Power Conversion Efficiency Of Perovskite Solar Cells Research Articles

High‐Performance Inverted Perovskite Solar Cells by Dual Interfaces Modification with Identical Organic Salt

AbstractThe improvement of power conversion efficiency (PCE) and stability of perovskite solar cells (PSC) relies on the enhanced quality of perovskite layer and the modification of its adjacent interfaces. For this purpose, a multifunctional organic passivation molecule 1‐(4‐Fluorophenyl) biguanide hydrochloride (F‐BHCl) is introduced to the top and bottom interfaces of the perovskite layer. The PCE of PSC after the modification of double interfaces with F‐BHCl is significantly increased from 22.41% (unmodified) to 25.14%, and the storage, thermal, and operation stability is also improved. The comprehensive theoretical and experimental studies verify that due to its versatile functional groups and adaptation, F‐BHCl can significantly improve the quality of perovskite film, fully passivate several kinds of common defects, smoothen the top surfaces of perovskite film, and construct “molecular bridges” with carrier transporters on both the top and bottom surfaces, leading to significantly reduced non‐recombination and carrier transport losses. As a result, a significant increase is achieved in the open circuit voltage and fill factor as well as the whole performance of the device.

Buried interface modification toward efficient perovskite solar cell based on PVK hole transport layer

Poly (9-vinylcarbazole) (PVK) is an attractive hole transport material for organometallic-halide perovskite solar cell (PSC) because of its excellent hole transport ability and great film-forming property. Nowadays, the PVK hole-transport-layer (HTL) based PSC suffered from low power conversion efficiency (PCE), which mainly caused by bad interface contact between PVK and perovskite film, including the energy level mismatch. Doing PVK is an effective and facial method to modify the buried interface of perovskite film. In this work, 1,1-bis [(di-4-tolylamino)phenyl]cyclohexane (TAPC) was added into PVK HTL. Experimental results show that a highest occupied molecular orbital (HOMO) level elevation was achieved after doping TAPC. Meanwhile perovskite films with increased crystallinity, reduced defect density and enhanced light absorbance were obtained. Finally, the PCE of PSCs were enhanced from 10.81% of the control device to 15.65% of PVK + 40% TAPC device. The reason that responsible for the energy level lifting, morphology improvement and performance enhancement were thoroughly investigated and analyzed. This work provides an alternative option for the dopant in PVK to improve the buried interface of perovskite film, and therefore, the performance of PSCs.

High-Quality TiO2 Electron Transport Film Prepared via Vacuum Ultraviolet Illumination for MAPbI3 Perovskite Solar Cells.

The electron transport layer (ETL) plays an important role in determining the conversion efficiency and stability of perovskite solar cells (PSCs). Here, TiO2 thin film was prepared by irradiating diisopropoxy diacetylacetone titanium precursor thin film with 172 nm vacuum ultraviolet (VUV) at a low temperature. The prepared TiO2 thin film has higher electron mobility and conductivity. As it is used as an ETL for MAPbI3 PSCs, its band structure is better matched with the perovskite, and at the same time, due to the good interface contact, more uniform perovskite crystals are formed. Most importantly, a large number of hydroxyl radicals were formed during VUV irradiation of the precursor film, which made up for the oxygen defect present on the surface of the TiO2 thin film, and were adsorbed to the film surface. These hydroxyl groups form hydrogen bonds with methylammonium (MA) components on the MAPbI3 buried surface, thus promoting the transfer of photogenerated electrons at the MAPbI3/ETL interface. The power conversion efficiency of PSCs fabricated in air with the ETL prepared by VUV irradiation is 20.46%, which is higher than that of the contrast solar cell based on the sintered ETL (17.96%).

DFT Investigation of Structural Stability, Optical Properties, and PCE for All-Inorganic Csx(Pb/Sn)yXz Halide Perovskites.

