Perovskite Active Layer Research Articles

Additive and Interface Engineering via Crosslinked 3D Polymer Network for Efficient and Stable Perovskite Solar Cells

In this study, a facile and promising strategy is presented to enhance the performance and stability of perovskite solar cells (PeSC) by incorporating tri(ethylene glycol) divinyl ether (TEGDVE) as the additive and dopant for perovskite active layer and amine‐functionalized perylene diimide (PDIN) cathode interfacial layer, respectively. The results indicate that the electron‐donating oxygen atoms of TEGDVE can interact with undercoordinated Pb2+ via the formation of coordination bond, which synchronously passivates the defects within perovskite film and manipulates the crystallization kinetics. Additionally, the vinyl functional groups on TEGDVE can undergo thermal cross‐linking reaction and form three‐dimensional polymer network, enabling perovskite film to possess good optoelectronic properties and enhanced moisture stability. In addition, the incorporation of TEGDVE can induce n‐doping of PDIN due to its adequate electron donation capability offered by oxygen atoms. With these appealing features, the resulting device delivers not only high power conversion efficiency up to 20.90% but also satisfied ambient stability, greatly outperforming those of the PeSC without TEGDVE. This work provides a new avenue to improve the efficiency and stability of PeSC based on a facile strategy. The findings present a significant step towards the practical applications of this emerging technology.

Exploring the Efficiency of CH3NH3SnBr3/CsPbI3 Heterojunction Solar Cell using Numerical Simulation

This study presents a numerical analysis of heterojunction perovskite solar cells (PSCs) with a proposed structure of Glass/ETL/i-CH3NH3SnBr3/CsPbI3/HTL using the SCAPS-1D software. The primary objective is to investigate the influence of the thickness of CsPbI3 perovskite active layers with iCH3NH3SnBr3 as the permeable layer. Additionally, the power conversion efficiency (PCE), temperature dependence, quantum efficiency, open-circuit voltage (Voc), fill factor (FF), short-circuit current density, and J-V curve simulations for varying Na are examined. The highest PCE achieved was 42 %, accompanied by an FF of 90 %, Voc of 1.29 V, and Jsc of -35,42 mA/cm2. The findings of this analysis contribute to the understanding of the performance and optimization of heterojunction perovskite solar cells, highlighting the significance of layer thickness and device parameters in achieving high-efficiency solar energyconversion.

Enhancing the efficiency and scalability of perovskite solar cells through pseudo-halide salt addition

Organic–inorganic halide perovskites have significant potential for application in next-generation solar cells. However, their applications are limited by challenges associated with large-area processability and long-term stability owing to the presence of pinholes and defect sites. Here, we incorporated cesium formate in a perovskite active layer using a sequential perovskite fabrication process to eliminate the defect sites of perovskites and improve the film processability via roll-to-roll (R2R) processing. The addition of cesium formate salt to the PbI2 layer influences the perovskite crystal formation behavior as well as increases the perovskite crystallinity and decreases the defect density. Furthermore, cesium formate addition eliminated small PbI2 grains and smoothed the perovskite surface, resulting in a large crystal grain size. The formate ions interact with the PbI2 component and passivate halide vacancy defects, reducing nonradiative recombination and improving charge transfer. Additionally, the treated perovskite films were highly stable in air, exhibiting improved efficiency retention over time and achieving a power conversion efficiency (PCE) of > 22% compared to the control. Furthermore, the additive-treated perovskite film was processed using the R2R method, achieving a high PCE of >14% with minimal hysteresis.

Simulation of efficient Sn/Pb-based formamidinium perovskite solar cells with variation of electron transport layers

Numerical modelling on functional Sn-based perovskite solar cells (PSCs) has been performed and compared with Pb-based PSCs by using general-purpose photovoltaic device model software. The effect of variation in active layer thickness and various electron transport layers (ETLs), including tin oxide (SnO2), zinc oxide, C60, titanium dioxide, phenyl-C61- butyric acid methyl ester, on the photovoltaic parameters of Sn-based PSCs has been investigated. The active layer thickness was observed to be 500 nm, and SnO2 as ETL material resulted in the most efficient PSC. The optimized Sn-based device with formamidinium tin iodide as perovskite active layer shows promising results with a maximum power conversion efficiency of 24.41% compared to 27.49% for formamidinium lead iodide-based device. Further, other photovoltaic parameters for lead free PSC devices are quite comparable as for lead-based devices, showing the potential of Sn-based perovskite material as a fair candidate to replace toxic Pb-based-PSCs.

