Two-dimensional Perovskite Solar Cells Research Articles

Boosting MA-based two-dimensional Ruddlesden-Popper perovskite solar cells by incorporating a binary spacer

Two-dimensional Ruddlesden-Popper (2DRP) perovskite exhibits excellent stability in perovskite solar cells (PSCs) due to introducing hydrophobic long-chain organic spacers. However, the poor charge transporting property of bulky organic cation spacers limits the performance of 2DRP PSCs. Inspired by the A-site cation alloying strategy in 3D perovskites, 2DRP perovskites with a binary spacer can promote charge transporting compared to the unary spacer counterparts. Herein, the superior MA-based 2DRP perovskite films with a binary spacer, including 3-guanidinopropanoic acid (GPA) and 4-fluorophenethylamine (FPEA) are realized. These films (GPA0.85FPEA0.15)2MA4Pb5I16 show good morphology, large grain size, decreased trap state density, and preferential orientation of the as-prepared film. Accordingly, the present 2DRP-based PSC with the binary spacer achieves a remarkable efficiency of 18.37% with a VOC of 1.15 V, a JSC of 20.13 mA cm−2, and an FF of 79.23%. To our knowledge, the PCE value should be the highest for binary spacer MA-based 2DRP (n ≤ 5) PSCs to date. Importantly, owing to the hydrophobic fluorine group of FPEA and the enhanced interlayer interaction by FPEA, the unencapsulated 2DRP PSCs based on binary spacers exhibit much excellent humidity stability and thermal stability than the unary spacer counterparts.

Enhanced performance and stability of quasi two-dimensional perovskite solar cells by conductive phosphine oxide

Recently, quasi two-dimensional (quasi-2D) perovskite solar cells (PSCs) have been paid more attentions due to their good stability. While the efficiency of 2D PSCs is lower than that of 3D ones due to their poor charge transport property. Here we introduced a conductive material of 2,7-bis(diphenylphosphoryl)-9,9′-spirobifluorene (SPPO13) into the precursor solution of quasi-2D perovskite GAMA5Pb5I16 (GA = guanidinium, MA = methylammonium) to improve the charge transfer property. The efficiency of the PSCs with SPPO13 is increased to 18.58 % from 16.97 % for the control, which is resulting from the enlarged grain size, increased electrical conductivity, and reduced trap state density induced by the addition of SPPO13. Moreover, the additon of SPPO13 improves the stability of the devices. The normalized PCE of the devices with SPPO13 keeps 90 % of the original value after aging for 30 days in atmosphere. This study provides a novel way to enhance the charge transfer property of 2D perovskite by conductive material for enhanced efficiency and stability of quasi-2D PSCs.

Surface Crystallization Modulation toward Highly-Oriented and Phase-Pure 2D Perovskite Solar Cells.

2D perovskites have shown great potential toward stable and efficient photovoltaic devices. However, the crystal orientation and phase impurity issues of 2D perovskite films originating from the anisotropic crystal structure and specific growth mechanism have demoted their optoelectronic performances. Here, the surface crystallization modulation technique is introduced to fabricate the high-quality 2D perovskite films with both vertical crystal orientation and high phase purity by regulating the crystallization dynamics. The solvent atmosphere condition is instituted during film processing, which promotes the formation of an oriented 2D perovskite layer in stoichiometric composition at the vapor-liquid interface and templates the subsequent film growth. The solar cells based on the optimized 2D perovskite films exhibit a power conversion efficiency of 15.04%, the record for 2D perovskites (with the perovskite slab thickness n ≤ 3 and high phase purity). The solar cells based on the highly-oriented and phase-pure 2D perovskite films also demonstrate excellent thermal and humidity stabilities.

Improved Photovoltaic Performance of Inverted Two-Dimensional Perovskite Solar Cells via a Simple Molecular Bridge on Buried Interface.