Employing all-inorganic perovskites as light harvesters has recently drawn increasing attention owing to the strong-bonded inorganic components in the crystal. To achieve the systematic and comprehensive understanding for the structures and properties of Csx(Pb/Sn)yXz (X = F, Cl, Br, I) perovskites, this work provides the comparison details about crystal structures, optical properties, electronic structures and power conversion efficiency (PCE) of 18 perovskites. The suitable band gaps are detected in CsSnCl3-Pm3̅m (0.96 eV), γ-CsPbI3-Pnma (1.75 eV), and CsPbBr3-Pm3̅m (1.78 eV), facilitating the conversion from absorbing photon energy to generating hole-electron pairs. γ-CsPbI3-Pnma and CsSnI3-P4/mbm show superior visible-absorption performance depending on their higher absorption coefficient (α); meanwhile, strong peaks can be observed in the real part (Re) of photoconductivity of CsPbBr3-Pbnm, γ-CsPbI3-Pnma, and CsSnI3-P4/mbm in the visible-light range, implying their better photoelectric conversion abilities. The perovskite/tungsten disulfide (WS2) heterojunctions are constructed to calculate the PCE. Although just the PCE result (14.43%) of CsSnI3-Pnma/WS2 is reluctantly competitive, the predictions of PCEs indicate that the PCE of PSCs (perovskite solar cells) can be improved by not only regulating the perovskite to upgrade its own performance but also designing the PSC structure reasonably including the selection of appropriate ETL/HTL (electron/hole transport layer), etc.

Data‐Driven Approach to Accelerate the Design of Halide Perovskite for Photovoltaic Application Using Electronic Properties as Descriptors

Perovskite solar cells (PSCs) have garnered remarkable attention for their efficiency and tunable optoelectronic properties. However, their instability to moisture and heat poses challenges. Traditional trial‐and‐error approaches for finding stable halide perovskites are inefficient due to the vast compositional possibilities within ABX3 perovskite structure. This study uses machine learning (ML) to predict bandgaps and photovoltaic parameters of PSCs, using a dataset of 447 data points containing chemical composition, bandgaps, and photovoltaic parameters. Various ML models including support vector regressor, random forest, gradient boost regressor, XGBoost, extratree Regressor, and AdaBoost Regressor have been used herein. Positional average elemental property (PAEP) approach is introduced to featurize the data. As ABX3 perovskite involves distinct A, B, and X sites, the proposed PAEP model captures site‐specific effects, enhancing model accuracy. The best model exhibits impressive r‐values of 0.98 for bandgap prediction and 0.86 for power conversion efficiency of PSCs. Elemental properties of B and X sites, such as ionization energy, electron affinity, and electronegativity, are found to be crucial features in the analysis by Shapley additive explanation. This study underscores the potential of ML in designing novel, stable, and efficient PSCs, offering a more efficient alternative to conventional trial‐and‐error methods.

A regulation strategy of self-assembly molecules for achieving efficient inverted perovskite solar cells.

Self-assembled monolayers (SAMs) have been successfully employed to enhance the efficiency of inverted perovskite solar cells (PSCs) and perovskite/silicon tandem solar cells due to their facile low-temperature processing and superior device performance. Nevertheless, depositing uniform and dense SAMs with high surface coverage on metal oxide substrates remains a critical challenge. In this work, we propose a holistic strategy to construct composite hole transport layers (HTLs) by co-adsorbing mixed SAMs (MeO-2PACz and 2PACz) onto the surface of the H2O2-modified NiOx layer. The results demonstrate that the conductivity of the NiOx bulk phase is enhanced due to the H2O2 modification, thereby facilitating carrier transport. Furthermore, the hydroxyl-rich NiOx surface promotes uniform and dense adsorption of mixed SAM molecules while enhancing their anchoring stability. In addition, the energy level alignment at the interface is improved due to the utilization of mixed SAMs in an optimized ratio. Furthermore, the perovskite film crystal growth is facilitated by the uniform and dense composite HTLs. As a result, the power conversion efficiency of PSCs based on composite HTLs is boosted from 22.26% to 23.16%, along with enhanced operational stability. This work highlights the importance of designing and constructing NiOx/SAM composite HTLs as an effective strategy for enhancing both the performance and stability of inverted PSCs.

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.