Pinhole-free 2D Ruddlesden–Popper perovskite layer with close packed large crystalline grains, suitable for optoelectronic applications

Here, we achieved pinhole-free 2D Ruddlesden–Popper Perovskite (RPP) BA2PbI4 layers with close packed crystalline grains with dimension of about 30 × 30 µm2, which have been demonstrated to be favorable for optoelectronic applications, such as fast response RPP-based metal/semiconductor/metal photodetectors. We explored affecting parameters in hot casting of BA2PbI4 layers, and proved that oxygen plasma treatment prior to hot casting plays a significant role to achieve high quality close packed polycrystalline RPP layers at lower hot cast temperatures. Moreover, we demonstrate that crystal growth of 2D BA2PbI4 can be dominantly controlled by the rate of solvent evaporation through substrate temperature or rotational speed, while molarity of the prepared RPP/DMF precursor is the dominant factor that determines the RPP layer thickness, and can affect the spectral response of the realized photodetector. Benefiting from the high light absorption and inherent chemical stability of 2D RPP layers, we achieved high responsivity and stability, and fast response photodetection from perovskite active layer. We achieved a fast photoresponse with rise and fall times of 189 µs and 300 µs, and the maximum responsivity of 119 mA/W and detectivity of 2.15 × 108 Jones in response to illumination wavelength of 450 nm. The presented polycrystalline RPP-based photodetector benefits from a simple and low-cost fabrication process, suitable for large area production on glass substrate, a good stability and responsivity, and a promising fast photoresponse, even around that of exfoliated single crystal RPP-based counterparts. However, it is well known that exfoliation methods suffer from poor repeatability and scalability, which make them incompatible with mass production and large area applications.

Surface Modification of ZnO Nanocrystals with Conjugated Polyelectrolytes Carrying Different Counterions for Inverted Perovskite Light-Emitting Diodes.

In this work, bromide ions (Br-) on the conjugated polyelectrolytes (CPEs) were converted to tetrafluoroborate (BF4-) or hexafluorophosphate (PF6-) ions through anion exchange. The three CPEs (PFN-Br, PFN-BF4, and PFN-PF6) were utilized solely for surface modification of zinc oxide nanocrystals (ZnO NCs). The ionic groups on CPEs can form permanent dipoles to facilitate charge injection from ZnO NCs to cesium lead bromide (CsPbBr3) NC emitters, therefore promoting luminescent properties of inverted perovskite light-emitting diodes (PeLEDs). The experimental results reveal that ZnO NC films were smoothened by CPEs that allowed flat deposition of the perovskite active layers; moreover, the improved contact between ZnO and perovskite layers was beneficial for reducing leakage current, as verified in the dark current measurement of devices. In addition, the incorporation of CPEs helped to passivate the defects of ZnO NC films and prolong the carrier lifetime of CsPbBr3 NCs. PeLEDs based on different CPEs were then constructed and evaluated. The device based on PFN-Br showed the highest brightness and current efficiency, and the one based on PFN-BF4 exhibited better current efficiency over PFN-Br under the low current density below 160 mA/cm2. This is the first report using fluorene-based CPEs with Br-, BF4-, or PF6- groups to modify the properties of ZnO and CsPbBr3 NCs for the construction of inverted PeLEDs so far. Our experiments explored new kinds of CPEs on the surface modification of ZnO NCs and device performance of PeLEDs.

