion efficiency of the ideal solar cell.