Quality Of Perovskite Films Research Articles

Synergistic Effect of Alkylammonium Chlorides to Trigger an Ultrafast Nucleation for Antisolvent‐Free Perovskite Solar Cells Processed from 2‐Methoxyethanol

Abstract2‐Methoxyethanol (2ME), as a more environmentally friendly solvent with a lower boiling point compared to dimethylformamide, is ideal for the fabrication of perovskite solar cells (PSCs). However, when 2ME is used for antisolvent‐free deposition of perovskite films, an uncontrolled nucleation process and an easy phase transition to the δ‐phase often occur. Herein, an ultrafast nucleation process is developed using methylamine chloride (MACl) and n‐butylammonium chloride (BACl) as dual additives in 2ME without further solvent addition. While MACl can rapidly induce MACl‐based nuclei to initiate the nucleation process for formamidinium lead iodide (FAPbI3), the addition of BACl to the precursor with MACl can further increase the nucleation rate and density of nuclei, and bypass the transition from δ‐ to α‐phase during crystal growth to obtain a highly crystalline and pinhole‐free perovskite film. As a result, the FAPbI3 PSCs achieve a power conversion efficiency (PCE) of 23.6%. This work provides a new inspiration for controlling the crystal quality of perovskite thin films via nucleation rate suitable for upscaling.

Gamma-ray dose threshold for MAPbI3 solar cells.

In this work, we report on the effects observed in MAPbI3 polycrystalline films and solar cells under moderate gamma-ray doses of 3-21 kGy. We applied several instrumental techniques such as photoluminescence spectroscopy, time-resolved photoluminescence, Suns-VOC measurement, and impedance spectroscopy to characterize exposed samples. We observed a nonlinear dependency of such characteristics as PL intensity, career lifetime, ideality factor, and recombination resistance on the exposure dose. Small doses of 3-5 kGy annihilate some of the defect centers in the material, which results in improved carrier extraction and prolonged carrier lifetime, while with larger doses of 10 kGy and above, nonradiative recombination becomes predominant. In this way, we revealed a gamma-ray threshold for MAPbI3 films of around 10 kGy, above which it is not recommended to exploit this material. In space environment, yearly doses rarely exhibit 0.1 kGy (10 krad), and the MAPbI3 material has a sufficient margin of safety for space applications. Moreover, this unusual behaviour opens up the opportunity to use gamma-ray sources as an effective method to improve the quality of defective polycrystalline perovskite films before actual exploitation in an ionizing radiation-free environment.

Low-temperature curable TiO2 sol for separator and HTM-free carbon-based perovskite solar cells

A low-temperature curable TiO2 ETL for carbon-based perovskite solar cells was developed. The effect of the ETL surface energy on perovskite film formation and quality was assessed.

Cyclen molecule manipulation for efficient and stable perovskite solar cells

Cyclen regulated the perovskite film growth and healed Pb-relative defects. The corresponding perovskite solar cells achieved an impressive efficiency of 24.71%, and modules in 36 cm2 total-area gained a high efficiency of 20.08% via blade coating.

Organic ammonium salt assisted crystallization and defect passivation of a quasi-two-dimensional pure blue perovskite at the buried interface.

Quasi-two-dimensional (quasi-2D) perovskites exhibit excellent performance in light-emitting diodes (LEDs). However, the quality of perovskite films prepared via the solution method is significantly impacted by the enormous number of defects that unavoidably form at the grain boundaries and interfaces during the precursor to the crystal formation process. Here, we propose a strategy to assist perovskite crystallization and defect passivation at the buried interface through interfacial modification. The organic ammonium salt, ethylamine chloride (EACl), is added to the hole transport material and modifies the buried interface of the perovskite film. EACl introduces the nucleation sites for perovskite precursors, and promotes the crystallization process of the perovskite grains, contributing to the formation of high-quality perovskite films. At the same time, the presence of Lewis base (-NH2) groups in EACl and their lone electron pairs effectively inactivate unlocated Pb2+ ions at the buried interface, thereby reducing non-radiative recombination. In addition, chloride ions help to mitigate defects and to improve the morphology of perovskite films. Devices with this modification show a higher performance than control devices on all metrics. This work proposes a facile but efficient way for improving quasi-2D pure blue perovskite crystallization and growth.

SiW9Co3 @rGO composite-doping improved the crystallization and stability of a perovskite film for efficient photodetection.

