Hybrid Halide Perovskite Solar Cells Research Articles

Modulation of Photoinduced Phase Segregation and Stress-Driven Nanoscale Cracking in Hybrid Halide Perovskite Solar Cells.

The negative effect of photoinduced halide segregation (PIHS) on the properties of hybrid halide perovskites poses a major obstacle for its future commercial application. Therefore, the in-depth understanding of halide-ion segregation and its causes is an urgent and intractable problem. When PIHS reaches a certain threshold, it will aggravate the deterioration of the film surface morphology and form nanoscale cracks. Herein, the formation mechanism and types of cracks are revealed by exploring the stress distribution in the film. Using the femtosecond time-resolved transient absorption spectroscopy, the ultrafast formation of the iodine rich phase is observed, which appears earlier than the bromine rich phase. In addition, the introduction of organic ligand didodecyldimethylammonium bromide can significantly inhibit PIHS and improve the surface morphology of the film, which can promote the device efficiency from 9.63 to 11.20%. This work provides a novel perspective for the exploration of the PIHS.

Ab-initio study of hybrid perovskites Cs2AgGaCl6 for solar cells applications

Double perovskites have garnered significant attention for use in renewable energy applications, particularly solar cells. The development of organic-inorganic hybrid halide perovskite solar cells has advanced rapidly over the last ten years. In this article, fundamental aspects of transport properties of Cs2AgGaCl6 have been illustrated using DFT-based simulation. Constantly is covered that the calculated lattice constant agreed with the available experimental data. With an indirect band gap, the electronic profile demonstrates a semiconducting nature. Reporting bandgap of 1.20 eV for Cs2AgGaCl6. This bandgap remains suitable for solar cell semiconductors. The computed values of effective masses reveal that effective masses of holes are greater than those of electrons. Further various optical parameters have also been examined. The absorption of light in the visible and ultraviolet spectrums is guaranteed by the absorption bands 2.7–4.2 eV and 3.5–4.5 eV. We believe that such insights offer a new starting point and a framework for future research. So, knowledge and drive gained from these studies will stimulate more theoretical investigation into novel perovskite-based materials with novel applications.

Improving the Conductivity of Amide-Based Small Molecules through Enhanced Molecular Packing and Their Application as Hole Transport Mediators in Perovskite Solar Cells.

Organic-inorganic hybrid halide perovskite solar cells (PSCs) have attracted substantial attention from the photovoltaic research community, with the power conversion efficiency (PCE) already exceeding 26%. Current state-of-the-art devices rely on Spiro-OMeTAD as the hole-transporting material (HTM); however, Spiro-OMeTAD is costly due to its complicated synthesis and expensive product purification, while its low conductivity ultimately limits the achievable device efficiency. In this work, we build upon our recently introduced family of low-cost amide-based small molecules and introduce a molecule (termed TPABT) that results in high conductivity values (∼10-5 S cm-1 upon addition of standard ionic additives), outperforming our previous amide-based material (EDOT-Amide-TPA, ∼10-6 S cm-1) while only costing an estimated $5/g. We ascribe the increased optoelectronic properties to favorable molecular packing, as shown by single-crystal X-ray diffraction, which results in close spacing between the triphenylamine blocks. This, in turn, results in a short hole-hopping distance between molecules and therefore good mobility and conductivity. In addition, TPABT exhibits a higher bandgap and is as a result more transparent in the visible range of the solar spectrum, leading to lower parasitic absorption losses than Spiro-OMeTAD, and has increased moisture stability. We applied the molecule in perovskite solar cells and obtained good efficiency values in the ∼15% range. Our approach shows that engineering better molecular packing may be the key to developing high-efficiency, low-cost HTMs for perovskite solar cells.

Approaching Full-Scale Passivation in Perovskite Solar Cells via Valent-Variable Carbazole Cations

Hybrid halide perovskite solar cells (PSCs) have emerged as the next-generation photovoltaic technology. Compared to steady silicon solar cells, PSCs are facilely processable but easily generate defects/traps during the thin-film fabrication from the solution. To passivate these defects, which have been considered as the origin of PSC instability, numerous large-sized organic cations (LSOCs) were applied via post-treatment methods. Unfortunately, along with the passivation on defects, these LSOCs could also react with regular perovskite phases and convert them into layered perovskite phases with poorer optoelectronic performances. Herein, we have designed carbazole ethylammonium iodide (CzEAI), a LSOC salt which exhibits a variation from monovalent to divalent state. Importantly, unlike traditional LSOC passivators in monovalent states mostly consumed by a regular perovskite phase and merely affecting the upper domain in thin films, CzEA in monovalent state could penetrate through the whole domain in perovskite films and then accurately convert into a divalent state at defect sites and thus realize a full-scale passivation in PSCs. Both simulation and experimental results proved that a CzEA passivator could overcome the formation of poor optoelectronic layered perovskite phases. As a result, the CzEA passivated PSC demonstrated an optimized photon-to-electron conversion efficiency (PCE) of 24.14% together with a significantly improved long-term stability over 5000 h.

