A gradient engineered hole-transporting material for monolithic series-type large-area perovskite solar cells

Further efficiency enhancement mainly relies on decreasing the interface losses between the active layers in perovskite solar cells. The design of a gradient engineered hole-transporting material is expected to tune the interface losses in perovskite solar cells. In this work, we reported gradient engineering that afforded the hole-transport material (spiro-OMeTAD) dispersed in the upper part of the perovskite layer. Photoluminescence measurements indicated an enhanced hole extraction from the perovskite-spiro-OMeTAD gradient film. And a maximum PCE of 19.16% and a steady-state efficiency of 18.01% were obtained for the small-area device. Furthermore, we assembled monolithic series-type large-area perovskite solar cells based on gradient engineering. The large-area perovskite solar cell with an active area of 1.01 cm(2) obtained a PCE of 16.61%. Moreover, monolithic series-type large-area perovskite solar cells showed a V-oc of 2.095 V for the binary module and a V-oc of 3.104 V for the ternary module, respectively.