Controlling Lead Halide Residue in Perovskite Solar Cells: A Method to Improve the Photostability and Hysteresis

The presence of residual lead iodide phase in perovskite films, inherent to the two‐step spin‐coating method, has been reported to be beneficial for the performance of perovskite solar cells (PSCs); However, it may potentially undermine the photostability of PSCs. Herein, four distinct sets of perovskite films and devices are fabricated via the two‐step spin‐coating process, each under different processing conditions. All conditions demonstrate promising power conversion efficiency in PSCs. However, the aspect of photostability is found to be significantly influenced by unreacted PbI2 in the perovskite films. Varying degrees of residual PbI2 are detected among these films. Upon light exposure, it is observed that residual PbI2 within perovskites undergoes decomposition into metallic lead (Pb0) and mobile iodine, and these can affect the photovoltaic performance of the PSCs. The presence of mobile ions in metal–halide perovskites has generated substantial concern due to their impact on hysteresis within the J–V curve. Furthermore, the metallic lead (Pb0) containing perovskite films exhibits a prominent inverted hysteresis in the J–V curve

Preliminary exploration of the influence of N+/NHx+ ions/groups bombardment at TiO2 ETLs on performance of MAPbI3 perovskite solar cells

The service stability of organic–inorganic hybrid metal halide perovskite solar cells (PSCs) is one of most important factors, which is seriously influenced by the decomposition of perovskite layer. Especially, the decomposition of perovskite layer could deteriorate the interface between perovskite layer and TiO2 electron transport layer (ETL). In this work, TiO2 ETLs are prepared by the sputtering technique and traditional spin-coating technique. Then, TiO2 ETLs are bombarded by N+/NHx+ ions/groups. PSCs with all TiO2 ETLs are prepared and measured. The results show that after bombardment, N+/NHx+ ions/groups could chemically react with Ti/O ions at surface of TiO2 ETLs. As a result, the conduction band minimum and transfer resistance of TiO2 ETLs both deteriorate, which decrease the power conversion efficiency of PSCs seriously. While, because anatase TiO2 (001) crystal face consists of saturated O/Ti ions and displays the highest surface free energy, TiO2 ETLs with anatase (001) preferred orientation displays the optimal restraint on deterioration of power conversion efficiency caused by N+/NHx+ ions/groups bombardment. Based on above results, TiO2 ETLs with anatase (001) preferred orientation should be the optimal one for PSCs, which could improve the service stability obviously.

Two birds with one stone: dopant-free squaraine hole-transporting material for perovskite solar cell

Developing alternative dopant-free hole-transporting materials (HTM) with a passivation effect and high hole mobility is significant for enhancing the power conversion efficiency (PCE) and stability of the perovskite solar cells (PSCs) with a simplified process. In this work, we report a squaraine HTM 3,4-bis(4'-(bis(4-methoxyphenyl)amino)-[1,1′-biphenyl]-4-yl)cyclobut-3-ene-1,2-dione (D12) with a resonance central structure shuttling between electrically neutral dione and charge-separated inner salts. The donor-acceptor-donor type molecule D12 exhibits an extremely strong capacity not only for hole exaction and mobility, but also for the passivation of perovskite defects. This results in a high PCE of 22.32% for D12-based PSCs. After 30 days of aging at a high relative humidity of 65% at 30 °C, it remains 90% of its initial PCE. This work offers a strategy of designing dopant-free small-molecule HTM and enhancing the stability and PCE of PSCs.

The Role of Alpha‐Methylbenzyl Ammonium Iodide to Reduce Defect Densities in Perovskite Devices

Hybrid organic–inorganic perovskite photovoltaic has achieved unmatched power conversion efficiency (PCE) improvement in the last decade. Nevertheless, nonradiative recombination of charge carriers due to bulk and interface defects reduces the open‐circuit voltage (V oc) and PCE of perovskite solar cells. Incorporating additives, process optimization, and interface engineering are among the effective approaches employed to reduce such issues. Herein, quasi‐2D p–i–n perovskite solar cells incorporating alpha‐methylbenzyl ammonium iodide (MBAI) cation with outstanding photovoltaic performance and stability are developed. MBAI incorporation results in films with excellent optical and electrical properties, leading to higher V OC of ≈1.15 V, fill factor of above 77%, and stability of the device. A high open‐circuit voltage and fill factor and corrected power conversion efficiencies in the range of 15% are obtained for the prepared devices. The encapsulated solar cells show excellent operational stability under white light illumination in ambient air for >500 h. Due to the simple and robust preparation process, the investigated inverted perovskite solar cell can easily be combined with other solution‐processed thin film solar cells to form multijunction devices and can easily be integrated into different lightweight and flexible products.

