High-performance Perovskite Solar Cells Research Articles

Chloride Engineering for Boosting Perovskite Photovoltaics: Impact on Precursor Coordination, Crystallization, and Film Quality.

Perovskite solar cells (PSCs) have seen rapid advancements over the past decade, driven by their exceptional optoelectronic properties and high power conversion efficiencies. Cl-based additives strategy has significantly contributed to these advancements by enhancing crystallinity, improving preferred orientation, and optimizing the surface morphology of perovskite films. This review provides a comprehensive summary of recent advancements and insights into the critical role of Cl-based additives in perovskite photovoltaics, focusing on the mechanisms behind Cl incorporation and its effects on film and device performance. First, the impact of Cl on precursor solution coordination and colloidal characteristics is discussed. Then, how Cl-based additives influence the phase transitions of perovskites, including methylammonium lead iodide (MAPbI3), formamidinium lead iodide (FAPbI3), and 2D perovskites is examined. Furthermore, the impact of Cl-based interfacial treatments on perovskite film quality is explored. Based on these insights, the overall impact of Cl treatments is also reviewed on the properties of perovskite films. Finally, a brief overview of the remaining challenges and future perspectives are provided to guide ongoing research efforts toward optimizing Cl additive engineering for high-performance PSCs.

Real-time three-dimensional monitoring and analysis of perovskite solar cell using short wavelength infrared digital holography

The quality and crystallization process of all-inorganic perovskite films play a crucial role in the performance of solar cells. However, traditional detection methods lack three-dimensional depth information and real-time capabilities, hindered by strong visible light absorption, posing challenges to research. Here, a simple digital holography technique is proposed that offers real-time, nondestructive, three-dimensional phase imaging with low absorption characteristics in the short-wave infrared range. The use of short-wave infrared reduces the negative impact of visible light and vibrations in the environment on detection accuracy, while being nearly non-absorbing. The proposed method operates at a speed of 15 Hz, combining a lensless vertical structure, holographic reconstruction algorithm, and phase unwrapping algorithm to achieve real-time three-dimensional observation without image distortion and with low noise of the crystallization process of CsPbBr3 perovskite quantum dots (PQDs)/ethylene-vinyl acetate solution, which crystallizes in 39 s. Subsequently, employing minimum bounding rectangle, field stitching, intensity registration, and sub-pixel level calibration algorithms, real-time characterization is performed on the large-sized droplet of polymethyl methacrylate-matrix-encapsulated CsPbBr3 perovskite quantum dots, which has a crystallization time of 1285 s, without being limited by the field of view. Finally, using this system, the surface quality of the film is assessed, revealing fluctuations at the edge and fabrication defects of the perovskite film. Experimental results demonstrate the potential of short-wave infrared digital holography in enhancing the film formation process and quality inspection. By leveraging this technology, advancements in the development of high-performance all-inorganic perovskite solar cells can be fostered, optimizing global energy output.

A X-bit optimized 2D solid solution Ti3CNTx MXene as the electron transport layer toward high-performance perovskite solar cells

Electron transport layer (ETL) materials need to have good photoelectric properties and suitable energy levels to match the perovskite layer. Ti3CNTx MXene, a typical two dimensional (2D) solid solution, is a potential ETL material due to excellent conductivity and appropriate work function (WF). Herein, Ti3CNTx is obtained by optimizing the X-bit inside MXene, and is firstly used as a new ETL for perovskite solar cells (PSCs). Compared with Ti3C2Tx, Ti3CNTx possesses lower WF due to the existence of N-H bonds. And the energy level between Ti3CNTx and the perovskite layer is more suited to reduce energy loss. Moreover, Ti3CNTx interacts with I- ions to passivate defects, enhancing the quality of the perovskite film. As expected, the better power conversion efficiency (PCE) of Ti3CNTx-PSC reaches 20.16 %, which is one of the most outstanding PCE among 2D materials used as ETLs. More interestingly, the Ti3CNTx-PSC possesses better stability (the PCE retention rate is 70.3 % after 600 h in the air), as a stronger Pb-O bond can reduce Pb0 formation. This work not only reveals the mechanism of interaction between 2D solid solution materials and perovskite, but also explores the vast application prospect of solid solution MXene in PSCs.

