The photoelectric conversion efficiency（PCE） of perovskite solar cells（PSCs） has reached the level of silicon solar cells

but the main bottleneck restricting its industrialization development is stability. In order to explore the physical law of its attenuation

bulk heterojunction PSCS were successfully fabricated by a new two-step continuous deposition method

and the PCE was 6.73%. This method overcomes the shortcomings of the traditional two-step method

such as the inhomogeneity of perovskite films and the incomplete reaction for the two-step method. The stability of bulk heterojunction PSCs is tested when they are exposed to air for 10

20 and 80 min. It is found that the PCE of bulk heterojunction PSCs decreases gradually

the open circuit voltage of bulk heterojunction PSCs is almost constant

and the short circuit current density and filling factor of bulk heterojunction PSCs decrease gradually. Through the AC impedance test

it is further confirmed that the main reason for the attenuation is the decreasing composite resistance and carrier lifetime for PSCs. The main reason may be that perovskite materials absorb water and oxygen in the air at the grain boundary

leading to its decomposition.