NiOx-based two-dimensional perovskite solar cells (2D-PSCs) have the advantages of low fabrication temperature, suitable energy level matching, suppressed hysteresis, and superior stability, while the poor interfacial contacts between NiOx and perovskite layers limit the perovskite film growth and charge transfer. Herein, a simple molecule, urea, was used as a molecular modifier to form bifacial passivation on the buried interface of NiOx/perovskite, resulting in better interfacial contact and efficient bifacial passivation. We demonstrated that efficient bifacial passivation mainly comes from strong interactions between urea and NiOx or perovskite, which make urea a molecular bridge for smoother charge transfer. Moreover, urea can regulate the ratio of Ni3+/Ni2+, therefore boosting the conductivity of NiOx, and adjust the morphology of the NiOx film for better 2D-perovskite crystal growth. Besides, urea also passivates the bifacial defect states of both NiOx and perovskite film, yielding reduced defect density of the perovskite film and superior charge transfer on the buried interface. Consequently, inverted 2D-PSCs with urea modification proved significant improvements in short-circuit current density and fill factor, resulting in improved power conversion efficiency from 14.64 to 16.84% with better stability in air.

Improve the Charge Carrier Transporting in Two-Dimensional Ruddlesden-Popper Perovskite Solar Cells.

Conventional 3D organic-inorganic halide perovskite materials have shown substantial potential in the field of optoelectronics, enabling the power conversation efficiency of solar cells beyond 26%. A key challenge limiting the further commercial application of 3D perovskite solar cells is their inherent instability over outer oxygen, humidity, light, and heat. By contrast, 2D Ruddlesden-Popper (2DRP) perovskites with bulky organic cations can effectively stabilize the inorganic slabs, yielding excellent environmental stability. However, the efficiencies of 2DRP perovskite solar cells are much lower than those of the 3D counterparts due to poor charge carrier transporting property of insulating bulky organic cations. Their inner structural, dielectric, optical, and excitonic properties remain to be primarily studied. In this review, the main reasons for the low efficiency of 2DRP perovskite solar cells are first analyzed. Next, a detailed description of various strategies for improving the charge carrier transporting of 2DRP perovskites is provided, such as bandgap regulation, perovskite crystal phase orientation and distribution, energy level matching, interfacial modification, etc. Finally, a summary is given, and the possible future research directions and methods to achieve high-efficiency and stable 2DRP perovskite solar cells are rationalized.

The Synergistic Effect of Additives for Formamidinium-Based Inverted Dion-Jacobson 2D Perovskite Solar Cells with Enhanced Photovoltaic Performance.

Two-dimensional (2D) perovskite solar cells (PSCs) have attracted rapid growing attention due to their excellent environmental and operational stability. As an important type of 2D perovskite, Dion-Jacobson (DJ) 2D perovskites exhibit better structural integrity and more stable optoelectronic properties than those of Ruddlesden-Popper (RP) ones because of the elimination of weak van der Waals interactions. Random phase distribution, phase impurity, and weak crystallinity, however, can lead to severe nonradiative recombination losses in 2D perovskites and inferior device stability. Herein, formamidinium chloride (FACl) and lead chloride (PbCl2) are selected as additives to fabricate efficient and stable DJ 2D PSCs. The synergistic effect of additives could efficiently induce crystallization and suppress the low-n phase perovskites. The obtained 2D perovskites exhibit extended charge lifetime and enhanced charge transfer. The corresponding PSC device delivers an efficiency of 16.63% with a significantly improved open-circuit voltage (VOC) of 1.18 V and a fill factor (FF) of 81.65% than the control one. This PCE ranks the highest for inverted FA-based 2D DJ PSCs. Moreover, this device has exhibited exceptional long-term stability, which retains more than 95% of the initial efficiencies at about 50% relative humidity for 600 h.

Enhanced Efficiency and Stability of Quasi Two-dimensional Perovskite Solar Cells via Dual Additives

Quasi two-dimensional alternating cation (ACI)-type perovskites have drawn extensive research interest owing to better stability than their 3D counterparts. However, the poor charge-transfer characteristics of quasi two-dimensional perovskite film significantly impact the efficiency and stability of the devices. Herein, we propose a dual additives strategy utilizing urea and methylammonium chloride to manage the growth of (GA)(MA)5Pb5I16 perovskite films. The morphology and photoelectric characteristics manifest that the dual additives not only significantly enlarge the crystal size of the film, but also optimize the distribution of the quantum well thickness. Therefore, the solar cell based on dual additives-treated perovskite film achieves an optimal efficiency of 20.86%, far higher than 17.11% for that without additive. Moreover, the environmental stability of the quasi two-dimensional perovskite solar cells (PSCs) is raised. The unencapsulated PSCs hold 93% of the initial efficiency after being placed under environmental conditions for 1500hours. These results demonstrate that using dual additives is a promising strategy to obtain high-performance PSCs.