Rubidium Induced Phase Regulation for High-Performance Quasi-2D Perovskite Solar Cells

Rubidium Induced Phase Regulation for High-Performance Quasi-2D Perovskite Solar Cells

Surface Treatment via a Multifluorine-Containing Passivator for High-Performance Inorganic Perovskite Solar Cells

Surface Treatment via a Multifluorine-Containing Passivator for High-Performance Inorganic Perovskite Solar Cells

Scalable Slot-Die Coating of Passivation Layers for Improved Performance of Perovskite Solar Cell Modules.

Upscaling the perovskite solar cell (PSC) while avoiding losses in the power conversion efficiency presents a substantial challenge, especially when transitioning from ≤1cm2 cells to ≥10cm2 modules. In addition to the fabrication of key functional layers, scalable technologies for surface passivation, considered indispensable for achieving high-performance PSCs, are urgently required. However, studies on this topic remain limited. In this study, an industry-ready slot-die coating method for the effective passivation of perovskite films as a practical alternative is developed to the spin-coating procedures commonly used in research. The coating conditions and molecular structure of the passivation agent are systematically optimized to achieve high-quality film morphology and substantially suppress interface recombination. 2-chloro-5-(trifluoromethyl)-phenylammonium bromide exhibited the best results, improving the open-circuit voltage of cells and subcells in a module by 80±4 and 72±10mV, respectively. Correspondingly, the larger-area (active area: 10cm2) modules sustained the highest efficiency of 21.9% under simulated 1-sun irradiation. The encapsulated devices retained 94% of their initial performances after 750h of continuous operation. The proposed surface-passivation slot-die technology is compatible with high-throughput processes and is employable for large-scale PSC fabrication.

Simultaneous Suppression of Multilayer Ion Migration via Molecular Complexation Strategy toward High-Performance Regular Perovskite Solar Cells.

The migration and diffusion of Li+, I- and Ag impedes the realization of long-term operationally stable perovskite solar cells (PSCs). Herein, we report a multifunctional and universal molecular complexation strategy to simultaneously stabilize hole transport layer (HTL), perovskite layer and Ag electrode by the suppression of Li+, I- and Ag migration via directly incorporating bis(2,4,6-trichlorophenyl) oxalate (TCPO) into HTL. Meanwhile, TCPO co-doping results in enhanced hole mobility of HTL, advantageous energy band alignment and mitigated interfacial defects, thereby leading to facilitated hole extraction and minimized nonradiative recombination losses. TCPO-doped regular device achieves a peak power conversion efficiency (PCE) of 25.68 % (certified 25.59 %). The unencapsulated TCPO doped devices maintain over 90 % of their initial efficiencies after 730 h of continuous operation under one sun illumination, 2800 h of storage at 30 % relative humidity, and 1200 h of exposure to 65 °C, which represents one of the best stabilities reported for regular PSCs. This work provides a new approach to enhance the PCE and long-term stability of PSCs by host-guest complexation strategy via rational design of multifunctional ligand molecules.

Application of PACz-Based Self-Assembled Monolayer Materials in Efficient Perovskite Solar Cells.

Due to the advantages of low interface resistance, high work function, and high stability, PACz family materials have developed rapidly in p-i-n structure perovskite solar cells (PSCs) in recent years. Numerous studies have shown that PSCs prepared on the basis of PACz family materials or their derivatives as hole transport layers (HTLs) generally exhibit superior performance compared to PSCs prepared on the basis of organic HTL PTAA and inorganic HTL NiOx, especially in terms of stability, demonstrating unparalleled charm. Since the application of PACz-like molecule V1036 as a HTL in PSCs in 2018, research reports on high-performance PSCs based on the PACz family HTL have been widely disseminated. Currently, PSCs based on the PACz HTL exhibit a world record value of 26.7% power conversion efficiency (PCE), breaking the long-standing world record held by n-i-p-structured PSCs, indicating its great potential for application in PSCs. The main problem with using PACz as a HTL is that it exhibits poor wettability toward perovskite precursor solutions, is sensitive to the thickness of the HTL and the roughness of the substrate, has poor thermal stability, and lacks preparation methods, making it difficult to achieve large-area device fabrication. This review summarizes the outstanding achievements of PACz to date, describes the mechanism and unique properties of PACz in PSCs, and looks forward to the future development prospects of PACz.

