Ingenieur Vol. 75 ingenieur July 2018-FA - Page 23

Incoming photon T h e m e c h ani s m o f P V electron has been electron Hole left after the Freed ejected phenomena is best explained Incoming photon electron has been electron using fundamental physics. ejected Electron in The fusion of p-type and n-type outer shell semiconductors results in the Electron in Before After collision the silicon atom has a net formation of a p-n depletion region outer shell collision between the photon with the electron positive charge and has lost one of its that ends up with an inverted Before collision between the photon After collision the silicon atom has a net electrons. positive charge and has lost one of its built-in potential. As light quanta with the electron electrons. Figure 4. Photoelectric Effect process. of adequate energy impinge this region, electron-hole pairs are Figure 4. Photoelectric Effect process. Figure 4: Photoelectric Effect process. produced. These are swept by the built-in electric field into the respective sides of the region. When Sunlight Direction of electric an external conducting path is connected across field Sunlight the opposing sides of the p-n device, electricity Direction of electric field flows, thus powering up any device along its path. Metallic All of these are elegantly explained using the grid Back metal Photoelectric Effect, for which Albert Einstein was Metallic contact grid Back metal awarded a Nobel Prize in Physics. Flow of p contact type electrons n type The PV cell is the smallest unit and several Flow of p type of movement of Direction cells are connected in series-parallel to make up electrons n type free electrons Ammeter a PV module. The modules are arranged in series Direction of movement of to form a string whilst strings are combined in Ammeter free electrons Electrical load A parallel to form an array. The present state of PV Electrical load A module conversion technology is listed in Table 1. Figure 5: Completing the loop. Figure 5. Completing the loop. Figure 5. Completing the loop. Table 1: Efficiency of Solar Cells in 2017 (Source https://onlinelibrary.wiley.com/doi/epdf/10.1002/pip.2978) 21