Cesium iodide (CsI) is attracting attention as a substitute for organic materials such as CH3NH3I. In this work, we fabricated sequential-vacuum-deposited planar heterojunction (PHJ) cesium lead iodide (CsPbI3) perovskite solar cells with enhanced efficiencies by varying the annealing time (0.5, 1, 5, and 10 min). The effect of performance enhancement was investigated as a function of varying annealing time at 350 °C employing a hot plate. The best-performing device was obtained with an annealing time of 1 min, delivered photocurrent density (JSC) of 12.06 mA/cm2, voltage (VOC) of 0.71 V, and fill factor (FF) of 0.67, leading to a power conversion efficiency (PCE) of 5.71% at standard AM 1.5G solar illumination.
We attempt the conformal deposition of CsPbI3 layers on pyramidal-shaped textured crystalline Si (c-Si) surfaces, aiming at application to Perovskite/Si tandem solar cells. CsPbI3 layers are deposited through vacuum evaporation on textured c-Si surfaces with various pyramid sizes. Conformal CsPbI3 layers are formed on the textured c-Si, which is, in principle, difficult to be realized by conventional solution processes. We also confirmed a reduction in the optical reflectance of CsPbI3/Si structures by ∼10% (absolute) by using textured c-Si compared to the case of flat Si. A co-evaporation method can prevent the aggregation of CsI particles, which are seen when the films are formed by sequential evaporation. These results indicate the feasibility of Perovskite/c-Si tandem cells with textured c-Si, leading to low optical reflectivity and a high photocurrent.
We used a two-step
process to fabricate planar perovskite solar
cells (PSCs) in which CH3NH3I (MAI) molecules
intercalated into a PbI2 film. The crystal growth of PbI2 is particularly important to achieve perovskite films with
high PSC performance. Herein, we attempted to control the crystal
growth of PbI2 films through a simple spin-coating method
at annealing temperatures of 70, 150, 250, and 350 °C and times
of 1, 5, 10, and 30 min. We investigate the effects of the high-crystallite
host PbI2 film on the crystallinity, film quality, and
absorption of the resulting MAPbI3 perovskite film as well
as the resulting performance of the planar PSCs. Under the optimal
annealing conditions, a highly crystalline PbI2 film was
reproducibly achieved at 250 °C for 30 min. Precise intercalation
of MAI molecules into the PbI2 film contributed to a smooth
perovskite film and good PSC performance. This work develops a fundamental
understanding of the thermally induced controlled crystal growth of
the parent PbI2 film, which influenced the bridging and
intercalation with MAI, resulting in a high-quality perovskite film.
This study will guide further development based on two-step processes
of perovskite films that have optimal crystallinities and morphologies
that contribute to high PSC performance.
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