Defect Regulation of Efficient Dion-Jacobson Quasi-2D Perovskite Solar Cells via a Polyaspartic Acid Interlayer.

Interfacial modification is a promising strategy to fabricate highly efficient perovskite solar cells (PSCs). Nevertheless, research studies about optimization for the performance of Dion-Jacobson (DJ)-phase quasi-2D PSCs by underlying surface modification are rarely reported. The relevant influence of interfacial modification on defect regulation in the bulk and at the interface for PSCs is still unexplored. Herein, an interlayer of polyaspartic acid (PASP) was introduced at the interface of a hole transporting layer and a perovskite absorber to regulate both the film quality and interface property for BDA-based DJ quasi-2D PSCs (n = 5). The PASP interlayer suppressed the charge recombination, restricted the interfacial charge accumulation, and promoted the charge transport in devices and therefore improved the power conversion efficiency of PSCs from 15.03 to 17.34%. Moreover, through device simulation, it was concluded that the increase of open-circuit voltage (Voc) was mainly attributed to the suppression of interface defects, while the increase of short-circuit current (Jsc) was ascribed to the restriction of interface defects and perovskite bulk defects. The improvement of both Voc and Jsc originated from the passivation of shallow defect states. The present work provides a promising route for the fabrication of efficient quasi-2D PSCs and enriches the fundamental understanding of defect regulation on photovoltaic performance.

A functionalized phosphorous tetrabenzotriazacorrole dye as a novel passivating agent of high-performance planar perovskite solar cells

Surface passivation is a crucial strategy to manage the film characteristics of solution-processed perovskite absorber layers, which greatly impact the photovoltaic properties of perovskite solar cells (PSCs). However, designing and synthesizing suitable passivating agents with required functional groups and solution-processability is challenging due to their complex molecular structure. In this study, we demonstrate a facile passivation technique using a functionalized phosphorous tetrabenzotriazacorrole dye (PTBC) for p-i-n PSCs. The tetrabenzotriazacorrole dye has amines and ether linkages that can closely interact with the undercoordinated Pb2+ with halogen vacancies through Lewis acid-base interactions, leading to a pinhole-free perovskite absorber layer with reduced trap density. Moreover, the central phosphorus of PTBC is functionalized with dimethoxy groups, which can provide a more hydrophobic surface in the perovskite absorber layer. Consequently, high-quality perovskite films (CsFAPbI3) prepared with PTBC exhibit improved optical, electrical, and morphological properties, as well as superior carrier transportation/recombination kinetics, boosting the power conversion efficiency of PSCs from 17.64 % to 20.08 %, with over 75 % of initial efficiency preserved after 1000 h of aging under ambient conditions. These results highlight PTBC as an effective surface passivation agent for perovskite absorber layers and emphasize the importance of suitable passivating agents in optimizing PSC performance.

Direct interface engineering using dopant of hole transport layer for efficient inorganic perovskite solar cells

