promise for low-cost solution processability. [1][2][3][4] Perovskite solar cells have experienced tremendous development in the past few years with power conversion efficiency (PCE) rapidly increased to over 20%. [5,6] Besides efficiency, another critical factor for practical application of perovskite solar cells is stability.Recently, Ruddlesden-Popper perovskites (RPPs) have been reported to have promising stability. [7][8][9] The RPPs can be structurally derived from their 3D counterparts with alternating organic ammonium layers and perovskite layers, giving the general formula of (RNH 3 ) 2 A n−1 M n X 3n+1 , where n represents the number of perovskite layers, RNH 3 is the organic spacer, and the A (small cation), M (divalent metal cation), and X (halide anion) form the perovskite framework. [10,11] The superior stability of RPPs can be attributed to the hydrophobic property of the organic spacer, which inhibits water molecules from penetrating and attacking the inorganic layers.Previous studies reported that RPPs exhibit enhanced stability but at the cost of reduced efficiency due to lower Recently, Ruddlesden-Popper perovskites (RPPs) have attracted increasing interests due to their promising stability. However, the efficiency of solar cells based on RPPs is much lower than that based on 3D perovskites, mainly attributed to their poor charge transport. Herein, a simple yet universal method for controlling the quality of RPP films by a synergistic effect of two additives in the precursor solution is presented. RPP films achieved by this method show (a) high quality with uniform morphology, enhanced crystallinity, and reduced density of sub-bandgap states, (b) vertically oriented perovskite frameworks that facilitate efficient charge transport, and (c) type-II band alignment that favors self-driven charge separation. Consequently, a hysteresis-free RPP solar cell with a power conversion efficiency exceeding 12%, which is much higher than that of the control device (1.5%), is achieved. The findings will spur new developments in the fabrication of high-quality, aligned, and graded RPP films essential for realizing efficient and stable perovskite solar cells. Solar CellsOrganic-inorganic halide perovskites, such as MAPbI 3 (MA = CH 3 NH 3 ), FAPbI 3 (FA = CH(NH 2 ) 2 ), and their mixed cation analogues, have emerged as promising light absorbers for solar cells due to their superior photophysical properties and

A high-performance hybrid white organic light-emitting device (WOLED) is demonstrated based on an efficient novel thermally activated delayed fluorescence (TADF) blue exciplex system. This device shows a low turn-on voltage of 2.5 V and maximum forward-viewing external quantum efficiency of 25.5%, which opens a new avenue for achieving high-performance hybrid WOLEDs with simple structures.

Interfacial reactions between the perovskite emitters and the interlayers are detrimental to the operational stability of the perovskite light-emitting diodes. Incorporating dicarboxylic acids into the precursor efficiently eliminates reactive organic ingredients in the perovskite emitters through an in situ amidation process, which is catalyzed by the alkaline zinc oxide substrate underneath. The formed amides improve the stability of the perovskite emitters and the charge injection contacts, ensuing notably improved operational stability of the resulting perovskite light-emitting diodes.