Abstract
The role of Cl in halide hybrid perovskites CH3NH3PbI3(Cl) (MAPbI3(Cl)) on the augmentation of grain size is still unclear although many reports have referred to these phenomena. Herein, we synthesized MAPbI3(Cl) perovskite films by using excess MACl-containing precursors, which exhibited approximately an order of magnitude larger grain size with higher <110>-preferred orientation compared with that from stoichiometric precursors. Comprehensive mechanisms for the large grain evolution by Cl incorporation were elucidated in detail by correlating the changes in grain orientation, distribution of grain size, and the remaining Cl in the perovskite during thermal annealing. In the presence of Cl, <110>- and <001>-oriented grains grew faster than other grains at the initial stage of annealing. Further annealing led to the dissipation of Cl, resulting in the shrinkage of <001> grains while <110> grains continuously grew, as analyzed by x-ray rocking curve and diffraction. As a result of reduced grain boundaries and enhanced <110> texture, the trap density of perovskite solar cells diminished by ~10% by incorporating MACl in the precursor, resulting in a fill factor more than 80%.
Highlights
An organic-inorganic hybrid perovskite solar cell has emerged as a most promising photovoltaic among next-generation solar cells owing to their proper optical/electronic properties resulting in the photovoltaic efficiency over 23%, with low loss of open-circuit voltage and low-temperature processability reducing the production cost[1,2,3,4,5,6]
Intermediate phases containing Cl, which eventually transform into method of incorporating Cl into CH3NH3PbI3 (MAPbI3) upon thermal annealing, slow down the reaction kinetics contributing to the enhanced coverage[7,23,24]
In the case of perovskite with stoichiometric precursor, intensities of all of the perovskite peaks are enhanced with annealing, and minor PbI2 peak appears at 12.7° after annealing for 180 s indicating partial thermal decomposition of the perovskite, as shown in the log-scale diffraction patterns of Fig. 1(a)
Summary
Received: 12 October 2018 Accepted: 5 March 2019 Published: xx xx xxxx of Solar Cell. We synthesized MAPbI3(Cl) perovskite films by using excess MACl-containing precursors, which exhibited approximately an order of magnitude larger grain size with higher -preferred orientation compared with that from stoichiometric precursors. As a result of reduced grain boundaries and enhanced texture, the trap density of perovskite solar cells diminished by ~10% by incorporating MACl in the precursor, resulting in a fill factor more than 80%. Apparent correlation between the changes in preferred orientation, distribution of grain size, and the amount of remaining Cl in the films is observed elucidating the effect of Cl on the formation processes. Due to the improved texture and diminished deep trap density, the fill factor of solar cells reached over 80%
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