Low-Temperature robust MAPbI3 perovskite solar cells with power conversion efficiency exceeding 22.4%

Hybrid halide perovskite solar cells (PSCs) have enormous potential to provide energy for future space exploration and aerospace due to their unique advantages in harsh environments. Unfortunately, it is challenging to fabricate robust PSCs that are insensitive to low temperatures. This study presented the performance evolution of methylammonium triiodide (MAPbI3) PSCs across a temperature range of 290 to 90 K and highlighted the decisive impact of interfacial defects on the devices’ low-temperature performance. The introduction of polymethyl methacrylate (PMMA) as interface modification layer, efficiently passivated the interface defects, released the interfacial stress, and thus decreased the phase transition temperature. As a result, the PMMA-modified device achieved a maximum efficiency of 22.4% at 90 K which was one of the highest efficiencies reported for MA-based PSCs at low temperatures. Remarkably, the PMMA-modified device retained nearly 100% of initial efficiency after 26 temperature cycling tests between 290 and 90 K, whereas the control device maintained only 62% of initial efficiency. This work demonstrated that interface engineering is a promising strategy for improving the low-temperature performance of PSCs.

Fluorinated 2-Phenylethylammonium Spacer Cations for Improved Stability of Ruddlesden–Popper Pb/Sn Halide Perovskites: Insight from First-Principles Calculations

Improving the stability of hybrid halide perovskite solar cells is essential for their commercialization in emerging cutting-edge technology. Here, we report the results of state-of-the-art first-principles calculations to achieve and understand enhancement in the stability of Ruddlesden–Popper (RP) lead/tin halide perovskites with fluorinated 2-phenylethylammonium (PEA) spacer cations. It is found that the substitution of up to five F atoms in the phenyl ring makes C slightly positively charged due to ∼0.5e charge transfer to electronegative F. This leads to the formation of electric dipoles in the spacer cation region and polarization of the charge density. This improves the formation energy and enhances the stability of the layers. The charge transfer makes some of the C 2p orbitals partly empty so that they hybridize with F 2p orbitals near the conduction band minimum. This is interesting for the charge transport perpendicular to the layers. Our study further shows that changing the metal cations Pb with Sn does not affect the orientation of the cation molecules in the pure as well as chemically tuned RP layers whereas changing the halide ions I with Br has an impact on the orientation of the organic molecules. The calculated structures of the layers agree well with the available experimental results and suggest structures of some unexplored layers that would be interesting to fabricate. The calculated electronic structure and optical properties show that the absorption coefficient is high (∼105 cm–1) for the layers having heavily fluorinated spacer cations. Furthermore, we find higher stability and a desirable lower direct band gap for Sn-based green perovskite layers compared to the Pb counterparts. Our results provide computational insight into the surface engineering of RP perovskites for further developments in this fast-growing area.

Innocuous hybrid-halide perovskite solar cells based on titania nanowires towards eco-friendly solar energy conversion

Innocuous hybrid-halide perovskite solar cells based on titania nanowires towards eco-friendly solar energy conversion

Enhanced efficiency and stability of perovskite solar cells based on carbon-counter-electrode via anti-solvent treatment

The quality of perovskite film seriously affects the performance of organic-inorganic hybrid halide perovskite solar cells. In this paper, we demonstrate an anti-solvent treatment by controlling the perovskite recrystallize to enhance the quality of perovskite film and photophysical properties, including crystallinity, high coverage and high absorption. The fabricated carbon-based perovskite solar cells show PCE improvement from 6.82% to 10.81% with less hysteresis, and remained 90% of the original value after 93 days in the air environment. Our work provides a way to prepare simple and stable perovskite devices with high stability and low cost. • The high-stability perovskite solar cells (PSCs) based on carbon electrode was fabricated under humidity air atmosphere. • The crystallization kinetics of perovskite was optimized by anti-solvent CB washing and high-quality films were prepared. • We investigated the effect of different dosage of CB the on PSCs. • The power conversion efficiency (PCE) of champion PSC was 10.81% with optimum dosage CB (100 μ L).