Effects of spin-coating speed and precursor concentration in Formamidinium-based layered perovskite films

The effects of precursor solution concentration, spin coating speed and substrate temperature on the crystallinity and optical properties of (BA)2FA2Pb3I10 films are comparatively investigated. On substrates at room temperature or at 110 °C, two-dimensional (2D) perovskite films and solar cells using (BA)2(FA)n−1PbnI3n+1 (n = 3 nominally), with the same molar ratio of components, are fabricated with adding thiourea in the precursor solution. The film fabrication procedure includes two groups: one is with same concentration of 0.25 mol/L (M) based on PbI2 but various spin-casting speeds from 1000 rpm to 6000 rpm; the other is with same spin-coating speed of 4000 rpm but with various concentrations from 0.1 M to 1 M. We find that optical properties and film morphologies (including domain size and crystal orientation) are not sensitive to the spin-casting speed; while the concentration of precursor solution but not substrate temperature had significant effects on the crystalline orientation and domain size, namely, higher concentration of solution results in more preferential out of plane alignment with respect to the substrate and larger crystalline domain size. Device from the 0.25 M solution spin-casted at 4000 rpm on room temperature substrate achieves the best power conversion efficiency (PCE) of 7.5% without J-V hysteresis. Current work demonstrates the highest PCE reported for mixed BA and FA based 2D perovskite solar cells with n < 5, as well as suggests the robustness of (BA)2FA2Pb3I10 as an active material in preparing solar cells.

Highly efficient and stable quasi two-dimensional perovskite solar cells via synergistic effect of dual additives

Recently, quasi two-dimensional (Q-2D) perovskites with alternating cations in the interlayer space (ACI) have attracted more attentions owing to their elevated stability compared with three-dimensional (3D) analogs. While the efficiency of the devices derived from Q-2D perovskites is much smaller than that based on 3D perovskites. Here, we utilized urea and methoxyamine hydrochloride (MOAH) dual additives to acquire high quality Q-2D ACI perovskite GA(MA)5Pb5I16 (GA = guanidinium, MA = methylammonium) films. The efficiency of the perovskite solar cells (PSCs) derived from the Q-2D perovskite films induced by the synergistic effect of urea and MOAH dual additives increases to 20.32% from 17.21% for the devices without additive. This efficiency enhancement could be attributed to the enlarged grain size, improved crystallinity, optimized quantum well thickness distribution, and reduced trap states of the perovskite films. Moreover, the solar cells with dual additives present improved stability. The efficiency of devices with dual additives holds 95% of the original value after storage for 1600 h in ambient air. These results prove that the synergistic effect of urea and MOAH is an effective method to achieve highly efficient and stable Q-2D PSCs.

Research on Preparation and Progress of Two-Dimensional Perovskite Solar Cells

Two-dimensional perovskite solar cells are considered as the most promising new type of solar cells due to their unique advantages such as strong spectral absorption, low cost, adjustable composition, excellent structure, excellent photoelectric characteristics and simple preparation through various processes. This paper will briefly introduce the structure and principle of two-dimensional perovskite solar cells, and introduce the research progress of top electrode materials in detail, including improving the preparation method of metal top electrode materials, repairing and introducing buffer layer and cathode intermediate layer for interface modification. High-performance perovskite solar cells use lead-containing perovskite materials as the light absorbing layer. Even if the device packaging process is perfect, lead-based perovskite materials still have the possibility of causing pollution to the environment, especially when the battery is damaged or the failed solar cells are improperly recycled. Therefore, in this paper, we can obtain high-quality perovskite films by improving the preparation process, solvent engineering and annealing engineering.

Two-dimensional (n=1) ferroelectric film solar cells.

