Controllable Grain Morphology of Perovskite Absorber Film by Molecular Self-Assembly toward Efficient Solar Cell Exceeding 17%

摘要

The highly developed crystallization process with respect to perovskite thin films is favorable for efficient solar cells. Here, an innovative intermolecular self-assembly approach was employed to retard the crystallization of PbI_2 in dimethylformamide (DMF) by additional solvent of dimethyl sulfoxide (DMSO), which was proved to be capable of coordinating with Pbl2 by coordinate covalent bond. The obtained PbI_2(DMSO)_x (0 ≤ x ≤ 1.86) complexes tend to be closely packed by means of intermolecular self-assembly. Afterward, an intramolecular exchange of DMSO with CH_3NH_3I (MAI) enabled the complexes to deform their shape and finally to reorganize to be an ultraflat and dense thin film of CH_3NH_3PbI_3. The controllable grain morphology of perovskite thin film allows obtaining a power conversion efficiency (PCE) above 17% and a stabilized power output above 16% within 240 s by controlling DMSO species in the complex-precursor system (CPS). The present study gives a reproductive and facile strategy toward high quality of perovskite thin films and efficient solar cells.