cy ▁of ▁several ▁companies , ▁as ▁prices ▁for ▁conventional ▁sil icon ▁cells ▁decl ined ▁rapidly ▁in ▁recent ▁years . ▁However , ▁C IG S ▁solar ▁cells ▁have ▁become ▁as ▁efficient ▁as ▁mult ic ry st all ine ▁sil icon ▁cells — the ▁most ▁common ▁type ▁of ▁solar ▁cells . ▁C IG S ▁and ▁C d Te - P V ▁remain ▁the ▁only ▁two ▁commer cially ▁successful ▁thin - film ▁techn ologies ▁in ▁a ▁glob ally ▁fast - g row ing ▁P V ▁market . ▁ ▁Other ▁thin ▁films ▁▁ ▁In ▁phot ov olta ics ▁" th in ness " ▁generally ▁is ▁in ▁reference ▁to ▁so - called ▁" first ▁generation " ▁high - e ffic iency ▁sil icon ▁cells , ▁which ▁are ▁manufact ured ▁from ▁bulk ▁w af ers ▁hundreds ▁of ▁mic rom eters ▁thick . ▁Th in ▁films ▁sacrifice ▁some ▁light ▁gather ing ▁efficiency ▁but ▁use ▁less ▁material . ▁In ▁C IG S ▁the ▁efficiency ▁trade off ▁is ▁less ▁severe ▁than ▁in ▁sil icon . ▁The ▁record ▁effic ien cies ▁for ▁thin ▁film ▁C IG S ▁cells ▁are ▁slightly ▁lower ▁than ▁that ▁of ▁C IG S ▁for ▁lab - scale ▁top ▁performance ▁cells . ▁In ▁ 2 0 0 8 , ▁C IG S ▁efficiency ▁was ▁by ▁far ▁the ▁highest ▁compared ▁with ▁those ▁achieved ▁by ▁other ▁thin ▁film ▁techn ologies ▁such ▁as ▁cad m ium ▁tell ur ide ▁phot ov olta ics ▁( C d Te ) ▁or ▁am orph ous ▁sil icon ▁( a - Si ). ▁C IS ▁and ▁CG