Cellulose acetate-derived ternary-doped hierarchically porous carbons blended perovskite active layers for solar cells and X-ray detectors

Herein, we have synthesized hetero-atoms (nitrogen (N), sulfur (S), phosphorus (P))-doped porous carbons (PCs) which upon dispersion in perovskite precursor solution with different (2–8 wt.%) modify its morphology and improve optoelectronic characteristics of the perovskite active layer (AL) results into enhancing efficiency and stability of perovskite solar cells (PSCs). The results indicate that PCs (6 wt.%) modifies perovskite AL-constructed PSCs and X-ray photodetectors outperform other investigated devices. The excellent PSCs (AL@NSPCPC) demonstrate power conversion efficiency (PCE) of 13.81%, fill factor (FF) 64.77%, current density Jsc (23.518 mA/cm2), and open circuit voltage Voc (0.906 V), which is significantly higher than pristine AL 10.42%, 57.01%, 20.423 mA/cm2, and 0.895 V, respectively. Furthermore, the sample (AL@NSP-CPC) when constructs in the geometry of an X-ray photodetector, shows 15.56 μA/cm2, 4.66 mA/Gy·cm2, 5.26×10−4 cm2/V·s, and 3.58 × 1015 cm−3 of collected charge density (CCD), dark current density (DCD), sensitivity, mobility, and trap density, respectively. Thus, heteroatom-doped PCs modified perovskite layers demonstrate promise for constructing PSCs and X-ray photodetectors opening future research in exploiting these abundant, and inexpensive carbons materials having large mobility and tunable morphology along with surface passivation at perovskite/hole transport layer (HTL) interface to further enhance their photovoltaic parameters.

Zr-metal–organic framework based cross-layer-connection additive for stable halide perovskite solar cells

The poor stability of metal halide perovskite seriously affects the large-scale commercial application of perovskite solar cells (PSCs). Here, a large-particle Zr-based metal–organic framework (Zr-MOF), e.g. UiO-66 (NH2), is added to the precursor solution of SnO2 electron transport layer (ETL), realizing a cross-layer modification of (1) ETL, (2) perovskite active layer and (3) theirs interface simultaneously. We find that the SnO2 particles are dispersed into the ordered porous scaffold of Zr-MOF, to form an ETL with improved crystallinity, reduced defect states and increased contact area with active perovskite film. For the subsequently deposited perovskite layer, the crystallization along the vertical direction is significantly optimized, and the defects are passivated by the bottom-up infiltrated Zr-MOF, so as to suppress the ion migration process. The power conversion efficiency (PCE) of one-step fabricated Zr-MOF-modified MAPbI3 based PSCs is optimized from 17.48% to 18.25%, and remaining 99% of its initial value after storage for 800 h under ambient conditions with the relative humidity over 60%. This work provides a simple cross-layer passivation strategy to improve the performance and stability of PSCs using highly designable MOF materials.

Long-chain anionic surfactants enabling stable perovskite/silicon tandems with greatly suppressed stress corrosion

Despite the remarkable rise in the efficiency of perovskite-based solar cells, the stress-induced intrinsic instability of perovskite active layers is widely identified as a critical hurdle for upcoming commercialization. Herein, a long-alkyl-chain anionic surfactant additive is introduced to chemically ameliorate the perovskite crystallization kinetics via surface segregation and micellization, and physically construct a glue-like scaffold to eliminate the residual stresses. As a result, benefiting from the reduced defects, suppressed ion migration and improved energy level alignment, the corresponding unencapsulated perovskite single-junction and perovskite/silicon tandem devices exhibit impressive operational stability with 85.7% and 93.6% of their performance after 3000 h and 450 h at maximum power point tracking under continuous light illumination, providing one of the best stabilities to date under similar test conditions, respectively.

Plasma damage-free deposition of transparent Sn-doped In2O3 top cathode using isolated plasma soft deposition for perovskite solar cells

We developed an isolated plasma soft deposition (IPSD) technique for the plasma damage-free deposition of a Sn-doped In2O3 (ITO) top cathode on semi-transparent perovskite solar cells (PSCs). Unlike the directly faced plasma in conventional magnetron sputtering, the isolated plasma region in the IPSD process prevents the direct irradiation of plasma and facilitates plasma damage-free sputtering. Effective confinement of high-density plasma in isolated regions by using a specific Nd-Fe-B45 magnet array also prevents irradiation of energetic particles sputtered from faced ITO targets. In addition, linear scanning of the substrate in the isolated plasma region resulted in a low-temperature and large-area coating of the ITO top cathode without plasma damage for semi-transparent PSCs. Without intentional substrate heating, the IPSD-processed ITO film with a thickness of 100 nm under optimal conditions exhibited a low sheet resistance of 33.02 Ohm/square, high optical transmittance of 91.27%, root mean square roughness of 0.252 nm, and work function of 4.33 eV. To demonstrate the feasibility of IPSD, we fabricated PSCs with thermally evaporated perovskite active layers. Compared with the power conversion efficiency (PCE: 4.35%) of PSCs with magnetron-sputtered ITO cathode, the PSC with IPSD-processed ITO cathode exhibited a similar PCE (15.52%) because of the absence of plasma damage. Considering the commercialization of PSCs, the IPSD-based top cathode coating process possesses great potential as a key technique for bidirectional or semi-transparent PSCs.

