Efficient Planar Heterojunction Perovskite Solar Cells via Low-Pressure Proximity Evaporation Technique

The sequential deposition process is widely used to fabricate planar structure perovskite solar cells because of better uniformity and perfect surface coverage of perovskite films. However, it is difficult to control the crystallization of perovskite finely. Here, we improve the sequential deposition process by using a low-pressure proximity evaporation technique. The slow grain growth rate of perovskite (CH
₃
NH
₃
PbI
₃
) would make large crystallization and high quality of perovskite film. Moreover, we manipulate an innovative double-side interdiffusion process, that is, sequentially deposit CH
₃
NH
₃
I/PbI
₂
/CH
₃
NH
₃
I to fabricate the perovskite layer. This way, PbI
₂
can be effectively converted into perovskite from a double side and achieve good control of CH
₃
NH
₃
I deposition on the surface as well. The devices reach an efficiency over 14%, which is the first time for TiO
₂
free cells fabricated by a low-pressure approach.