Enhancing the stability of planar perovskite solar cells by green and inexpensive cellulose acetate butyrate

Although the efficiency of organic–inorganic hybrid halide perovskite solar cells has been improved rapidly, the intrinsic instability of perovskite materials restricts their commercial application. Here, an eco-friendly and low-cost organic polymer, cellulose acetate butyrate (CAB), was introduced to the grain boundaries and surfaces of perovskite, resulting in a high-quality and low-defect perovskite film with a nearly tenfold improvement in carrier lifetime. More importantly, the CAB-treated perovskite films have a well-matched energy level with the charge transport layers, thus suppressing carrier nonradiative recombination and carrier accumulation. As a result, the optimized CAB-based device achieved a champion efficiency of 21.5% compared to the control device (18.2%). Since the ester group in CAB bonds with Pb in perovskite, and the H and O in the hydroxyl group bond with the I and organic cations in perovskite, respectively, it will contribute to superior stability under heat, high humidity, and light soaking conditions. After aging under 35% humidity (relative humidity, RH) for 3300 h, the optimized device can still maintain more than 90% of the initial efficiency; it can also retain more than 90% of the initial efficiency after aging at 65 °C, 65% RH, or light (AM 1.5G) for 500 h. This simple optimization strategy for perovskite stability could facilitate the commercial application of perovskite solar cells.

Structural evolution, dielectric relaxation, and charge transport characteristics of formamidinium lead iodide (FAPbI3) perovskite

Recently, hybrid halide perovskite solar cells have drawn the researchers’ attention, owing to their high-power conversion efficiency. Among the different compounds, MAPbI3 (MA = Methylammonium CH3NH3) and FAPbI3 (FA = Formamidinium CH(NH2)2) are especially potential candidates since their bandgap suited the energy range of visible light. Here, the hybrid perovskite FAPbI3 is successfully synthesized via the inverse temperature crystallization method. Different characterization techniques such as variable-temperature structural analyses, differential scanning calorimetry (DSC), and impedance spectroscopic analysis show that FAPbI3 presents a phase transition at T = 300 K from the hexagonal to the cubic symmetry. Optical analysis of FAPbI3 shows the direct band-gap value of ∼1.4 eV. FAPbI3 is characterized by impedance spectroscopy technique performed in the 10−1–106 Hz frequency and 210–390 K temperature ranges. The alternating current (AC) conductivity is illustrated in terms of Jonncher's power law. The study on charge transportation within FAPbI3 suggests the presence of the NSPT (non-overlapping small polaron tunneling) and OLPT (overlapping large polaron tunneling) models in the hexagonal and cubic phases, respectively.

Recent advances in lead-free based perovskite solar cells on optoelectronic properties, stability and economic feasibility

The present review article represents the scope of different lead (Pb)-free hybrid halide Perovskite solar cells (PSC) for photovoltaic (PV) applications. Research on lead-free material is emerging mainly to identify the alternatives of lead in the Perovskite solar cells. Several homovalent (Sn2+, Ge2+, Cu2+) and heterovalent (Sb3+, Bi3+, Ti4+) materials have good physical properties to replace the lead content in the absorbing material compound. However the power conversion efficiency (PCE, %) is not higher as compared to lead based material. This review article focuses on the characteristics, material properties, stability and performance of the different Pb-free materials as absorbing layer in the Perovskite solar cells.

Ultrathin Plasma Polymer Passivation of Perovskite Solar Cells for Improved Stability and Reproducibility

AbstractDespite the youthfulness of hybrid halide perovskite solar cells, their efficiencies are currently comparable to commercial silicon and have surpassed quantum‐dots solar cells. Yet, the scalability of these devices is a challenge due to their low reproducibility and stability under environmental conditions. However, the techniques reported to date to tackle such issues recurrently involve the use of solvent methods that would further complicate their transfer to industry. Herein a reliable alternative relaying in the implementation of an ultrathin plasma polymer as a passivation interface between the electron transport layer and the hybrid perovskite layer is presented. Such a nanoengineered interface provides solar devices with increased long‐term stability under ambient conditions. Thus, without involving any additional encapsulation step, the cells retain more than 80% of their efficiency after being exposed to the ambient atmosphere for more than 1000 h. Moreover, this plasma polymer passivation strategy significantly improves the coverage of the mesoporous scaffold by the perovskite layer, providing the solar cells with enhanced performance, with a champion efficiency of 19.2%, a remarkable value for Li‐free standard mesoporous n‐i‐p architectures, as well as significantly improved reproducibility.