Highly Stable Perovskite Solar Cells by Reducing Residual Water‐Induced Decomposition of Perovskite

Comprehensive SummaryResidual water‐induced decomposition is one of the dominant reasons for the decay of power conversion efficiency (PCE) in perovskite solar cells (Pero‐SCs). To solve this problem, we introduce traces amount of sodium hyaluronate (SH) into the perovskite active layer to reduce the remaining water during the preparation of perovskite films. Unlike the traditionally adopted passive protection of perovskite from exterior water by low surface energy coatings, this study provides active control of the interior water by the addition of a water adsorbent into the perovskite films. The encapsulated Pero‐SCs with SH retain approximately 70% of their initial PCE in 4000 h, while those without SH retain 32% of their initial PCE in 1000 h under the dark and ambient atmosphere. The unencapsulated Pero‐SCs with SH stored in N2 atmosphere maintain over 94% of the initial PCE in 3000 h at room temperature away from light and remain over 88% of the initial PCE in 2000 h even the devices are heated to 70 °C. It has been proven that the improved stability is mainly due to the well‐controlled residual water in perovskite films. Concomitantly, the PCE of p‐i‐n solar cells based on (FAPbI3)0.85(MAPbBr3)0.15 is improved from 19.34% to 21.54%.

SnO2 electron transport layer modified by F/N-doped graphdiyne and in situ XRD and in situ XAFS exploration on its effect on perovskite active layer

Electron transport layer (ETL) plays an important role in the perovskite solar cells. The graphdiyne oxide (GDYO), nitrogen-doped GDYO (NGDYO) or fluorinated GDYO (FGDYO) was added into SnO2 ETL, respectively, which optimized the properties of SnO2 layer itself and the interface between ETL and perovskite layer, and then affected the growth of perovskite. The mechanism was systematically explored by using in situ synchrotron radiation technology combined with conventional characterization methods. Though NGDYO-SnO2 enhanced the properties such as conductivity and energy level of ETL, FGDYO-SnO2 showed the best crystallization. By tracking the growth process of SnO2, PbI2 or perovskite by in situ XRD and the chemical bonds on the interface between ETL and active layer by in situ XAFS, it was found that the stronger interaction between the doped SnO2 with PbI2 inhibited PbI2 crystallization in perovskite layers and gave more opportunity for PbI2 precursor to form perovskite, making perovskite to have better crystallization. Finally, the optimized performance of device was achieved.

Numerical Analysis of Stable (FAPbI3)0.85(MAPbBr3)0.15-Based Perovskite Solar Cell with TiO2/ZnO Double Electron Layer.

Although perovskite solar cells have achieved excellent photoelectric conversion efficiencies, there are still some shortcomings, such as defects inside and at the interface as well as energy level dislocation, which may lead to non-radiative recombination and reduce stability. Therefore, in this study, a double electron transport layer (ETL) structure of FTO/TiO2/ZnO/(FAPbI3)0.85(MAPbBr3)0.15/Spiro-OMeTAD is investigated and compared with single ETL structures of FTO/TiO2/(FAPbI3)0.85(MAPbBr3)0.15/Spiro-OMeTAD and FTO/ZnO/(FAPbI3)0.85(MAPbBr3)0.15/Spiro-OMeTAD using the SCAPS-1D simulation software, with special attention paid to the defect density in the perovskite active layer, defect density at the interface between the ETL and the perovskite active layer, and temperature. Simulation results reveal that the proposed double ETL structure could effectively reduce the energy level dislocation and inhibit the non-radiative recombination. The increases in the defect density in the perovskite active layer, the defect density at the interface between the ETL and the perovskite active layer, and the temperature all facilitate carrier recombination. Compared with the single ETL structure, the double ETL structure has a higher tolerance for defect density and temperature. The simulation outcomes also confirm the possibility of preparing a stable perovskite solar cell.

