Improved exciton dissociation and charge transport in energetically cascaded trilayer organic solar cells

We demonstrate improved exciton dissociation and charge transport in trilayer organic solar cells (OSCs). The interlayer with an intermediate energy level between the main donor and acceptor levels assists the dissociation of excitons in the charge transfer state (CT) and aids the charge transport by increasing a CT state energy. Additionally, the total absorption of the OSC was increased due to the complementary absorption of the inserted interlayer. Experimentally, when a chloroaluminum phthalocyanine (ClAlPc) layer was inserted between copper phthalocyanine (CuPc) and C60 in a trilayer OSC, the internal quantum efficiency (IQE) was greatly enhanced by 30% in the wavelength range of 350-550 nm. The enhancement of IQE results in an increase of the power conversion efficiency from 1.30% to 1.69%.