The crystalline quality of perovskite films is a key factor that affects the performance of perovskite photovoltaic devices. Polyoxometalates can better match the energy levels of each layer in the devices through their own suitable energy level and band gap, and the good light absorption of POMs can also increase the mobility of photogenerated carriers in the devices. Moreover, POMs with Keggin-type structures can also improve the crystalline quality of perovskite films by eliminating defect sites, which can lead to better crystallization of perovskites with larger grains. In this study, we optimized the crystalline quality of a perovskite layer using the SiW9Co3@rGO composite prepared using POMs and graphene derivatives. XRD and SEM tests show that the crystallization degree of the perovskite layer was improved, the average grain size of which can reach up to 1222.92 nm, which is nearly four times higher than that of a blank perovskite. The photoresponse current of a SiW9Co3@rGO-doped photodetector can reach to 43.94 μA, which is about 226% higher than that of an undoped device. At the same time, the addition of the composite can improve the stability of photodetectors because of the special network structure of graphene. Photodetectors doped with SiW9Co3@rGO can still maintain more than 90% of their high performance for a month. This study proves that POM-based composites have good application prospects in the field of photovoltaic devices.

Synergistic nucleation regulation using 4,4',4''-tris(carbazol-9-yl)-triphenylamine and moisture for stably air-processed high-performance perovskite photodetectors.

Perovskite photodetectors (PPDs) offer a promising solution with low cost and high responsivity, addressing the limitations of traditional inorganic photodetectors. However, there is still room for improvement in terms of the dark current and stability of air-processed PPDs. In this study, 4,4',4''-tris(carbazol-9-yl)-triphenylamine (TCTA) was utilized as a nucleation agent to enhance the quality of perovskite films. The synergistic effect of TCTA and moisture promotes rapid nucleation of PbI2-PbCl2, resulting in an increased nucleation rate and the elimination of pinholes in the film. By employing additive engineering, we obtained a PbI2-PbCl2 layer with high coverage, leading to a low density of traps in the corresponding perovskite film. Consequently, the modified PPD exhibits a remarkable reduction in dark current density by over one order of magnitude, reaching 2.4 × 10-10 A cm-2 at -10 mV, along with a large linear dynamic range (LDR) of 183 dB. Furthermore, the resulting PPD demonstrates remarkable stability, retaining 90% of the initial external quantum efficiency (EQE) value even after continuous operation for over 3200 hours. Owing to a fast response time in the nanosecond range, the PPD could convert modulated light signals into electrical signals at a speed of 588 Kbit s-1, highlighting the great potential in the field of optical communication.

Strain engineering improves the photovoltaic performance of carbon-based hole-transport-material free CsPbIBr2 perovskite solar cells.

Alkylamines with different chain lengths including n-butylamine, n-hexylamine, and n-octylamine, are applied to regulate the CsPbIBr2 perovskite film quality by strain engineering. The status of residual strains is controllably modulated, resulting in improved efficiency and stability of carbon-based hole-transport-material free CsPbIBr2 perovskite solar cells.

Intermediate Phase Modification Enables High‐Performance Iodine‐Rich Inorganic Perovskite Solar Cells with 3000‐Hour Stability

AbstractThe presence of excess secondary‐phase PbI2 in perovskite films shows a negative impact on their long‐term stability. Herein, an intermediate phase modification (IPM) strategy is proposed to eliminate residual PbI2 for improved quality of all‐inorganic CsPbI3‐type perovskite films, wherein the extrinsic agent is introduced to address the intermediate phase. By transforming residual PbI2 into a novel 1D perovskite phase, the IPM strategy acts as a patch to suture grain boundaries in the inorganic perovskite films. In addition, the IPM strategy not only enhances the quality of perovskite films but also mitigates energy disorder, reduces trap state density, and prolongs carrier lifetime by expediting the intermediate phase conversion process and passivating surface defects. As such, the perovskite solar cells (PSCs) with a high power conversion efficiency (PCE) of ≈20% and a high fill factor of 83.3% are considered to be very efficient, with excellent shelf stability of 3000 h of exposure in air without any encapsulation. This work not only exhibits a novel optimization route for inorganic perovskite but also emphasizes the crucial role of eliminating residual PbI2 in inorganic perovskites.