Synthesis of Self-organic Assembly Monolayers to Improve the Stability of Perovskite Films

In recent years, photovoltaic devices based on perovskite materials have become one of the energy conversion field’s most in study topics. FAPbI3 stands out among a wide variety of perovskite structural materials with the advantages of a suitable band structure, long carrier diffusion distance, and so on. Unfortunately, the FAPbI3 perovskite films still lack some stability. It is well known that UV light and humidity strongly affect perovskite solar cell (PSC) performances, leading to the service life-time limitation of the device. Here, we propose strategies to improve the stability of PSCs by means of the interface engineering [1] between the electron transport layer and the perovskite active layer by inserting the self-organic assembled monolayers (SAMs). [2] The derivatives of Triethoxy(4-methoxyphenyl)silane (SAM1) and Triethoxy(3,4-dimethoxyphenyl)silane (SAM2) were synthesized using Grignard reaction [3] then inserted between the electron transport layer and perovskite active layer of PSC test devices in order to improve the hydrophobicity of the cell. Preliminary results showed that the perovskite active layers that have been modified with SAMs appear denser than those without modification. The overall conversion efficiency and stability of the SAMs-modified PSC devices will be further tested to prove more stable than those of unmodified devices.

Plasma damage control via adjusting the target to substrate distance used to prepare semi-transparent perovskite solar cells

To realize semi-transparent perovskite solar cells (ST-PSCs), a high-quality amorphous transparent cathode must be deposited on the perovskite active layer without plasma damage at room temperature. In this study, we have investigated the effect of the target-to-substrate distance (TSD) on the performance of ST-PSCs during linear facing target sputtering (LFTS) to achieve the plasma damage-free sputtering of Ga and Ti co-doped In2O3 (IGTO) upper cathodes on planar ST-PSCs. We comprehensively compare the electrical, optical, structural, and morphological properties of IGTO cathodes grown using different TSDs and correlate them to performances of the ST-PSCs to determine the optimal TSD. We demonstrate the importance of optimal TSD and deposition mechanism at different TSDs based on the properties of the resulting IGTO films and ST-PSC performance. At an optimal TSD of 6 cm, the amorphous IGTO film demonstrate a sheet resistance of 9.22 Ω/sq. and optical transmittance of 87.74%. The ST-PSC constructed using the optimized IGTO upper cathode exhibit an open-circuit voltage of 1.12 V, short circuit current of 20.23 mA/cm2, fill factor of 83.73%, power conversion efficiency of 18.91%, and average transmittance of 19.31%. Consequently, the choice of the TSD is crucial in LFTS process for the fabrication of high-performance ST-PSCs without plasma damage.

Application of Natural Molecules in Efficient and Stable Perovskite Solar Cells.

Perovskite solar cells (PSCs), one of the most promising photovoltaic technologies, have been widely studied due to their high power conversion efficiency (PCE), low cost, and solution processability. The architecture of PSCs determines that high PCE and stability are highly dependent on each layer and the related interface, where nonradiative recombination occurs. Conventional synthetic chemical materials as modifiers have disadvantages of being toxic and costly. Natural molecules with advantages of low cost, biocompatibility, and being eco-friendly, and have improved PCE and stability by modifying both functional layers and interface. In this review, we discuss the roles of natural molecules on PSCs devices in terms of the perovskite active layer, interface, carrier transport layers (CTLs), and substrate. Finally, the summary and outlook for the future development of natural molecule-modified PSCs are also addressed.

SCAPS Empowered Machine Learning Modelling of Perovskite Solar Cells: Predictive Design of Active Layer and Hole Transport Materials