Minimizing interfacial energy losses via fluorination strategy toward high-performance air-fabricated perovskite solar cells

Sub-bandgap state-induced radiative recombination and trap-assisted nonradiative recombination at the interface between the perovskite layer and hole transport layer in n-i-p perovskite solar cells (PSCs) significantly limit further improvements in power conversion efficiency (PCE) and stability. In this work, we introduce a simple yet effective fluorination strategy to mitigate these recombination losses by simultaneously achieving defect passivation, tensile strain release, and modulation of interfacial energy band alignment. The incorporation of fluorine (F) groups not only enhances defect passivation through strong chemical bonding but also improves the moisture resistance of perovskite films and devices. We reveal the critical influence of the number and position of F groups on the benzene ring in determining device photovoltaic performance. PSCs modified with 3,5-difluoro-benzamidine hydrochloride (3,5-DFBH) demonstrate a remarkable PCE of 24.57 %, coupled with enhanced long-term stability. These PSCs, among the highest-performing devices fabricated in ambient air, maintained over 90 % of their initial power conversion efficiency (PCE) after 2700 h of storage at 10 % to 20 % relative humidity, and withstood 1700 h of exposure to heat at 65 °C. This work provides a viable pathway to simultaneously improve both the photovoltaic performance and stability of PSCs by mitigating sub-bandgap and trap-assisted recombination through fluorination.

Advanced Surface Passivation Enables High-Performance Carbon-Based All-Inorganic Perovskite Solar Cells

Advanced Surface Passivation Enables High-Performance Carbon-Based All-Inorganic Perovskite Solar Cells

Cross-Linkable Fullerene Electron Transport Layer with Internal Encapsulation Capability for Efficient and Stable Inverted Perovskite Solar Cells.

A stable and compact fullerene electron transport layer (ETL) is crucial for high-performance inverted perovskite solar cells (PSCs). However, traditional fullerene-based ETLs like C60 and PCBM are prone to aggregate under operational conditions, a challenge recently recognized by academic and industrial researchers. Here, we designed and synthesized a novel cross-linkable fullerene molecule, bis((3-methyloxetan-3-yl)methyl) malonate-C60 monoadduct (BCM), for use as an ETL in PSCs. Upon a low-temperature annealing at 100 °C, BCM undergoes in-situ cross-linking to form a robust cross-linked BCM (CBCM) film, which demonstrates excellent electron mobility and a suitable band structure for efficient PSCs. Our results show that PSCs incorporating CBCM-based ETL achieve an impressive efficiency of 25.89% (certified: 25.36%), significantly surpassing the 23.25% efficiency of PCBM-based devices. The intramolecular covalent interactions within CBCM films effectively prevent aggregation and enhance film compactness, creating an internal encapsulation layer that mitigates the decomposition and ion migration of perovskite components. Consequently, CBCM-based PSCs show exceptional stability, maintaining 97.8% of their initial efficiency after 1000 hours of maximum power point tracking, compared to only 78.6% retention in PCBM-based devices after less than 820 hours.

Pyridalthiadiazole-Based Molecular Chromophores for Defect Passivation Enables High-Performance Perovskite Solar Cells.

Passivation of defects at the surface and grain boundaries of perovskite films has become one of the most important strategies to suppress nonradiative recombination and improve optoelectronic performance of perovskite solar cells (PSCs). In this work, two conjugated molecules, abbreviated as CPT and SiPT, are designed and synthesized as the passivator to enhance both efficiency and stability of PSCs. The CPT and SiPT contain pyridalthiadiazole (PT) units, which can coordinate with undercoordinated Pb2+ at the surface and grain boundaries to passivate the defects in perovskite films. In addition, with the incorporation of CPT, the crystallized perovskite films exhibit more uniform grain size and smoother surface morphology relative to the control ones. The efficient passivation by CPT also results in better charge extraction and less carrier recombination in PSCs. Consequently, the CPT-passivated PSCs yield the highest power conversion efficiency (PCE) of 23.14 % together with better storage stability under ambient conditions, which is enhanced relative to the control devices with a PCE of 22.14 %. Meanwhile, the SiPT-passivated PSCs also show a slightly enhanced performance with a PCE of 22.43 %. Our findings provide a new idea for the future design of functional passivating molecules towards high-performance PSCs.

