High Efficiency Quasi‐2D Ruddlesden–Popper Perovskite Solar Cells

Abstract

Quasi‐2D Ruddlesden–Popper perovskites (RPPs) are promising candidates for stable and efficient solar cells. Even though photovoltaic devices based on these materials are still lagging behind traditional 3D perovskites, they have experienced a dramatic increase in power‐conversion efficiency, recently reaching >20%. As knowledge develops, the toolbox of RPP researchers is steadily growing in terms of organic spacers, additives, and characterization methods. This review aims to describe the use of such a toolbox to achieve high efficiency solar cells. The use of additives, functionalized spacers, and novel fabrication techniques are explored to control morphology, crystallinity, interlayer interaction, and phase distribution. Moreover, methods to achieve the coveted phase purity in RPPs and its implications on both single‐ and multi‐junction solar cells are discussed. By describing successful cases of high efficiency solar cells combined with in‐depth knowledge of material properties, it is shown that there are still several open research questions that need exploring to further develop this fascinating class of perovskites.

High‐Quality Lead Acetate–Based Ruddlesden–Popper Perovskite Films for Efficient Solar Cells

“…Lastly, to examine the general applicability of our method, we extend PbAc 2 ‐based precursor to fabricate BA‐based RPP of (BA) 2 (MA) 3 Pb 4 I 13 , which is also widely investigated for solar cells. [ 26 ] As shown in Figure S16, Supporting Information, the absorption spectrum of the BA‐based RPP film shows several excitonic absorption peaks from small‐ n phases, suggesting the formation of mixed RPP phases. Strong diffraction signals at 2 θ = 14.2° and 28.5° can be also observed in the XRD pattern, indicating high crystallinity and vertical crystal orientation.…”

“…[24] Since the first reported RPP solar cells in 2014, [25] various efforts have been employed to manipulate the crystal growth orientation including hot-casting, solvent engineering, composition engineering, and additives. [26,27] Consequently, the RPP solar cells have recently undergone a rapid increase in PCE to over 21% with improved stability, suggesting their great potential for the scalable industry. [28] Recently, nonhalide lead sources have attracted increasing attention in 3D perovskites due to their potential for improving film quality and simple fabrication process.…”

Humidity‐Insensitive, Large‐Area‐Applicable, Hot‐Air‐Assisted Ambient Fabrication of 2D Perovskite Solar Cells

“…[6,7] Tremendous efforts have been devoted to prepare the optimal LP films for solar cells. [8][9][10][11][12][13] The crystal orientation is one of the key factors that determine the quality of LP films due the gas-liquid interface which functionalizes as a template for the nucleation and inward growth of LP crystals during film drying. [28][29][30] A delicate balance between the rates of nucleation and crystal growth should be reached to attain high-quality LP films.…”

Green Solvent Polishing Enables Highly Efficient Quasi-2D Perovskite Solar Cells

“…The OIHP solar cells have reached an impressive power conversion efficiency (PCE) over 25% . However, the bottleneck for the perovskite solar cells (PSCs) is the vulnerability to moisture, heat, and oxygen. − In recent years, quasi-2D perovskites, acting as alternatives to the traditional 3D counterparts, have shown great potential in resisting moisture and oxygen. − Besides the superior stability, the quasi-2D perovskites present flexible choices of the bulky cations and less restriction of the tolerance factor, enabling diverse structures and tunable physical properties. , Basically, quasi-2D perovskites are formed by inserting bulk organic cations into the Pb–I frameworks. For the most common Ruddlesden–Popper quasi-2D perovskites, the generic chemical formula is A’ 2 A n– 1 M n X 3 n +1 where the A’ is the bulky organic cation (butylamine ion (BA + ), phenethylammonium ion (PEA + ), etc.)…”

“…7−9 Besides the superior stability, the quasi-2D perovskites present flexible choices of the bulky cations and less restriction of the tolerance factor, enabling diverse structures and tunable physical properties. 10,11 Basically, quasi-2D perovskites are formed by inserting bulk organic cations into the Pb−I frameworks. For the most common Ruddlesden−Popper quasi-2D perovskites, the generic chemical formula is A' 2 A n−1 M n X 3n+1 where the A' is the bulky organic cation (butylamine ion (BA + ), phenethylammonium ion (PEA + ), etc.)…”