Cosmos - - Cosmos Science Club -

While the first work­ing pho­to­voltaic (so­lar) cell was made of gold and se­le­nium by Amer­i­can in­ven­tor Charles Fritts in 1883, sil­i­con un­der­pins most so­lar cell tech­nol­ogy to­day and has dom­i­nated since the mid-20th cen­tury.

Sil­i­con so­lar cells pro­duce elec­tric­ity when pho­tons knock elec­trons from one layer of sil­i­con semi­con­duc­tor to an­other. These lay­ers are doped with dif­fer­ent atoms to give one layer an ex­cess of elec­trons and the other a deficit. If the cir­cuit is com­plete, the elec­trons can be cap­tured to pro­duce elec­tric­ity. Many cells bun­dled to­gether form a so­lar panel.

The first sil­i­con so­lar cells’ ef­fi­ciency hov­ered around 5%. Refin­ing sil­i­con’s pu­rity and treat­ing a so­lar cell’s sur­face to bet­ter ab­sorb light have helped boost ef­fi­ciency to around 25%. Com­mer­cially pro­duced so­lar cells cur­rently sit around 20%.

Mean­while, other ma­te­ri­als have been ex­plored for so­lar cells, such as or­ganic semi­con­duc­tors. They’re made mostly made of car­bon and hy­dro­gen atoms.

There are ben­e­fits to or­ganic so­lar cells. Or­ganic semi­con­duc­tors can be printed on flex­i­ble ma­te­ri­als. Plus, they’re cheap.

What they’re not, though, is ter­ri­bly ef­fi­cient. Cur­rent or­ganic so­lar cell tech­nol­ogy has ef­fi­cien­cies around the 10% mark (although this is tipped to rise). So they’re not nec­es­sar­ily seen as a re­place­ment for sil­i­con so­lar cells but can be used along­side them.

For in­stance, or­ganic so­lar cells were in­stalled on rooftops in ru­ral south­ern African vil­lages that couldn’t ac­cess the elec­tric­ity grid, giv­ing those pop­u­la­tions a safer and cheaper al­ter­na­tive to burn­ing kerosene.

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