Study on the performance of CuBr2 doped Cs2AgBiBr6 perovskite solar cells with carbon electrode and without a hole-transporting layer

Lead-free double perovskite Cs2AgBiBr6 has attracted much attention due to its environmental stability and low toxicity, which has bee used in photovoltaic devices. Unfortunately, the power conversion efficiency (PCE) is relatively low owing to poor-quality film. In this paper, CuBr2 was added in the precursor to improve the crystalline of the perovskite film. Maybe Cu2+ was reduced to Cu + by DMSO, so Cu + existed in the Cs2(Ag1-xCux)BiBr6 perovskite films. The carbon electrode-based and hole-free solar cells with the planar structure of FTO/c-TiO2/Cs2(Ag1-xCux)BiBr6/C were fabricated. The effect of CuBr2 content on the performance of solar cells were studied. When the content of CuBr was 1 at.%, the solar cell exhibited the optimal PCE of 1.30%, which was increased by 52%, compared with the original solar cell. And the PCE for the planar structure in this work was the highest, compared with that in the other reported works.