1. Solar cell efficiency refers to the portion of energy in the form of sunlight that can be converted via photovoltaics into electricity.
2. The Efficiency of any process is a measure of how well the process works.That is, how much effort you need to put in to get an out put. The input is energy from Sunlight, and the output is energy in electrons.
Maximum Power Point Ultimate Efficiency
https://en.wikipedia.org/wiki/Solar_cell_efficiency (1.); http://sciencing.com/calculation-solar-cell-efficiency-23767.html (2.)
Author: Anas Naddour