Solvent-Antisolvent Ambient Processed Large Grain Size Perovskite Thin Films for High-Performance Solar Cells

Abstract

In recent years, hybrid organic-inorganic halide perovskites have been widely studied for the low-cost fabrication of a wide range of optoelectronic devices, including impressive perovskite-based solar cells. Amongst the key factors influencing the performance of these devices, recent efforts have focused on tailoring the granularity and microstructure of the perovskite films. Albeit, a cost-effective technique allowing to carefully control their microstructure in ambient environmental conditions has not been realized. We report on a solvent-antisolvent ambient processed CH3NH3PbI3−xClx based thin films using a simple and robust solvent engineering technique to achieve large grains (>5 µm) having excellent crystalline quality and surface coverage with very low pinhole density. Using optimized treatment (75% chlorobenzene and 25% ethanol), we achieve highly-compact perovskite films with 99.97% surface coverage to produce solar cells with power conversion efficiencies (PCEs) up-to 14.0%. In these planar solar cells, we find that the density and size of the pinholes are the dominant factors that affect their overall performances. This work provides a promising solvent treatment technique in ambient conditions and paves the way for further optimization of large area thin films and high performance perovskite solar cells.

A Nontoxic Bifunctional (Anti)Solvent as Digestive‐Ripening Agent for High‐Performance Perovskite Solar Cells

“…At the same time, part of organic components (e.g., methylammonium iodide (MAI)) in perovskite precursors tends to evaporate rather than form a perovskite phase during annealing procedure, due to the high volatility and instability of MAI, thus the perovskite evolves into PbI 2 and loses its excellent photovoltaic properties over time 28–32. This tangled problem can be partially mitigated by using mixed‐(anti)solvent system to regulate perovskite films growth dynamic, such as CB/isopropyl alcohol,33 CB/ethanol,34 CB/acetonitrile,35 and EA/hexane 36. These studies found that the percentage and solubility of additive solvents in mixed‐(anti)solvent system contribute to manipulate the morphology of the perovskite active layers 34.…”

“…This tangled problem can be partially mitigated by using mixed‐(anti)solvent system to regulate perovskite films growth dynamic, such as CB/isopropyl alcohol,33 CB/ethanol,34 CB/acetonitrile,35 and EA/hexane 36. These studies found that the percentage and solubility of additive solvents in mixed‐(anti)solvent system contribute to manipulate the morphology of the perovskite active layers 34. However, it is a challenge to optimize the formulation of mixed‐(anti)solvent systems which greatly increases the time cost.…”

In Situ 2D Perovskite Formation and the Impact of the 2D/3D Structures on Performance and Stability of Perovskite Solar Cells

“…However, the grains in the modified films are larger and with the same dimension of the thickness. We believe that the chloroform solvent promoted a slightly superficial dissolution of the perovskite film, allowing the surfactant to reorganize and form the 2D structures . This is an indication of a total penetration of the surfactant solution into the perovskite film.…”

Crystalline Clear or Not: Beneficial and Harmful Effects of Water in Perovskite Solar Cells

“…Through this method, they similarly observed as previously, larger perovskite crystallites at higher %RH with reduced grain boundaries and hysteretic behaviour that they attributed to a decrease in traps states. [52] In their case, (Figure 4c) a combination of ethanol (EtOH) and chlorobenzene (CB) in various volumetric proportions is revealed as the crucial protagonist avoiding pin-holes and obtaining controllable size of perovskite grains, improving as well the photovoltaic parameters to achieve PCE up to 14 % in a planar configuration. [51] In their work, methanol is used as an additive onto the diethylether antisolvent to remove the residual water occluded in the perovskite material during first steps of crystallization (Figure 4b).…”