The impact of surface defects underpins the improved efficiency of hybrid organic/inorganic solar cells

Hybrid solar cells utilize an interface comprising layers of organic and inorganic materials to convert sunlight into electricity. Zinc oxide (ZnO) is a popular choice for the inorganic material because it is cheap, non-toxic and readily available. However, the conversion efficiency of hybrid solar cells using ZnO/organic-donor bulk heterojunctions is currently very low—only 2 percent when ZnO is blended into an organic donor material. On the other hand, a decent 6.1 percent efficiency has been reached when ZnO is used as a layer sandwiched between an electrode and a layer of polymer or small-molecule acceptors.