Vertically oriented low-dimensional perovskites for high-efficiency wide band gap perovskite solar cells

             This Paper of the Day discusses the development of vertically oriented low-dimensional perovskites (LDPs) with a wide band gap of around 2 eV, which can be effectively integrated into high-efficiency perovskite solar cells (PSCs). The key findings are the addition of chlorine (Cl) to the precursor solution induces a switch in the crystal orientation of the LDP thin films, from a horizontal to a vertical alignment of the inorganic layers. This vertical alignment is critical for efficient charge transport and extraction in the solar cell device Computational modelling reveals that Cl partially substitutes iodide (I) in the equatorial position of the perovskite octahedra, creating a strain that leads to the elongation of the unit cell along the vertical axis and triggers the vertical crystallization. When integrated into a solar cell device, the vertical orientation of the LDP active layer is preserved, enabling a champion power conversion efficiency of 9.4% - the highest reported for a 2-eV band gap LDP-based PSC. The vertically oriented LDP solar cells also demonstrate excellent operational stability, with 80% of the initial efficiency retained after 150 hours under continuous illumination. The concept is further validated in semi-transparent devices, showing high average visible transmittance of 31%, highlighting the potential of low-n LDPs for building-integrated photovoltaics and indoor energy harvesting applications.