Aligned and Graded Type‐II Ruddlesden–Popper Perovskite Films for Efficient Solar Cells

Abstract

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

Highly Efficient Guanidinium‐Based Quasi 2D Perovskite Solar Cells via a Two‐Step Post‐Treatment Process

“…These broad additional peaks represent a series of ( 00l ) reflection of (GAMA)MA n −1 Pb n I 3 n +1 with different n values . Charge carrier transport along the vertical direction will be hindered by the 2D spacer layers, and thus crystal growth in the (00l) direction should therefore be avoided. Interestingly, the broad peaks at around 12° and 16° almost disappear upon the application of the GASCN post‐treatment method, indicating that the orientation within the GASCN treated films is improved.…”

Μethylammonium Chloride: A Key Additive for Highly Efficient, Stable, and Up‐Scalable Perovskite Solar Cells

“…These perovskites can be structurally derived from their 3D counterparts with alternating long, hydrophobic organic ammonium layers and perovskite layers, giving the general formula of (RNH 3 ) 2 A nÀ1 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. [89] Even more importantly, a novel 2D RPP with a low n value of 3 was fabricated using 2-thiophenemethylammonium (ThMA + ) as a spacer cation and MACl-additive enhanced crystallization. [87] For instance, Chen et al have incorporated MACl into (PEA) 2 Pb 6 I 14 perovskite.…”

Enhancing the Performance of the Half Tin and Half Lead Perovskite Solar Cells by Suppression of the Bulk and Interfacial Charge Recombination

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14] However, the toxicity of lead causes big concerns about their large-scale application. So far, lead halide perovskites have been studied mostly in single junction solar cells, and only after about eight years of optimization of the film morphology and device structure they achieved record power conversion efficiency (PCE) approaching 23.0%.…”