Molecular ferroelectrics that have excellent ferroelectric properties, a low processing temperature, narrow bandgap, and which are lightweight, have shown great potential in the photovoltaic field. However, two-dimensional (2D) perovskite solar cells with high tunability, excellent photo-physical properties and superior long-term stability are limited by poor out-of-plane conductivity from intrinsic multi-quantum-well electronic structures. This work uses 2D molecular ferroelectric film as the absorbing layer to break the limit of multiple quantum wells. Our 2D ferroelectric solar cells achieve the highest open-circuit voltage (1.29V) and the best efficiency (3.71%) among the 2D (n=1) Ruddlesden-Popper perovskite solar cells due to the enhanced out-of-plane charge transport induced by molecular ferroelectrics with a strong saturation polarization, high Curie temperature and multiaxial characteristics. This work aims to break the inefficient out-of-plane charge transport caused by the limit of the multi-quantum-well electronic structure and improve the efficiency of 2D ferroelectric solar cells.

High-performance Ruddlesden–Popper two-dimensional perovskite solar cells using integrated electron transport materials of tin oxide and indacenodithiophene

Perovskite solar cells (PSCs) have been rapidly developed and exhibit comparable power conversion efficiency (PCE) to silicon solar cells.

Progress of Two-dimensional Perovskite Solar Cells Based on Aromatic Organic Spacers

è¿‘å¹´æ¥ï¼Œé’™é’›çŸ¿å¤ªé˜³èƒ½ç”µæ± ï¼ˆPSCs）的效率得到了快速的发展，目前已经获得25.7%çš„è®¤è¯æ•ˆçŽ‡ï¼Œå¯ä¸Žç¡ åŸºå¤ªé˜³èƒ½ç”µæ± ç›¸åª²ç¾Žã€‚ç„¶è€Œï¼ŒPSCsçš„ç¨³å®šæ€§å´è¿œä¸å¦‚ç¡ åŸºå¤ªé˜³èƒ½ç”µæ± ï¼Œè¿™é™åˆ¶äº†PSCs的使用。与此同时，二维（2Dï¼‰æˆ–å‡†äºŒç»´é’™é’›çŸ¿ææ–™å—åˆ°äº†è¶Šæ¥è¶Šå¤šçš„å ³æ³¨ï¼Œä¸»è¦æ˜¯å› ä¸ºå¤§ä½“ç§¯æœ‰æœºé ä½“çš„å¼•å ¥æ˜Žæ˜¾åœ°æ”¹å–„äº†ææ–™çš„ç»“æž„å’ŒçŽ¯å¢ƒç¨³å®šæ€§ã€‚åœ¨2D PSCsé¢†åŸŸï¼Œæœ‰æœºé ä½“ç¦»å­çš„è®¾è®¡å’Œé€‰æ‹©ä¼šç›´æŽ¥å½±å“ææ–™çš„å ‰ç”µæ€§èƒ½å’Œå™¨ä»¶çš„æ•ˆçŽ‡ã€‚ç›®å‰ï¼Œ2D PSCsä¸­æ‰€ä½¿ç”¨çš„æœ‰æœºé ä½“ä¸»è¦åˆ†ä¸ºè„‚è‚ªæ—é ä½“å’ŒèŠ³é¦™æ—é ä½“ã€‚èŠ³é¦™æ—é ä½“ç”±äºŽå ·æœ‰è¾ƒå¤§çš„ä»‹ç”µå¸¸æ•°ã€æ”¹å–„çš„ç”µè·ä¼ è¾“å’Œå¯è°ƒæŽ§çš„ç»„è£ ç»“æž„ç­‰ä¼˜ç‚¹å¾—åˆ°è¶Šæ¥è¶Šå¤šçš„å ³æ³¨ã€‚æœ¬æ–‡ç³»ç»Ÿåœ°æ€»ç»“äº†èŠ³é¦™æ—é ä½“ææ–™å¯¹2Dé’™é’›çŸ¿æ€§èƒ½çš„å½±å“åŠå ¶åœ¨2D PSCs领域的应用。

Super hydrophilic, ultra bubble repellent substrate for pinhole free Dion–Jacobson perovskite solar cells

