Shallow defects and variable photoluminescence decay times up to 280 µs in triple-cation perovskites.

Quantifying recombination in halide perovskites is a crucial prerequisite to control and improve the performance of perovskite-based solar cells. While both steady-state and transient photoluminescence are frequently used to assess recombination in perovskite absorbers, quantitative analyses within a consistent model are seldom reported. We use transient photoluminescence measurements with a large dynamic range of more than ten orders of magnitude on triple-cation perovskite films showing long-lived photoluminescence transients featuring continuously changing decay times that range from tens of nanoseconds to hundreds of microseconds.

Understanding the Thickness and Light-Intensity Dependent Performance of Green-Solvent Processed Organic Solar Cells.

For indoor light harvesting, the adjustable band gap of molecular semiconductors is a significant advantage relative to many inorganic photovoltaic technologies. However, several challenges have to be overcome that include processability in nonhalogenated solvents, sufficiently high thicknesses (>250 nm) and high efficiencies at illuminances typically found in indoor environments. Here, we report on the development and application of new methods to quantify and identify performance losses based on thickness- and intensity-dependent current density-voltage measurements.

Homogenizing out-of-plane cation composition in perovskite solar cells.

Perovskite solar cells with the formula FACsPbI, where FA is formamidinium, provide an attractive option for integrating high efficiency, durable stability and compatibility with scaled-up fabrication. Despite the incorporation of Cs cations, which could potentially enable a perfect perovskite lattice, the compositional inhomogeneity caused by A-site cation segregation is likely to be detrimental to the photovoltaic performance of the solar cells. Here we visualized the out-of-plane compositional inhomogeneity along the vertical direction across perovskite films and identified the underlying reasons for the inhomogeneity and its potential impact for devices.

Quantifying Charge Extraction and Recombination Using the Rise and Decay of the Transient Photovoltage of Perovskite Solar Cells.

The extraction of photogenerated charge carriers and the generation of a photovoltage belong to the fundamental functionalities of any solar cell. These processes happen not instantaneously but rather come with finite time constants, e.g.