Controlled crystallization of CH3NH3PbI3 films for perovskite solar cells by various PbI2(X) complexes

Abstract

a b s t r a c tLead halide complexes are efficient precursors to obtain high quality perovskite films and high performance solar cells. However, how the lead halide complex affects the crystallization kinetics and thus the film quality of perovskite has not been systematically studied. Herein, two PbI 2 (X) complexes with different coordination strength of ligand X in complexation with PbI 2 (PbI 2 (DMF) and PbI 2 (DMSO)) are synthesized. The correlation between the morphology, evolution of the perovskite formation, defects state, carrier lifetime and the subsequent photovoltaic performance are investigated in details via a twostep coating method with various PbI 2 (X) complexes. We find that PbI 2 (DMSO) derived perovskite film shows larger grains and vertically oriented grain boundaries as well as enhanced photoluminescence intensity and longer carrier lifetime. As a result, highly efficient inverted planar perovskite solar cells with a power conversion efficiency up to 17.0% are achieved from PbI 2 (DMSO) complex under 1 sun illumination. This research could open up a new pathway to further improve the performance of perovskite solar cells through the control of perovskite crystallization kinetics by choosing proper PbI 2 (X) complex precursors.

Capturing the Sun: A Review of the Challenges and Perspectives of Perovskite Solar Cells

“…As a result, crystallization becomes more controllable, which leads to uniform crystals, often with increased sizes. [23,24,33,34] Chemically, this complex can be described as the solvent molecules donating a free electron pair to the Pb 2+ ions. These so-called Lewis adducts are comparable to the lead-halide cage in the final perovskite structure.…”

The Impact of a Dynamic Two‐Step Solution Process on Film Formation of Cs0.15(MA0.7FA0.3)0.85PbI3 Perovskite and Solar Cell Performance

“…Other work has also reported the deposition of PbI 2 ‐complex to promote an intermediate phase before the second conversion step with the idea of controlling perovskite crystallization. Among those applications, Fu et al compared the PbI 2 (DMF) and PbI 2 (dimethyl sulfoxide (DMSO)) complex precursors and found that perovskite film from PbI 2 (DMSO) shows reduced defects with higher quality . Cao et al claimed that when PbI 2 precipitates from DMF solution, the “Lewis acid–base adducts” of PbI 2 ‐ x DMF complex allows for the expansion of the lattice of PbI 2 , for MAI diffusion during the second immersion step .…”

A Review on Halide Perovskite Film Formation by Sequential Solution Processing for Solar Cell Applications

“…c) Top‐surface SEM images of film prepared by pristine PbI 2 (left), PbI 2 (DMF) complex (middle), and PbI 2 (DMSO) complex (right). Reproduced with permission . Copyright 2016, Elsevier.…”

“…d) Absorbance with steady‐state PL (left) and carrier lifetime (right) for perovskite prepared by pristine PbI 2 (black), PbI 2 (DMF) (red), and PbI 2 (DMSO) (blue). Reproduced with permission . Copyright 2016, Elsevier.…”