The progress in efficiency improvements of blade-coated two-dimensional perovskite solar cells (PSCs) lags behind that of spin-coated ones. Pinholes and voids are two important structural defects hiding in blade-coated large-area perovskite films to deteriorate device efficiency and stability. However, the formation of pinholes and voids is still difficult to predict. On substrates with moderate wettability, Dion–Jacobson perovskite films can be blade-coated with good coverage, but we highlight that the formation of nanoscale voids buried at the bottom side of perovskite films can occur frequently, depending critically on the wettability of substrates. It is revealed that super hydrophilic NiOx substrates with contact angle θ &amp;lt; 5° possesses strong bubble repellent property, which thermal dynamically prevents the retraction of precursor solution and plays an important role to suppress the attachment and growth of bubbles on its surface. The probabilities of forming both pinholes and buried voids in perovskite films on super hydrophilic NiOx substrates are one order of magnitude lower than that on hydrophilic PTAA and poly-TPD substrates. The blade-coated (BDA)MA4Pb5I16 films on NiOx substrate offer PSCs with excellent interfacial hole extraction and reduced leakage current, contributing a significant power conversion efficiency improvement from ∼10% to 16.26%.

Synergistic effect of dual anions for efficient and stable quasi 2D perovskite solar cell

Quasi two-dimensional perovskite solar cells (Q-2D PSCs) has attracted the attention of many researchers in recent years due to improved stability compared to their three-dimensional (3D) counterparts. However, the insulation of organic cation could hinder charge transfer between the octahedral sheets, thereby decreasing photoelectric performance of Q-2D PSCs. Here, the study of the synergistic effect of MACl and GuSCN on crystal orientation and quality of films based on the 4F‐PEA 2 MA 4 Pb 5 I 16 perovskite are reported. The Q-2D perovskite film exhibits more vertical orientation growth and lower trap-state density with the effect of dual additive. As a result, the device obtained a power conversion efficiency (PCE) of 15.05% for planar p-i-n solar cell using the Q-2D perovskite film with dual additive, which retained an average of 85% of their initial PCEs after 300 h in an ambient environment with humidity of 50 ± 10%. This result indicates that the use of dual additive MACl and GuSCN is an effective way to adjust the crystal orientation and quality of perovskite films, which are key factors to influence the performance of Q-2D PSCs. • The Q-2D perovskite film 4F‐PEA 2 MA 4 Pb 5 I 16 with dual additives (MACl and GaSCN) was prepared for the first time. • With the synergistic effect, the high-quality Q-2D perovskite film with more vertical orientation was obtained. • There was a larger concentration window of GaSCN additive in the presence of MACl due to their synergistic effect. • Compared with the Q-2D PSCs without additive, the PCE of Q-2D PSCs based on dual additives increased by 1.76 times.

Enhancing the Stability and Performance of Two-Dimensional Perovskite Solar Cells via Double-Step Homogeneous Precursor Mixing

Enhancing the Stability and Performance of Two-Dimensional Perovskite Solar Cells via Double-Step Homogeneous Precursor Mixing

Electron Transport Layer-Free Ruddlesden–Popper Two-Dimensional Perovskite Solar Cells Enabled by Tuning the Work Function of Fluorine-Doped Tin Oxide Electrodes

Organic–inorganic halide two-dimensional (2D) layered perovskites have been demonstrated to have better environmental stability than conventional three-dimensional perovskites. In this study, we investigate the fabrication of electron transport layer (ETL)-free Ruddlesden–Popper 2D perovskite solar cells (PSCs) by tuning the work function of a fluorine-doped tin oxide (FTO) electrode. With the deposition of polyethylenimine (PEIE) onto its surface, the work function of the FTO electrode could be raised from −4.72 to −4.08 eV, which is more suitable for electron extraction from the perovskite absorber. Using this technique, the ETL-free 2D PSCs exhibited an excellent power conversion efficiency (PCE) of 12.7% (on average), which is substantially higher than that of PSCs fabricated on a pristine FTO electrode (9.6%). Compared with the PSCs using TiO2, the ETL-free PSCs could be fabricated under a low processing temperature of 100 °C with excellent long-term stability. After 15 days, the FTO/PEIE-based ETL-free PSCs showed a PCE degradation of 16%, which is significantly lower than that of the TiO2-based case (29%). The best-performing PSC using a FTO/PEIE cathode showed a high PCE of 13.0%, with a small hysteresis degree of 2.3%.