With respect to the aim of achieving a suitable optical band gap and high thermal and chemical stability in next-generation perovskite solar cells (PSCs), inorganic CsPbI3 perovskite has gained significant attention. However, when it absorbs light, it quickly transforms into an undesired nonperovskite yellow phase at 25 °C. Therefore, it is crucial to stabilize the phase by reducing the defect density, which acts as a nonradiative recombination center at the interface of each layer. In this paper, we present an efficient interface treatment method that does not require any additional surface treatment such as annealing or coating, and the dopant Mn(TFSI)2 is directly mixed with the hole transporting material instead of bis(trifluoromethane)sulfonimide lithium salt (Li-TFSI). The use of Mn(TFSI)2 as a dopant diminishes the interfacial defects between the perovskite and hole transporting layer, reducing nonradiative recombination, increasing the lifetime of the carrier, and improving the power conversion efficiency from 16.5% for the control device using conventional Li-TFSI as a dopant to 17.6%. Moreover, the Mn(TFSI)2-doped device demonstrates superior long-term stability for 1000 h under ambient conditions without encapsulation, demonstrating 95% efficiency when compared with the initial performance. Therefore, Mn(TFSI)2 is a more powerful dopant of HTL and can increase the power conversion efficiency of PSCs by passivating the interface between the perovskite and HTL. Using Mn(TFSI)2, it is possible to quickly and effectively manufacture a stable inorganic perovskite device.

Enhancement in Power Conversion Efficiency of Perovskite Solar Cells by Reduced Non-Radiative Recombination Using a Brij C10-Mixed PEDOT:PSS Hole Transport Layer.

Interface properties between charge transport and perovskite light-absorbing layers have a significant impact on the power conversion efficiency (PCE) of perovskite solar cells (PSCs). Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is a polyelectrolyte composite that is widely used as a hole transport layer (HTL) to facilitate hole transport from a perovskite layer to an anode. However, PEDOT:PSS must be modified using a functional additive because PSCs with a pristine PEDOT:PSS HTL do not exhibit a high PCE. Herein, we demonstrate an increase in the PCE of PSCs with a polyethylene glycol hexadecyl ether (Brij C10)-mixed PEDOT:PSS HTL. Photoelectron spectroscopy results show that the Brij C10 content becomes significantly high in the HTL surface composition with an increase in the Brij C10 concentration (0-5 wt%). The enhanced PSC performance, e.g., a PCE increase from 8.05 to 11.40%, is attributed to the reduction in non-radiative recombination at the interface between PEDOT:PSS and perovskite by the insulating Brij C10. These results indicate that the suppression of interface recombination is essential for attaining a high PCE for PSCs.

Lithium Fluoride Assisted Preparation of High‐Performance All‐Inorganic CsPbI3 Perovskite Solar Cells

All‐inorganic CsPbI3 perovskite is an ideal solar material with an appropriate bandgap (≈1.73 eV) that can be used for the top cell in tandem cells matched to crystalline silicon or low‐bandgap perovskites. Efficient all‐inorganic perovskite solar cells (PSCs) provide the cornerstone for efficient tandem cells. However, all‐inorganic PSCs are less efficient than organic–inorganic hybrids PSCs, and because CsPbI3 is incompatible with water, the stability of perovskite must be improved. Herein, a novel method for preparing efficient and stable PSCs via ionic chemical doping is proposed. Lithium fluoride as an inorganic ionic dopant can control grain growth and get larger grain sizes. The crystal structure, morphology, and electrochemical impedance spectroscopy of LiF‐doped all‐inorganic perovskite films are studied to determine the relationship between film quality and device performance. The doping of 2 mol% LiF considerably enhances the performance of the device, eliminates the hysteresis effect of the device, and the maximum power conversion efficiency of PSCs is raised to 17.02%. Additionally, device stability is greatly enhanced.

Recent Advances in g-C3N4 for the Application of Perovskite Solar Cells.

In this study, graphitic carbon nitride (g-C3N4) was extensively utilized as an electron transport layer or interfacial buffer layer for simultaneously realizing photoelectric performance and stability improvement of perovskite solar cells (PSCs). This review covers the different g-C3N4 nanostructures used as additive and surface modifier layers applied to PSCs. In addition, the mechanism of reducing the defect state in PSCs, including improving the crystalline quality of perovskite, passivating the grain boundaries, and tuning the energy level alignment, were also highlighted in this review. Currently, the power conversion efficiency of PSCs based on modified g-C3N4 has been increased up to 22.13%, and its unique two-dimensional (2D) package structure has enhanced the stability of PSCs, which can remain stable in the dark for over 1500 h. Finally, the potential challenges and perspectives of g-C3N4 incorporated into perovskite-based optoelectronic devices are also included in this review.