One-step polymer assisted roll-to-roll gravure-printed perovskite solar cells without using anti-solvent bathing

High-throughput manufacturing of hybrid halide perovskite solar cells is the next challenge before they enter the market. An anti-solvent bath is generally required to control the perovskite film assembly starting from precursors in solution. Although an anti-solvent bath has proven feasible for roll-to-roll deposition, it implies an undoubted increased complexity of the manufacturing line, meaning enhanced costs for the process itself and anti-solvent disposal. Here, we take advantage of the use of a starch polymer as a rheological modifier in perovskite precursor solutions to avoid the anti-solvent bath. Starch allows for control of the perovskite growth process in one step and reach of required viscosities for gravure-printing technique with ∼50% less of the raw precursor materials. This combined with simplified processing conditions are expected to drastically lower the costs of perovskite material production. We demonstrate that this approach can be upscaled to roll-to-roll gravure printing of flexible solar cells, reaching a maximum power conversion efficiency close to 10%. Viscosity of perovskite-starch inks can be adapted to gravure printing requirements The viscosities required for gravure are reached with ∼50% less of the raw precursors Polymer endows perovskite with easy processability on a large area without anti-solvent bath Flexible solar cell fabricated by roll-to-roll processing with maximum PCE of ∼10% Bisconti et al. take advantage of a starch polymer as a rheological modifier in precursor solutions to deposit perovskite films in one step, avoiding the anti-solvent bath. Roll-to-roll gravure-printed perovskite films and flexible solar cells are demonstrated, reaching a maximum power conversion efficiency close to 10%.

In Situ Management of Ions Migration to Control Hysteresis Effect for Planar Heterojunction Perovskite Solar Cells

AbstractAs one of the most promising photovoltaic materials, the efficiency of inorganic–organic hybrid halide perovskite solar cells (PSCs) has reached 25.5% in 2020. However, the stability and hysteresis remain primary challenges before it can become a commercial photovoltaic technology. Therefore, those issues have drawn significant attention for photovoltaic applications. In this work, a study of the PSCs hysteresis improvement is presented based on a combination of first‐principles simulations, scanning electron microscopy images, and time‐dependent photocurrent measurements. It indicates the hysteresis led by the ion migration and accumulation is mainly localized at the two interfaces: one is between electron transport layer and active layer, and the other is between active layer and hole transport layer. Considering the massive defects at the grain boundaries (GBs), they lower the potential barriers significantly. The defect density at GBs is therefore reduced via the in situ passivation of PbI2 crystals. The hysteresis index is decreased from 22.43% down to 1.04%, and results in an improvement in efficiency from 17.12% up to 20.10%. Following the understanding of defect‐induced hysteresis, an approach to improve the hysteresis is provided, which can be integrated into the fabrication process and widely applied to enhance the performance of PSCs.

Elastic Lattice and Excess Charge Carrier Manipulation in 1D-3D Perovskite Solar Cells for Exceptionally Long-Term Operational Stability.

3D organic-inorganic hybrid halide perovskite solar cells (pero-SCs) inherently face severe instability issue due to ion migration under operational conditions. This ion migration inevitably results from the decomposition of ionic bonds under lattice strain and is accelerated by the existence of excess charge carriers. In this study, a 1D-3D mixed-dimensional perovskite material is explored by adding an organic salt with a bulk benzimidazole cation (Bn+ ). The Bn+ can induce 3D perovskite crystalline growth with the preferred orientation and form a 1D BnPbI3 perovskite spatially distributed in the 3D perovskite film. For the first time, the electro-strictive response, which has a significant influence on the lattice strain under an electric field, is observed in polycrystalline perovskite. The 1D-3D perovskite can effectively suppress electro-strictive responses and unbalanced charge carrier extraction, providing an intrinsically stable lattice with enhanced ionic bonds and fewer excess charge carriers. As a result, the ion migration behavior of the p-i-n 1D-3D based pero-SC is dramatically suppressed under operational conditions, showing ultra-long-term stability that retains 95.3% of its initial power conversion efficiency (PCE) under operation for 3072 h, and simultaneously achieving an excellent PCE with a hysteresis-free photovoltaic behavior.

Study of defects in CH3NH3PbI3-based perovskite solar cells

The present work will focus on the investigation of the influence of defects density and carriers capture cross-section are in absorption layer on the performance of perovskite solar cells. Furthermore, the impact of defect density in the electron transport material ETM/absorber interface layer will also be studied. The hybrid halide perovskite solar cells are chosen in this work and will be simulated by using one-dimension solar cells capacitance simulation SCAPS-1D. The proposed structure of the perovskite solar cell is a planar FTO/ETM/perovskite/HTM based on TiO2 and Spiro-OMeTAD as electron transport layer ETM and hole transport layer HTM, respectively, and on CH 3NH 3PbI 3 as absorber layer (perovskite). The results showed that when the defect density in the absorber layer was varied from 10 10cm -3 to 10 18 cm -3, the cell parameters, open circuit voltage (V oc), the short circuit current (J sc ), the fill factor (FF), and the efficiency (PCE)were significantly decreased. At high defect density (10 18 cm -3), the defect affects negatively on the cell performance due to the high recombination rate of Shockley Read Hall. Similarly, the capture cross section exhibits similar behaviour in the active layer. By increasing the defect density in the ETM/absorber interface layer, the main cell parameters PCE, FF, and J sc are slightly reduced and there has been no noticeable impact on V oc .

