Polystyrene enhanced crystallization of perovskites towards high performance solar cells

Hydrophobic-Hydrophilic Block Copolymer Mediated Tuning of Halide Perovskite Photosensitive Device Stability and Efficiency

The polymer additive strategy provides a facile and cost-effective way for passivating defects and trap sites at the grain boundaries and interfaces and acting as a barrier against the external degradation factors in perovskite-based devices. However, limited literature exists discussing the integration of hydrophobic and hydrophilic polymer additives in the form of a copolymer within the perovskite films. The inherent difference in the chemical structure of these polymers and their interaction with perovskite components and the environment leads to critical differences in the respective polymer-perovskite films. The current work utilizes both homopolymer and copolymer strategies to understand the effect of polystyrene (PS) and polyethylene glycol (PEG), two common commodity polymers, over the physicochemical and electro-optical properties of the as-fabricated devices and the distribution of polymer chains across the depth of perovskite films. The hydrophobic PS integrated perovskite devices PS-MAPbI₃, 36 PS-b-1.4-PEG-MAPbI₃, and 21.5 PS-b-20-PEG-MAPbI₃ outperform hydrophilic PEG-MAPbI₃ and pristine MAPbI₃ devices and exhibit higher photocurrent, lower dark currents, and greater stability. A critical difference is also observed in the stability of devices, where rapid decay of performance is observed in the pristine MAPbI₃ films. The deterioration in performance is highly limited for hydrophobic polymer-MAPbI₃ films as they maintain 80% of their initial performance.

Preparation of Micron-sized Methylamine-PbCl3 perovskite grains by controlling phase transition engineering for selective Ultraviolet-harvesting transparent photovoltaics

Selective ultraviolet-harvesting transparent perovskite solar cells (T-PSCs) have attracted great interest because of their high transmittance and unique photovoltaic properties, especially in the fields of smart windows for power generation and building glass. However, owing to the unsatisfactory solubility of PbCl₂ in most conventional solvents, preparing transparent methylammonium lead chloride (MAPbCl₃) films with high quality and sufficient thickness by conventional methods poses a substantial challenge for their application deployment in T-PSCs. In this work, two novel strategies based on an ion-exchange procedure for controlling phase transition engineering (CPTE) are proposed. For CPTE-2, an optimized cubic phase MAPbCl₃ film with a large grain size and high full coverage is prepared by transforming the tetragonal phase MAPbI₃ precursor into the cubic phase MAPbCl₃. Establishing relevant models based on crystal parameters investigates the formation mechanism of this high-quality MAPbCl₃ film. Accordingly, the resultant T-PSCs exhibit remarkable film quality and micron-sized grains and reach an optimum efficiency of 0.33% (J_SC = 0.66 mA cm^-2, V_OC = 1.14 V, and FF = 43.72%).

Nanoscale Architecture of Polymer-Organolead Halide Perovskite Films and the Effect of Polymer Chain Mobility on Device Performance

The integration of polymer chains with organolead halide perovskite (MAPbI₃) films, leading to enhanced stability and electro-optical performance, is critically affected by the molecular weight of chains. The molecular weight determines the mobility and volume of the chains, which affects the crystallization kinetics and, hence, perovskite grain size. The insulating nature of the chains is another critical factor that affects both ion migration and conduction of electronic charge. The combined effect of these factors leads to optimal performance with the use of medium-length chains. A simple model integrating the two effects accurately fits the response of the polymer-perovskite composite. Further characterization results show that the polymer-perovskite films have a three-layer architecture consisting of nanoscale polymer-rich top and bottom layers. These combined results show that the optimization of performance in polymer-perovskite devices depends critically on the size of the chains due to their multiple effects on the perovskite matrix.