Correlation between Electronic Defect States Distribution and Device Performance of Perovskite Solar Cells

Abstract

In the present study, random current fluctuations measured at different temperatures and for different illumination levels are used to understand the charge carrier kinetics in methylammonium lead iodide CH3NH3PbI3‐based perovskite solar cells. A model, combining trapping/detrapping, recombination mechanisms, and electron–phonon scattering, is formulated evidencing how the presence of shallow and deeper band tail states influences the solar cell recombination losses. At low temperatures, the observed cascade capture process indicates that the trapping of the charge carriers by shallow defects is phonon assisted directly followed by their recombination. By increasing the temperature, a phase modification of the CH3NH3PbI3 absorber layer occurs and for temperatures above the phase transition at about 160 K the capture of the charge carrier takes place in two steps. The electron is first captured by a shallow defect and then it can be either emitted or thermalize down to a deeper band tail state and recombines subsequently. This result reveals that in perovskite solar cells the recombination kinetics is strongly influenced by the electron–phonon interactions. A clear correlation between the morphological structure of the perovskite grains, the energy disorder of the defect states, and the device performance is demonstrated.

Insights Into the Microscopic and Degradation Processes in Hybrid Perovskite Solar Cells Using Noise Spectroscopy

“…A combination of various response characteristics along with noise studies is needed to interpret the degradation mechanism at different stages. An example of such an approach has been taken up by Landi et al where the measured defect state energetics are correlated to the device performance. In the present case, we follow the changes induced by the evolving defects with degradation.…”

Tin Halide Perovskites: Progress and Challenges

“…Such structural changes can, improve the carrier lifetime and reduce background dopant density by altering the energy level alignment between Sn vacancies (V Sn ) and the valence band maximum (VBM). Evidently, crystal structure, hole doping, disorder and carrier lifetime are intrinsically linked in perovskite materials and they depend on structural changes at phase transition . Also, exploiting the excess energy from charges occupying higher energy states in the such materials could further improve their efficiency.…”

Rationalizing the Molecular Design of Hole‐Selective Contacts to Improve Charge Extraction in Perovskite Solar Cells

“…[1] Perovskite solar cells (PSCs) in particular have shown great potential as the alternative, highly efficient photovoltaics (PVs) to the well-established PV technology. [4][5][6] Moreover, monolithic films can be easily formed between the electron selective contact (ESC) and the hole selective contact (HSC). [4][5][6] Moreover, monolithic films can be easily formed between the electron selective contact (ESC) and the hole selective contact (HSC).…”