Controllable Growth of Perovskite Films by Room-Temperature Air Exposure for Efficient Planar Heterojunction Photovoltaic Cells

A two‐step solution processing approach has been established to grow void‐free perovskite films for low‐cost high‐performance planar heterojunction photovoltaic devices. A high‐temperature thermal annealing treatment was applied to drive the diffusion of CH3NH3I precursor molecules into a compact Pb...

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Published in:Angewandte Chemie (International ed.) 2015-12, Vol.54 (49), p.14862-14865
Main Authors: Yang, Bin, Dyck, Ondrej, Poplawsky, Jonathan, Keum, Jong, Das, Sanjib, Puretzky, Alexander, Aytug, Tolga, Joshi, Pooran C., Rouleau, Christopher M., Duscher, Gerd, Geohegan, David B., Xiao, Kai
Format: Article
Language:English
Subjects:
Air exposure
Air temperature
Annealing
Crystal defects
Crystal structure
Crystallinity
Degree of crystallinity
Diffusion layers
Diffusion length
Heat treatment
Heterojunctions
Interdiffusion
in situ X-ray diffraction
Performance degradation
Perovskites
Photovoltaic cells
photovoltaic devices
Photovoltaics
Radioactivity
Room temperature
SOLAR ENERGY
Temperature
thin films
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Summary:A two‐step solution processing approach has been established to grow void‐free perovskite films for low‐cost high‐performance planar heterojunction photovoltaic devices. A high‐temperature thermal annealing treatment was applied to drive the diffusion of CH3NH3I precursor molecules into a compact PbI2 layer to form perovskite films. However, thermal annealing for extended periods led to degraded device performance owing to the defects generated by decomposition of perovskite into PbI2. A controllable layer‐by‐layer spin‐coating method was used to grow “bilayer” CH3NH3I/PbI2 films, and then drive the interdiffusion between PbI2 and CH3NH3I layers by a simple air exposure at room temperature for making well‐oriented, highly crystalline perovskite films without thermal annealing. This high degree of crystallinity resulted in a carrier diffusion length of ca. 800 nm and a high device efficiency of 15.6 %, which is comparable to values reported for thermally annealed perovskite films. A breath of fresh air: Simple room‐temperature air exposure can drive the interdiffusion between perovskite precursor layers and crystallize the perovskite thin films. The obtained perovskite films show high crystallinity and well‐aligned orientation. The devices with and without a TiO2 electron transporting layer yielded high efficiencies of 15.6 % and 13.8 %, respectively.
ISSN:1433-7851
1521-3773
DOI:10.1002/anie.201505882