**1. Introduction**

26 Solar Cells – New Aspects and Solutions

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of Cathode Confinement on the Performance of Polymer/Fullerene Photovoltaic Cells in the Thermal Treatment, *IEEE Transaction on Electron Devices*, Vol. 58, No. 3, PVC Photovoltaic solar cells are unanimously recognized to be one of the alternative renewable energy sources to supplement power generation using fossils. It is also recognized that semiconductors layered films technology, in reducing production costs, should rapidly expand high-scale commercialization.

Despite the excellent achievements made with the earliest used materials, it is also predicted that other materials may, in the next few decades, have advantages over these front-runners. The factors that should be considered in developing new PVC materials include:


Silicon-based cells as well as the recently experimented polymer and dye solar cells could hardly fit all these conditions. Transparent conducting oxides as ZnO, SnO2 as well as doped oxides could be good alternative candidates.

In this context, the optothermal expansivity is proposed as a new parameter and a guide to optimize the recently implemented oxide monolayer spray-grown solar cells.
