The defects in the light-harvesting perovskite absorber layer play a key role in limiting power conversion efficiencies (PCEs) and long-term stability of lead halide perovskite solar cells (PSCs). Although organic ammonium halides have been used for defect passivation in high-performance PSCs, the stability issue is still a challenge. Herein, we develop a novel material of pyridine-carbazole (Py-Cz) to passivate defects via coordination bonding. With this passivation, the photoluminescence intensity of perovskite films was increased. In addition, the formation of under-coordinated Pb2+ defects in perovskite films was reduced significantly, enabling high-performance and long-term stable PSCs. Three different sets of PSCs were constructed, namely, without passivation, with phenethylammonium iodide (PEAI) (commonly used for passivation), and with Py-Cz passivation. Remarkably, the PSCs fabricated using the Py-Cz passivation not only achieved PCEs of over 20% but also retained 85% of their initial performances over more than 5000 h. In contrast, the PSCs without or with PEAI passivation degraded quickly during the long-term operational stability test under light illumination. This method opens up a new opportunity to develop highly efficient and operationally stable PSCs.

In inverted architectures of perovskite solar cells (PSCs), poly­(3,4-ethylenedioxythiophene):poly­(styrenesulfonate) (PEDOT:PSS) has been widely used as the hole transport layer (HTL). An issue occurring in such PSCs is that the hole transport level of PEDOT:PSS shifts upward since methylammonium iodide (MAI) used for the perovskite structure organization interacts with the underlying PEDOT:PSS HTL as a reducing agent, which impedes hole extraction and therefore lowers the performance of PSCs. To overcome this issue, we demonstrate a way of adding tetraethoxysilane (TEOS) into a water-based PEDOT:PSS solution. The HTL spin-coated from the solution contains PEDOT:PSS, which is blended with siloxanes because the polymerization of TEOS takes place via the hydrolysis reaction. This siloxane blending suppresses the MAI-induced reducing reaction and upward energy-level shift of PEDOT:PSS. Using the siloxane-blended PEDOT:PSS HTL in PSCs leads a ∼1.3-fold increase in power conversion efficiencies of iodide-based PSCs from the original ∼10.58% to ∼13.65%.

Metal halide perovskite light‐emitting diodes (LEDs) are promising for future display applications because of their excellent advantages, such as high external quantum efficiency, emission color tunability, and high emission color purity. Although solution processing widely used for perovskite film fabrication is an additional advantage, there are cases in which fabricating a perovskite‐emitting layer with spin‐coating results in the dissolution of an underlying organic hole transport layer (HTL). As a result, since a perovskite layer comes into partial contact with an indium tin oxide (ITO) anode layer, excited states formed in a perovskite‐emitting layer are quenched by charge transfer to ITO. In this study, it is shown that adding tetraethyl orthosilicate (TEOS) into a HTL material of poly(N‐vinylcarbazole) (PVCz) is an effective method used to overcome this issue. Upon heating, the hydrolysis reaction of TEOS molecules takes place in PVCz films to form a siloxane network, which makes PVCz films insoluble and, therefore, alleviates the excited‐state quenching. It is demonstrated that using the siloxane‐blended PVCz HTL increases external quantum efficiencies of perovskite LEDs to 15.4 ± 0.3% from the original 10.4 ± 0.3% by about 1.5 times.