Enhancement of Interfacial Properties by Indoloquinoxaline‐Based Small Molecules for Highly Efficient Wide‐Bandgap Perovskite Solar Cells

AbstractInterfacial engineering in organic–inorganic hybrid perovskite solar cells (PSCs) has attracted significant attention, aiming to achieve high‐performing and highly stable devices. Here, newly designed organic small molecules based on quinoxaline and triphenylamine for inverted type wide‐bandgap PSCs are introduced, with the objective of enhancing the interfacial properties between perovskite and NiOx hole transport layer (HTL). The incorporation of an organic interlayer effectively reduces the energy level offset between the HTL and wide‐bandgap perovskite, while passivating defects within the perovskite layer. It leads to improved charge extraction and minimized non‐radiative recombination at the interface. Furthermore, the enhanced interfacial characteristics and hydrophobicity contribute to the improvement of perovskite film quality, resulting in larger grain size and higher crystallinity. As a result, the power conversion efficiency (PCE) of the PSC is enhanced from 18.9% to 20.1% with the incorporation of the IQTPAFlu interlayer, accompanied by an increase in Voc to ≈1.3 V, achieving a significantly low Voc deficit of 0.46 V. And the IQTPAFlu‐based devices demonstrate stable and consistent performance over 500 h, with ≈91% of their initial PCE retained. The highly stable wide‐bandgap PSCs, characterized by high Voc and PCEs, hold great promise as potential candidates for tandem solar cells.

Interfacial bidirectional binding for improving photovoltaic performance of perovskite solar cells

SnO2 as an electron transport layer (ETL) has recently been used for perovskite solar cells (PSCs) due to high transmittance and electron mobility. However, the mismatched band energy alignment of ETL and perovskite layer result in serious nonradiative recombination limiting the improvement of PSCs performance. Here, 2-(Diphenylphosphino)ethanaminium tetrafluoroborate (DPEBF4) as buried interface was introduced between ETL and perovskite. The [BF4]− anion in DPEBF4 can interact with SnO2 to reduce the surface defect of SnO2. While [DPE]+ cation is more inclined to interact with Pb2+ and I−, the terminal strong interaction will promote crystallization of perovskite film quality and passivate buried surface defects. As a result, device performance was significantly improved by introducing DPEBF4 layer, the power conversion efficiency (PCE) increase from 20.50 % for control devices to 23.84 %. The work provides an interfacial double-tonic strategy for ETL and perovskite crystals to achieve high-performance perovskite photovoltaic devices.

Antisolvent-Free Heterogenous Nucleation Enabled by Employing 4-Tert-Butyl Pyridine Additive and Two-Step Annealing for Efficient CsPbI2Br Perovskite Solar Cells.

All inorganic perovskite based on CsPbI2Br has attracted significant attention due to its relatively thermal stable structure compare to its hybrid counterparts. With a wide bandgap of 1.9eV and excellent light absorption capability, it has been extensively explored for applications in indoor photovoltaics and as a front absorber in tandem devices. However, the uncontrollable crystallization process during solvent evaporation and thermal annealing leads to both macroscopic defects like cracks and microscopic defects such as voids. In this study, a metastable adduct with lead (II) halides by incorporating 4-tert-butyl pyridine as a volatile Lewis base monodentate ligand in the precursor solution is formed. The strategic preferential decomposition of the adduct during the early-stage low-temperature annealing facilitated the desorption of lead (II) halides, inducing antisolvent-free heterogenous nucleation. This, in turn, promoted crystal growth during subsequent high-temperature annealing, resulting in dense films with low defect density. As a result, a maximum open-circuit voltage of 1.30V is achieved with the champion power conversion efficiency of 16.5% in CsPbI2Br-based perovskite solar cell. The work reveals a new mechanism of using Lewis acid-base adduct to obtain high quality perovskite films other than hindering crystallization in traditional way.

Triethylsilane introduced precursor engineering towards efficient and stable perovskite solar cells

Perovskite solar cells (PSCs) are believed to be optimistic for commercial deployment soon since the power conversion efficiency of PSCs presently reaches up to 26.10 % due to the intensive efforts these years. The two-step method is comparatively more suitable for scalable perovskite films, where lead halides and ammonium salts are prepared in separate precursors and deposited sequentially. Therefore, the reactivity between these two precursors governs the quality of final perovskite films and the intrinsic non-radiative recombination (NRR) at the perovskite's interfaces. Herein, we empowered both types of precursors, one by one and then simultaneously, with triethylsilane (TES) to investigate its effect on the (FAPbI3)1-x (MAPbBr3)x perovskite's morphological and optoelectronic properties. TES, with ethyl moieties and metalloid center, in ammonium salts delivers homogeneous perovskites' crystals and inhibits the NRR of perovskite films by reducing the defects and trap states. As a result, the optimized devices exhibit not only improved device performance (particularly for the increased fill factors and open circuit voltages) but also enhanced stabilities.

