Tandem organic solar cells with a large V OC by control of the active-layer concentration

The tandem organic solar cell could absorb the complementarity sunlight spectra by the sub-cells based on the different energy gap of the active-layer materials. In this work, a wide-band gap of the organic material PTB7-Th: PC 71 BM is used as the front sub-cells active layer, and the narrow-band gap of PTB7-Th: IEICO-4F is used as the rear sub-cells active layer. The front and rear sub-cells present the complementary absorption spectra leading to the sufficiently improvement of the sunlight absorption. MoO 3 /Au/ZnO multilayer film is the interconnecting layer. ZnO film was prepared by the sputtering method is smaller root-mean-square than that of the film prepared by the solution synthesis, resulting in a good contact interfacial between the sub-cells. This is in favor of the J SC and FF of the tandem organic solar cell. Importantly, the short-circuit current density of the tandem solar cell is handily controlled by the active-layer concentration of the front sub-cell, the tandem cell exhibits an optimal PCE of 11.77% with a large V OC of 1.45 V.