Design and Efficiency of Perovskite Solar Cells

Structural and Manufacturing Features

Solar panels and batteries are made from various materials, including carefully grown silicon with specific doping properties and perovskites. The technology for producing and applying perovskite layers is significantly simpler compared to their silicon counterparts, allowing the process to be reduced to spreading the material over a surface and drying it. Lead halide-based perovskites can efficiently convert solar energy into electricity even in the presence of numerous impurities and defects, demonstrating efficiency levels comparable to industry standards.

Operating Mechanism and the Role of Defects

Unlike silicon solar cells, whose efficiency depends on the perfection of their internal structure, perovskites utilize a natural network of structural defects. These defects do not act as traps for charge carriers but instead form unique pathways along which charges can travel over considerable distances. In ideal perovskite samples, electrons and holes quickly recombine, but in larger samples with a developed defect network, they remain separated long enough to generate useful current.

Experimental Studies

Physicists from the Institute of Science and Technology Austria (ISTA) conducted research aimed at explaining the high efficiency of perovskites. During experiments using nonlinear optical methods, electrons and holes were introduced into the material, and current was detected even without an applied voltage. This confirmed the presence of internal factors that facilitate charge separation and transport.

In the structure of perovskites, slight atomic displacements create domains of electric polarization, separated by domain walls—regions where the direction of the electric field changes sharply. Strong electric fields and mechanical deformations arise at these walls, allowing charges to remain separated and move along the branched network of domain boundaries.

Structural Visualization

To confirm the hypothesis about the role of domain walls, a method of electrochemical staining was developed, in which silver ions penetrate the material and accumulate at the domain walls. After electrochemical conversion of the ions into metallic silver, these structures become visible throughout the material's volume.

Significance for Solar Energy

If an electron-hole pair forms near a domain wall, the local electric field separates the charge carriers to opposite sides of the boundary, preventing their rapid recombination. This allows charges to move along the domain walls for extended periods and over long distances, contributing to the high efficiency of solar energy conversion.

The research data confirm the existence of branched pathways for charge transport in perovskites, making these materials promising for further study and modification of their properties for use in electronics.