Efficient Perovskite Solar Cells via Phenethylamine Iodide Cation-Modified Hole Transport Layer/Perovskite Interface.

Perovskite solar cells (PeSCs) were fabricated by using CsxFA1–xPbI3–xClx as the photoactive layer, and the effects of different proportions of cesium chloride (CsCl)/formamidinium iodide on perovskites were investigated. Cesium (Cs) can stabilize the α phase of the perovskite, while chlorine (Cl) can increase the size and crystallinity of perovskite crystals and reduce non-radiative cladding, thereby improving the performance of the overall device. The maximum power conversion efficiency (PCE) measured for Cs0.2FA0.8PbI2.8Cl0.2-based PeSCs was 18.9%. To further improve the photovoltaic characteristics of PeSCs, Cs0.2FA0.8PbI2.8Cl0.2-based PeSCs were introduced into different concentrations of phenethylammonium iodide (PEAI) to modify the interface between the NiOx hole transport layer (HTL) and the perovskite photoactive layer, which can simultaneously promote excellent crystallinity of the perovskite layer and passivated interfacial defects, reducing recombination near the perovskite/HTL interface in PeSCs, thereby increasing the efficiency of the device. Compared with the control Cs0.2FA0.8PbI2.8Cl0.2-based PeSC, the PCE of PeSC with the PEAI (10 mg/mL)-modified NiOx/perovskite interface increased significantly from 18.9 to 20.2%.

Spiro-OMeTAD-Based Hole Transport Layer Engineering toward Stable Perovskite Solar Cells.

Perovskite solar cells (PSCs) have undergone unprecedented growth in the past decade as an emerging photovoltaic technology. Up till now, the power conversion efficiency of PSCs has exceeded 25% that rivals silicon solar cells and there is still room for further enhancement. However, the development in long-term stability lags far behind, which remains a great concern for the commercial application in the future. The device instability mainly arises from the functional components, including perovskite film, charge transport layers, and electrodes along with the involved interfaces. As the most widely studied hole transport layer at the current stage, 2,2',7,7'-tetrakis(N,N-di(4-methoxyphenyl)amino)-9,9-spirobifluorene (Spiro-OMeTAD) helps contribute to the achievement of record efficiency but it weakens the device stability due to the doping-induced side effects such as hygroscopicity and ion migration. Great efforts are devoted to boosting the stability of Spiro-OMeTAD while maintaining excellent photovoltaic performance. In this review, the fundamental properties of Spiro-OMeTAD have been summarized and the recent advances in engineering Spiro-OMeTAD-based hole transport layer for the sake of highly efficient PSCs with enhanced longevity are highlighted. In the end, an outlook for the further optimization of Spiro-OMeTAD is provided and the issues related to large-scale production are discussed.

Amorphous TiO2 film with fiber like structure: An ideal candidate for ETL of perovskite solar cells

• E T L A m o r p h o u s T i O 2 was prepared by DCP-MS at room temperature. • Lots fiber like structures run through the E T L A m o r p h o u s T i O 2 directly. • Fiber like structures in E T L A m o r p h o u s T i O 2 improves electron transfer efficiency. • PCE of PSCs improves from 4.7% of E T L A n a t a s e T i O 2 to 11.5% of E T L A m o r p h o u s T i O 2 . Organic-inorganic hybrid metal halide perovskite solar cells (PSCs) with planar heterojunction structures were fabricated. The amorphous and anatase TiO 2 electron transfer layer (ETL) was deposited by the direct current pulsed magnetron sputtering technology. With the ordinary CH 3 NH 3 PbI 3 , PSCs with amorphous and anatase TiO 2 ETL showed the average power conversion efficiency in (11.5 ± 0.7)% and (4.7 ± 1.5)%, respectively. Combining with XRD and TEM results, the fiber like structure in amorphous TiO 2 ETL resulted in the increase of average power conversion efficiency of PSCs. Finally, amorphous TiO 2 with fiber like structure is an ideal ETL for PSCs, which is prepared by sputtering.