Gd3+–Ho3+-Dy3+]:CsPbI2.2Br0.8: Lanthanide impelled stabilization of perovskite material for sustainable energy harvesting, generation, and charge storage

This work presents the first systematic investigation of the novel [Gd3+–Ho3+-Dy3+]:CsPbI2.2Br0.8 (GHD:CPVSK) hetero-structure and explores it for energy applications. The optical constancy of GHD:CPVSK was explored for 28 days and it spanned around 1.63 – 1.68 eV, expressing remarkable stability in band energy. This material was identified with the cubic phase and possessed typical ABX3 type of crystalline geometry. GHD:CPVSK was used as an absorber layer inside regular perovskite solar cell. It improved the overall photovoltaic operation with the 16.56 % efficiency and 75.89 % fill factor reflecting the excellent perovskite film quality. As an electro-catalyst, the pure hydrogen production activity of GHD:CPVSK excelled over oxygen generation with the lower overpotential and Tafel slope value of 142 mV and 117.3 mV dec−1. Also, this electro-catalyst was electrochemically intact in electrolyte environment for 100 min. In terms of the charge storing capacity for battery, GHD:CPVSK embellished electrode has 470.66 mAh g−1 of unit capacity and impressively minimal equivalent series resistance (Rs) of 0.41 Ω. The developed material stabilized by lanthanide doping has expressed excellency for diverse energy associated applications and systems in a cost effective, facile, and sustainable manner.

A Practical Approach Toward Highly Reproducible and High-Quality Perovskite Films Based on an Aging Treatment.

Solution processing of hybrid perovskite semiconductors is a highly promising approach for the fabrication of cost-effective electronic and optoelectronic devices. However, challenges with this approach lie in overcoming the controllability of the perovskite film morphology and the reproducibility of device efficiencies. Here, a facile and practical aging treatment (AT) strategy is reported to modulate the perovskite crystal growth to produce sufficiently high-quality perovskite thin films with improved homogeneity and full-coverage morphology. The resulting AT-films exhibit fewer defects, faster charge carrier transfer/extraction, and suppressed non-radiative recombination compared with reference. The AT-devices achieve a noticeable improvement in the reproducibility, operational stability, and photovoltaic performance of devices, with the average efficiency increased by 16%. It also demonstrates the feasibility and scalability of AT strategy in optimizing the film morphology and device performance for other perovskite components including MAPbI3 , (MAPbBr3 )15 (FAPbI3 )85 , and Cs0.05 (MAPbBr3 )0.17 (FAPbI3 )0.83 . This method opens an effective avenue to improve the quality of perovskite films and photovoltaic devices in a scalable and reproducible manner.

Controlling the grain formation process with oleylamine and 4-dimethylaminopyridine additives for efficient and stable MAPbI3 solar cells

MAPbI3-based perovskite solar cells (PSC) prepared on one-dimensional structured electron transport layers (ETL) have been widely investigated due to excellent photovoltaic properties. However, they have displayed lower stability and power conversion efficiencies compared to other perovskite solar cells such as FAPbI3 and mixed halide perovskites. To improve the quality of perovskite film, we treat MAPbI3 perovskite layer with oleylamine (OAm) and 4-dimethylaminopyridine (DMAP) during preparation. Modified MAPbI3 layers are prepared by spin coating OAm-added precursor solution on ETLs and the DMAP solution is dripped on the rotating substrate during spin coating process. The OAm additive not only enhances significantly the perovskite crystallinity but also reduces the number of pin-holes inside perovskite thin films. The drip starting time of DMAP solution strongly affects the nanostructures of perovskite layer and the PSC performances. The best efficiency of PSC in this study is 20.49 % and is the highest cell performance compared to other MAPbI3-based PSCs using TiO2 nanorod thin films as ETLs in literature. The remarkable enhancement of PSC performance is assigned to the synergetic effects of both DMAP and OAm at the grain boundaries of MAPbI3 layer. Furthermore, the use of OAm and DMAP leads to significant enhancement of device's stability under ambient conditions.

An Extraordinary Antisolvent Ethyl Cyanoformate for Achieving High Efficiency and Stability P3HT‐Based CsPbI3 Perovskite Solar Cells

AbstractSurface defects are always a severe problem in inorganic perovskite, superadding the mismatch of energy level between Poly(3‐hexylthiophene) (P3HT) hole transport layer (HTL) and CsPbI3 perovskite. All these issues result in large losses in open‐circuit voltage (Voc) and fill factor (FF), and thus, CsPbI3 perovskites solar cells (PSCs) based on P3HT HTL commonly show a lower power conversion efficiency (PCE). Herein, an extraordinary antisolvent engineering is proposed by ethyl cyanoformate (EC), that regulates the crystallization progress to improve the quality of CsPbI3 perovskite film. Concomitantly, residual EC passivates the uncoordinated Pb2+ defects by synergistical chemical interaction of C≡N and C═O groups, and energy level arrangement at the CsPbI3/P3HT interface is also optimized. As a result, the PCE of P3HT‐based CsPbI3 PSC is improved to 18.46% from 17.33% of the control device. The unencapsulated CsPbI3 PSCs show enhanced moisture stability and fine operational stability. The work reveals that EC is an extraordinary antisolvent, exhibiting a synergistic strategy in many aspects for obtaining high‐performance P3HT‐based CsPbI3 PSCs. Furthermore, P3HT is doped with a small amount of 4‐Cyano‐4′‐pentylbipheny (5CB), and thus the PCE of PSC is increased to 19.15% and its humidity stability is significantly improved.