Improving Lattice Rigidity and Charge Carrier Lifetime by Engineering Spacer Cation of Ruddlesden-Popper Perovskites: A Time-Domain Ab Initio Study.

First-principles quantum dynamics calculations show that charge carrier lifetimes, charge transport, and lattice stability are notably improved when BA (CH3(CH2)3NH3+) in BA2PbI4 is replaced with MTEA (CH3(CH2)2SNH3+). By suppressing atomic fluctuations, MTEA enhances the lattice stiffness and inhibits loss of coherence due to the S-S interaction. By delocalizing hole wave functions on the MTEA, particularly on the S atoms, while maintaining the electron wave functions largely unchanged compared to the BA2PbI4, MTEA serves to enhance charge transport and NA coupling while narrowing the bandgap by 0.18 eV. Overall, MTEA decreases NA coupling due to slow atomic motions against a large overlap of electron-hole wave functions, which suppresses nonradiative electron-hole recombination and prolongs carrier lifetime twice longer compared with BA2PbI4. This simulation presents a rational route to make high performance two-dimensional perovskite solar cells.

Scalable fabrication for efficient quasi two-dimensional perovskite solar cells via ultrasonic spray-coating method

The ultrasonic spray-coating process (USCP) has been proved to be desirable to fabricate the perovskite solar cells (PSCs) at high volume, especially for the three-dimensional perovskites. In this work, we extend this technique to the fabrication of two-dimensional (2D) PSCs due to a series of advantages of 2D PSCs, including long-term stability and excellent electrical properties. we apply this high-throughput deposition technology with an ultrasonic spray-coating system for forming the 2D perovskite which provides more possibility for the lab-to-fab translation. Due to the difference of crystal structure between 2D and 3D perovskites, the process of film formation is diverse which requires extra optimization to produce 2D perovskites in large scale. By comparing the perovskite quality deposited with different film deposition methods, we find layer-by-layer deposition method can provide a better film quality and more controllable film formation process. Hence, with this deposition method, we use USCP to realize an efficient batch production, obtaining an optimized power conversion efficiency of 10.5%, which is slightly lower than that (12.2%) of spin-coating processed samples. Moreover, devices based on USCP exhibit comparable long-term stability with the spin-coated devices. This report provides a promising alternative for the producing the 2D perovskite devices with high-throughput way.

A review on two-dimensional (2D) perovskite material-based solar cells to enhance the power conversion efficiency.

With perovskite materials, rapid progress in power conversion efficiency (PCE) to reach 25% has gained a significant amount of attention from the solar cell industry. Since the development of solid-state perovskite solar cells, rapid research development and investigation on structure design, device fabrication and fundamental studies have contributed to solid-state perovskite solar cells to be a strong candidate for next-generation solar energy. The promising efficiency with low-cost materials is the key point over the other material-based solar cells. The power conversion efficiency (PCE) of two-dimensional (2D) perovskite materials is yet to be enhanced in order to contest with the 3D perovskite-based solar cells. Their enormous variety compromises better prospects and possibilities for research. Two-dimensional (2D) perovskites play a multi-functional role within a solar cell, such as a capping layer, passivating layer, prime cell absorber, and in a hybrid 3D/2D perovskite-based solar cell absorber. This review summarizes the evolution of solar cells that are based on 2D perovskites and their prominent character in solar cells, along with the significant trends. The fundamental configuration and the optoelectronic characteristics, including the band orientation and the transportation of the charges, are discussed in detail. The 2D perovskites are analyzed to study the confined charges within the inorganic structure due to the dielectric and quantum confinement influence. Furthermore, the importance of cesium cation (Cs+) doped with 2D substance (BA)2(MA3) PbI3 approach has been discussed to attain high power conversion efficiency (PCE). These attributes offer an efficient step towards air-stable and small-sized perovskites as a new group of renewable energy sources.