Tetrabutylammonium Hydroxide-Functionalized Ti3C2Tx MXene for Significantly Improving the Photovoltaic Performance of Perovskite Solar Cells.

An appropriate electron transport layer (ETL) or cathode buffer layer (CBL) is critical for high-performance perovskite solar cells (PVSCs). In this work, tetrabutylammonium hydroxide (TBAOH)-functionalized Ti3C2Tx MXene (TBAOH-Ti3C2Tx) is developed to improve the photovoltaic performance of PVSCs. TBAOH-Ti3C2Tx is synthesized by HF etching and then TBAOH intercalation, and TBAOH can effectively attach to the Ti3C2Tx surface during the intercalation process. In hole transport material (HTM)-free carbon-based PVSCs with the structure of ITO/ETL/MAPbI3/carbon, the SnO2 doped by TBAOH-Ti3C2Tx (SnO2:TBAOH-Ti3C2Tx) as ETL shows decreased WF and increased conductivity and improves the growth of the perovskite film with a larger grain and significantly reduced defects, which synergistically facilitate charge transport and extraction and reduce charge recombination. The HTM-free carbon-based PVSC with SnO2:TBAOH-Ti3C2Tx ETL exhibits a significantly higher PCE of 14.93% with enhanced device stability compared to the control device with pristine SnO2 ETL (11.95%) and also outperforms most of the HTM-free carbon-based PVSCs with MAPbI3 perovskite reported so far. In traditional inverted PVSCs with the structure of ITO/PTAA/MAPbI3/PCBM/CBL/Ag, the TBAOH-Ti3C2Tx is utilized as a CBL to significantly enhance device performance with a high PCE of 21.16%, which is obviously superior than that (16.26%) of the control device without CBL. The impressive results indicate that tetrabutylammonium hydroxide-functionalized Ti3C2Tx MXene possesses great application potential in different functional layers for high-performance PVSCs.

Harnessing Cu2O-Doped 4-tert-Butylpyridine in Spiro-OMeTAD: Study on Improved Performance and Longevity of Perovskite Solar Cells.

Recently, spiro-OMeTAD has gained prominence as a hole-transporting material (HTM) in high-performance perovskite solar cells (PSCs) due to its superior properties, cutting-edge HOMO state of energy, and solution processability. To promote hole mobility and conductivity, hygroscopic dopants and additives such as lithium bis(trifluoromethanesulfonyl)imide (Li-TFSI) and 4-tert-butylpyridine (TBP) are typically incorporated. However, these components can lead to aggregation and hydrolysis in ambient conditions, forming pinholes and voids in the films. In this study, we introduce Cu2O as a spiro-OMeTAD additive to reduce voids and improve the quality of films. Incorporating Cu2O alleviates TBP evaporation and provides a more consistent dispersion of Li-TFSI, decreasing the formation of pinholes and bubbles. As a result, additional anions are added to spiro-OMeTAD+ during the oxidation process, promoting the conductivity and hole mobility of the hole-transporting layer and thus boosting PSC performance. Thus, the power conversion efficiency (PCE) percentage of the Cu2O-modified HTM reaches 14.17%, surpassing that of the control HTM at 12.25%. Furthermore, the introduction of Cu2O protects the perovskite layer from water-induced deterioration, ensuring the stability of the PSCs. Our findings offer a promising approach to enhancing both the performance and stability of HTMs and PSCs.

