The passivation of defects at perovskite grain boundaries (GB) is crucial in achieving highly efficient and stable perovskite solar cells. Unlike the widely used additive passivation method where a mixture of additives and perovskite precursor is used for preparing perovskite films, we herein developed a new defect post-healing method via dip-coating trioctylphosphine oxide (TOPO) ligands on pre-fabricated carbon-based mesoscopic perovskite solar cells (MPSCs). Since perovskites have formed before post-healing, TOPO ligands are selectively adsorbed onto the exposed perovskite surface and hence have little influence on charge extraction of interfaces. The defects are post-healed via O atoms in PO bonds coordinated to halide-deficient sites, leading to an enhancement of the power conversion efficiency (PCE) from 11.0% to 12.8%. Moreover, due to the three hydrophobic long chain alkyls in TOPO, the humidity stability of the device has also been improved simultaneously.

Luminescent solar concentrators are translucent photovoltaic modules potentially used for building window. To store the energy generated by them, a separate energy storage module and voltage regulator module are required, but it is clear that this pairing is unwieldy for application. To address this problem, we propose a “face-to-face” tandem integration of luminescent solar concentrators and electrochromic supercapacitors. In this case, the separated energy storage module and voltage regulator module are not required, since the electric energy produced by concentrators under sunlight can be directly stored by the supercapacitors with matched voltage window. The charged energy storage module can be used to supply low-power devices. Moreover, electrochromic supercapacitors exhibit adjustable average visible transmission under different energy storage state, making the integrated device interesting for self-powered electrochromic smart windows or display devices. As an example, a self-powered information instruction display is prepared, and text messages could be clearly and rapidly displayed in a controllable manner. The integrated device capable of photovoltaic conversion, energy storage, and electrochromism is a promising alternative for smart windows.

Improvement in the synthesis of copper halide perovskites is fundamental in applications of different areas including LEDs, energy harvesting, detection, etc. , and further highlights the direction for future research.