Reducing Nonradiative Losses of Air‐Processed Perovskite Films via Interface Modification for Bright and Efficient Light Emitting Diodes

AbstractDeveloping ambient‐air fabrication strategy is desirable for lowering down the fabrication cost of perovskite light emitting diodes (LEDs) and further promoting their broad applications. However, ambient humidity usually leads to undesirable interface and perovskite film quality, causing severe nonradiative losses and unsatisfactory device performance. In this work, an effective strategy to solve this problem and remarkably enhance the performance of perovskite LEDs is reported. The study reveals that the humidity‐induced aggregation of self‐assembled monolayer (SAM) in humid air can be eliminated by introducing a poly[(9,9‐bis(3′‐((N,N‐dimethyl)‐N‐ethylammonium)‐ propyl)‐2,7‐fluorene)‐alt‐2,7‐(9,9‐dioctylfluorene)] dibromide (PFNBr) as an interface modifier, which reduces the interfacial defects and improves the perovskite crystallinity. The interaction between PFNBr and perovskite can further passivate the defects and suppress trap‐assisted nonradiative processes, which significantly enhances the photoluminescence efficiency of the ambient‐processed perovskite films. Furthermore, the energy level alignment is optimized and the hole injection is improved, thus resulting in more efficient and balanced charge injection. As a result, the green perovskite LEDs achieve a high external quantum efficiency of 12.06% and luminance of 22121 cd m−2, representing the record values for the perovskite LEDs processed under such ambient‐air condition, in accompany with an improved device stability.

Defect passivation by a betaine-based zwitterionic molecule for high-performance p-i-n methylammonium-based perovskite solar cells

The quality of perovskite films plays a vital role in the performance of perovskite solar cells (PSCs). Additive engineering has been proven to be an effective strategy for reducing defects in perovskite films. In this study, a betaine-based zwitterionic molecule, [2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide (denoted as SBMA), is employed as an additive in p-i-n PSCs. SBMA can passivate the defects in two ways: (1) The ester groups and SO32− passivate the positively charged defects. (2) Quaternary ammonium ions can passivate the negatively charged defects. The addition of SBMA reduces the trap density in the perovskite films, and therefore, nonradiative recombination is effectively suppressed. A champion power conversion efficiency (PCE) as high as 21.39% for p-i-n PSCs based on CH3NH3PbI3 is achieved, and the thermal and humidity stability is improved. Moreover, when the active area was increased to 0.27 cm2 and 1.1 cm2, the device with SBMA could achieve PCEs of 20.18% and 18.43%, respectively.

Ionic‐Liquid‐Assisted Fabrication of High‐Performance Methylammonium‐Free Perovskite Solar Cells via Smoothed‐Interface Engineering

A judicious modification of the buried interface can enhance the quality of perovskite films and reduce non‐radiative recombination losses, particularly in methylammonium (MA)‐free perovskite solar cells (PSCs). In this study, the ionic‐liquid 1,3‐dimethylimidazolium methanesulfonate (DMIMMeSO4) is employed, characterized by its high ionic conductivity and excellent thermal stability, to regulate the perovskite/SnO2 interface. The nitrogen component in DMIMMeSO4 can interact with Sn4+ through Lewis acid–base interactions, effectively passivating defects associated with tin and suppressing the formation of oxygen vacancies, leading to reduced non‐radiative recombination of charge carriers. In addition, [MeSO4]− can also form coordination bonds with PbI2, creating a better perovskite film with smoothed interface. Moreover, DMIMMeSO4 also optimize the energy‐level alignment, thereby reducing the charge‐transfer barrier and enhancing charge‐extraction efficiency. As a result, power conversion efficiency of 23.91% is achieved by MA‐free PSCs modified with DMIMMeSO4. Furthermore, after 1000 h of ambient air storage, devices that are not encapsulated maintaine over 90% efficiency. In all of these results, it is clearly indicated that interface modulation based on ionic‐liquid‐assisted smoothed‐interface engineering is an effective approach for obtaining high‐performance PSCs.