Fabrication of high-efficiency perovskite solar cells using benzodithiophene-based random copolymeric hole transport material

The design of donor-acceptor (D-A)-based random copolymers-type hole transporting materials (HTMs) are important for achieving superior performance of perovskite solar cells (PSCs) with high durability. In this work, a 2-alkylthienyl-substituted benzodithiophene (BDTT)-based random copolymer (denoted as RCP-BDTTPD), containing 2-ethylhexylthiophene-substituted benzo[1,2-b:4,5-b′]dithiophene (BDTT as an electron-donor; M1) and two different side-chain functionalized thieno[3,4-c]-pyrrole-4,6‑dione as the electron-acceptors (M2 and M3), is prepared and applied as an efficient interfacial HTM for PSCs. The optical, electrochemical, and electronic properties of RCP-BDTTPD are shown to be structurally and energetically viable to serve as HTM for PSCs. The RCP-BDTTPD has deeper highest occupied molecular orbitals (HOMO; −5.53 eV) and lowest unoccupied molecular orbitals (LUMO; −3.57 eV) energy levels. This is shown to be energetically suitable for realizing better compatibility with Cs-containing formamidinium/methylammonium (FAMA) mixed-cation perovskite as light absorber having HOMO energy level (−5.85 eV). The RCP-BDTTPD possessing gradient band alignment with perovskite, which is shown to be highly significant for the extraction of charge carriers, resulting in higher hole mobility of PSCs. RCP-BDTTPD delivered a reasonably good Voc of 1.10 V and higher Jsc of 19.01 mAcm−2 and, champion power conversion efficiency (PCE) up to 15.30 % with hole mobility (1.34×10−3 cm2V−1s−1) and high durability (Encapsulated cell retention of its PCE about 98 % over 16 h under harsh environment: Temp. ∼85 °C, RH∼85 %). This work demonstrating a potential application of RCP-BDTTPD based HTMs for the fabrication of high-performance PSCs with high durability as well as low cost.

Aromatic carboxyl acid regulated nanoparticle deposition and passivation of tin oxide for high performance perovskite solar cells

The composition and nano particle agglomeration of hydrolyzed species in chemical bath deposition (CBD) plays a key role in obtaining efficient SnO2 film for high performance perovskite solar cells (PSCs). In this work, the aromatic acids with varied carboxyl groups were investigated to regulate the nano particle deposition and passivate the buried SnO2/perovskite interface. The quasi in-situ dynamic light scattering and Zeta potential results indicated that the nano particle agglomeration with trimesic acid (TMA) was significantly refined throughout the whole deposition process. The TMA-SnO2 achieved an ideal energy band alignment with perovskite and released the internal residual strain, promoting the growth and crystallization of the perovskite film due to the corrdination of carboxyl groups. As a result, the interface defects were effectively passivated with enhanced efficiency and stability. The small area device based on TMA-SnO2 obtained an efficiency of 25.07 %. The devices with an enlarged area of 1.4 cm2 and the 5x5 cm2 mini-module (active area 10.054 cm2) showed impressive PCEs of 23.93 % and 22.40 %, respectively. Furthermore, the unencapsulated devices exhibit enhanced long-term stability, maintaining 80 % and 90 % of the initial efficiencies under 80 ± 5°C thermal annealing in nitrogen for 1176 h and in air condition for 3224 h, respectively.

Composition design of fullerene-based hybrid electron transport layer for efficient and stable wide-bandgap perovskite solar cells

Fullerene derivatives [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) has been routinely used as the electron transport layer (ETL) in perovskite solar cells due to its suitable energy levels and good solution processability. However, its electron mobility and conductivity still need to be further enhanced for constructing high performance perovskite solar cells (PSCs). Herein, by doping the PC61BM with a p-type polymer PM6 and n-type molecule ITIC, efficient wide-bandgap perovskite solar cells with improved efficiency and operational/storage stability are obtained. Further spectroscopy and electric measurements indicate PM6 and ITIC can both passivate defects at the perovskite/ETL interface, meanwhile ITIC can elevate the Fermi level of PC61BM to enhance conductivity and PM6 can improve the photo-induced electron mobility of the ETL, facilitating charge extraction and reducing charge recombination. As the results, Cs0.17FA0.83Pb(I0.83Br0.17)3 wide-bandgap PSCs with PM6:PC61BM:ITIC as the ETL demonstrates a superior efficiency of 22.95%, compared to 20.89% of the PC61BM assisted device.

