Air-stable inverted flexible polymer solar cells using zinc oxide nanoparticles as an electron selective layer

The performance and stability of unencapsulated inverted bulk-heterojunction solar cells with zinc oxide (ZnO) made by different processes as the electron selective contact are compared to conventional bulk-heterojunction solar cells. The low temperature processed inverted devices using ZnO nanoparticles on indium tin oxide plastic substrates showed high power conversion efficiency of ∼ 3.3 % . This inverted device structure possessed much better stability under ambient conditions retaining over 80% of its original conversion efficiency after 40 days while the conventional one showed negligible photovoltaic activity after 4 days . This is due to the improved stability at the poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/Ag interface.