Recently, organic–inorganic perovskites have manifested great capacity to enhance the performance of photovoltaic systems, owing to their impressive optical and electronic properties. In this simulation survey, we employed the Solar Cell Capacitance Simulator (SCAPS-1D) to numerically analyze the effect of different hole transport layers (HTLs) (Spiro, CIS, and CsSnI3) and perovskite active layers (ALs) (FAPbI3, MAPbI3, and CsPbI3) on the solar cells’ performance with an assumed configuration of FTO/SnO2/AL/HTL/Au. The influence of layer thickness, doping density, and defect density was studied. Then, we trained a machine learning (ML) model to perform predictions on the performance metrics of the solar cells. According to the SCAPS results, CsSnI3 (as HTL) with a thickness of 220 nm, a defect density of 5 × 1017 cm−3, and a doping density of 5 × 1019 cm−3 yielded the highest power conversion efficiency (PCE) of 23.90%. In addition, a 530 nm-FAPbI3 AL with a bandgap energy of 1.51 eV and a defect density of 1014 cm−3 was more favorable than MAPbI3 (1.55 eV) and CsPbI3 (1.73 eV) to attain a PCE of >24%. ML predicted the performance matrices of the investigated solar cells with ~75% accuracy. Therefore, the FTO/SnO2/FAPbI3/CsSnI3/Au structure would be suitable for experimental studies to fabricate high-performance photovoltaic devices.

Slot-Die-Coated Active Layer for Printed Flexible Back-Contact Perovskite Solar Cells

Perovskites have already shown potential as active layers in photovoltaic applications. Furthermore, a low-cost and simple solution processing technology allows perovskites to be used in flexible and printed electronics. Perovskite solar cells (PSC) with a back-contact (BC) structure, in which the electrode system is based on a quasi-interdigitated back-contact (QIBC) design, promise to increase the power conversion efficiency (PCE) of devices beyond those that can be obtained using PSCs with a traditional sandwich structure. While the spin-coating technique is used to deposit the perovskite layer of lab-scale BC PSCs, the application of large-area printing techniques to deposit the perovskite layer of such devices is yet to be explored. Therefore, this work demonstrates an application of the slot-die coating technique to print the perovskite active layer of BC PSCs with QIBC electrodes on flexible polymer substrates. The morphology of the obtained perovskite films on QIBC electrodes are investigated and the primary photoelectric parameters of the resulting BC PSCs are measured. The charge carrier recombination processes in the fabricated BC PSCs are investigated and the dominant mechanism for carrier loss in the devices is determined. The findings of the work give an insight into the properties of the slot-die-coated perovskite active layer of BC PSCs and points to exciting new research opportunities in this direction.

Functional Layers of Inverted Flexible Perovskite Solar Cells and Effective Technologies for Device Commercialization

Perovskite solar cells (PSCs) are now one of the most promising solar cells due to advantages such as high‐power conversion efficiency (PCE), low cost, and ease of fabrication. Among PSCs, flexible perovskite solar cells (FPSCs) are lightweight and bendable, making them easier to transport and install than rigid PSCs, and hence can be used in wearable and portable electronics, space energy systems, multifunctional integrated buildings, unmanned systems, and other applications. Compared with regular n–i–p FPSCs, inverted p–i–n FPSCs possess advantages of reliable operational stability, reduced hysteresis effect, low‐temperature fabrication process, and strong potential for tandem devices. At present, the PCEs of single‐junction and tandem‐inverted FPSCs have reached 21.76% and 24.7%, respectively, indicating promising commercial applications. In this review, first, the developments of device functional layers including flexible substrates, flexible conductive electrodes, charge transport layers, and perovskite active layers in inverted FPSCs are elucidated and discussed thoroughly. Then, the technologies for accelerating commercialization of inverted FPSCs are summarized in detail. Finally, perspectives on the development and commercialization of inverted FPSCs are provided.

Review on Enhancement of Stability and Efficiency of Perovskite Solar Cell

For photovoltaic applications, organic-inorganic hybrid perovskite solar cells have a extensive array of characteristics, including elevated absorption coefficients, exceptional carrier mobility, long charge carrier diffusion lengths, low cost, and incredible development. As emerging solar cell with thin film technology, these solar cells have generated many concerns. The elevated efficiency along with the low cost of materials and process are the main benefit of this cell over commercial silicon or other organic and inorganic solar cells. The foundations behind the optoelectronic description of perovskite materials and important methods for creating highly efficient perovskite solar cells have been covered in this paper. The degradation mechanisms of unstable perovskite materials and the associated solar cells are discussed. There are two more ways to increase the stability of perovskite materials and perovskite solar cells: interface engineering between the hole transport layer and the perovskite active layer and interface alteration between the electron transport layer and the perovskite layer. The future development of PSC architecture engineering is finally given a perspective and outlook.