Advancements in the photovoltaic optimization of a high performance perovskite solar cell based on graphene oxide (GO) hole transport layer

The increasing demand for efficient and sustainable green energy solutions has intensified the search for high-performance photovoltaic technologies. Herein, solar cell capacitance simulator (SCAPS-1D) is employed to simulate a novel solar cell design of the configuration, ITO/PC61BM/CH3NH3SnI3/GO/Fe. Various HTLs and electron transport layers (ETLs) are tested for comparison where graphene oxide (GO) HTL and PC61BM ETL exhibited exceptional electrical outcomes. The optimized PSC achieves a power conversion efficiency (PCE) of 36.27 % with Voc of 1.3462 V, Jsc of 34.84 mA/cm², and FF of 77.32 %. The built-in voltage (Vbi) of 0.31 V was derived from the band diagram at 300 K. Further exploration of the Mott-Schottky capacitance characteristics revealed that both donor and acceptor densities influence device performance. Notably, the Vbi remained stable at 0.32 V despite varying donor densities from 10¹⁰ cm⁻³ to 10¹⁹ cm⁻³, while increasing the acceptor density improved the Vbi from 0.2 to 0.72 V, suggesting remarkable operational performance at higher acceptor concentrations. This model device achieves maximum quantum efficiency of 100 % between 360 and 700 nm, therefore it exhibits a good photon capture for enhanced power conversion. Although the present study is based on numerical analysis, the findings inspire the promise of fabricating a physical solar cell of robust operational performance that can be injected into the production workflow for possible commercial scalability.

Low-temperature crosslinked hole transport material for high-performance inverted perovskite solar cells

Hole transport materials (HTMs) play a crucial role in the development of high-performance inverted perovskite solar cells (PSCs) by facilitating hole transport, passivating defects, and tuning crystallization. Achieving high efficiency and stability remains a key challenge for the PSCs. Crosslinked HTMs combine the efficiency of small molecules with enhanced environmental stability, however, a significant challenge in developing crosslinked HTMs for PSCs is the high temperature required for crosslinking. In this work, we synthesized a concise crosslinkable HTM, Tetrastyrenebiphenyldiamine (TPDA), based on a biphenyl core with four styrene groups, using a one-step method. TPDA can be crosslinked through an annealing process at 100℃ for 10 min without the need for any dopants or initiators. Interestingly, the compact films formed in the anneal process and the excellent spreadability for the perovskite precursor solution leading to the high-quality perovskite films, as a result, the inverted devices based on CL-TPDA achieve a champion power conversion efficiency (PCE) of 21.4%. Furthermore, the stability of the devices without encapsulation has notably improved. The PCE maintains over 85% of its initial value after 1000 h of storage in ambient air (25℃, relative humidity about 50%).

Enhancing the efficiency and stability of carbon-based perovskite solar cells through treatment of the CsPbI2Br surface with neostigmine bromide

Carbon-based all-inorganic perovskite solar cells (C-PSCs) are reknown for their inexpensive manufacturing process. However, the perovskite constituents in C-PSCs are susceptible to the formation of numerous structural defects and halide vacancies, which can induce substantial energy level misalignments between the light-absorbing layer and the carbon electrode. This discrepancy hinders the extraction and transfer of holes, thereby adversely affecting the overall efficiency of the device. In this study, we propose an interfacial post-treatment strategy aimed at reinforcing perovskite layers through the application of Neostigmine bromide (NMB) as a modifier. NMB effectively promoted the recrystallization of intrinsic phase segregation on the surface of CsPbI2Br film and enhanced the crystal integrity of perovskite surface. Furthermore, bromine ions (Br−) can occupy halide vacancies. Incorporating NMB at the interface significantly reduces the surface defect concentration of the perovskite layer and optimizes the energy level alignment with the carbon electrode. Experimental results demonstrate that the optimized device exhibits remarkable stability and achieves an striking power conversion efficiency (PCE) of 14.15%. This research lays the foundation for the development of cost-effective, high-performance, and durable all-inorganic perovskite solar cells.