The stability of CsGeX (X = I, Br, Cl) selectively tuned by the crystal structures and halide ions as inferred from the calculated phonon spectrum.

In spite of the considerable advancements achieved in enhancing the power conversion efficiency (PCE) of lead-based all-inorganic perovskite solar cells, there persists a need for materials that are both more stable and environmentally friendly. This investigation systematically explores the structural and thermodynamic stability, and electronic properties of Ge-based all-inorganic perovskite CsGeX (X = Cl, Br, I) in two space groups, 3̄ and 3, utilizing first-principles calculations. Introducing the novel concept of the "imaginary frequency coefficient" alongside the tolerance factor and stabilizing the chemical potential window, we collectively characterize the stability of CsGeX based on the phonon spectrum and phonon density of states calculations.

Buried Interface Modification Toward Efficient CsPbIBr Based Monolithic Perovskite/Organic Tandem Solar Cells.

Wide-bandgap perovskite sub-cells (WPSCs), one of the most crucial components of perovskite-based tandem solar cells (PTSCs), play a critical role in determining the performance of tandem devices. However, confined by the compromised crystallization properties of wide-bandgap perovskites, WPSCs exhibit significantly lower efficiency than their theoretical limit. In particular, for n-i-p structured all-inorganic WPSCs (AIWPSCs), severe nonradiative recombination due to the buried interface defects severely decreases the photovoltaic performance.