(The) effect of nitrogen-doped carbon nanotubes on charge transport in perovskite solar cells

Abstract

The organic-inorganic hybrid perovskite emerged as one of the most promising solar cell material due to its superior optoelectronic properties. However, solution-processed polycrystalline perovskite film shows inferior electronic properties because of their structural defects. In addition, formamidinium-based perovskite has longer hole diffusion length than electron diffusion length, which leads to charge accumulation in the device. Here, I introduced N-doped carbon nanotubes (N-CNTs) into the perovskite layer for solar cell application. Different from undoped CNTs which has no selectivity of charge, N-CNTs extract and transport photoelectron selectively. N-CNTs were used as charge transport channels in the perovskite layer, reducing the resistance in the perovskite device and improving the efficiency compared to the reference device by 12.3%. In addition, as the electron transport is improved, it is confirmed that the charge accumulation is reduced by balancing with the fast hole transport, and the amount of perovskite active layer which was limited due to the short electron diffusion length has been successfully increased. The modification in electron mobility by N-CNTs can be further applied for other perovksite optoelectronic devices to enhance the perovskite electrical properties.