Confined Growth of High-quality Single-Crystal MAPbBr3 by Inverse Temperature Crystallization for Photovoltaic Applications

Organic–inorganic hybrid halide perovskite solar cells are promising for next-generation thin-film solar cells, demonstrating power conversion efficiency exceeding 25%. In particular, single-crystal perovskite materials are estimated to possess superior optoelectronic properties that can further enhance the efficiency. However, fabricating thin single-crystal perovskite for a light-absorber layer remains challenging. In this study, a 40-µm-thick single-crystalline MAPbBr3 perovskite is fabricated by inverse temperature crystallization (ITC) with a selective seed-transfer technique. By using a separate seed growth process and a seed-transfer process, a 16.23-mm2-large single domain high-quality single-crystalline MAPbBr3 perovskite can be grown without additional nucleation. The grown single-crystal MAPbBr3 exhibits a low surface roughness of 0.51 nm and low trap density of 7.61 × 108 cm−3. We also fabricate solar cells with single-crystalline MAPbBr3 using a glass substrate coated with SnO2 and indium-tin-oxide thin films. The single-crystal MAPbBr3-based solar cells demonstrate a power conversion efficiency of 4.31%.

Temperature‐ and Bias‐Dependent Degradation and Regeneration of Perovskite Solar Cells with Organic and Inorganic Hole Transport Layers

Hybrid halide perovskite solar cells have drawn widespread attention with the achievement of high power conversion efficiencies. However, poor stability remains the greatest barrier preventing their commercialization. Performance degradation and recovery have a complicated dependence on the environment and a dependence on the applied bias, which affects ion migration. Herein, solar cells with an organic hole transport layer and cells with an inorganic hole transport layer are compared. A type of degradation of the organic transport layer is examined, which is reversible by applying a forward bias soak, and how the degradation arises from ion migration mechanisms is explained. Experimental current–voltage and capacitance transient measurements are conducted as a function of temperature. The resulting S‐kink and positive capacitance decay are explained in terms of the modeled effects of a changing ion density at the hole transport layer. An irreversible degradation is found upon heating to more than 100 °C. On the contrary, the inorganic hole transport layer is found to eliminate the observable effects of ion migration, even at elevated temperatures, so long as air exposure is avoided.

First-principles identification of the charge-shifting mechanism and ferroelectricity in hybrid halide perovskites

Hybrid halide perovskite solar cells have recently attracted substantial attention, mainly because of their high power conversion efficiency. Among diverse variants, (CH3NH3)PbI3 and HC(NH2)2PbI3 are particularly promising candidates because their bandgap well matches the energy range of visible light. Here, we demonstrate that the large nonlinear photocurrent in β-(CH3NH3)PbI3 and α-HC(NH2)2PbI3 is mostly determined by the intrinsic electronic band properties near the Fermi level, rooted in the inorganic backbone, whereas the ferroelectric polarization of the hybrid halide perovskite is largely dominated by the ionic contribution of the molecular cation. The spatial charge shift upon excitation is attributed to the charge transfer from iodine to lead atoms in the backbone, which is independent of the presence of the cationic molecules. Our findings can serve as a guiding principle for the design of future materials for halide-perovskite solar cells with further enhanced photovoltaic performance.

Surfactant Sodium Dodecyl Benzene Sulfonate Improves the Efficiency and Stability of Air‐Processed Perovskite Solar Cells with Negligible Hysteresis

The device performance of organic–inorganic hybrid halide perovskite solar cells (PSCs) is highly dependent on the quality of perovskite layer. Herein, a multifunctional chemical additive strategy is reported to simultaneously improve the efficiency and stability of fully air‐processed PSCs. The planner methylammonium lead trihalide (MAPbI3)‐based PSCs incorporating sodium dodecyl benzene sulfonate (SDBS) exhibit a champion power conversion efficiency (PCE) of 19.20% and negligible hysteresis, which is one of the top efficiencies of MAPbI3‐based PSCs made in air. The increased efficiency is due to the reduction of defects and inhibition of ion migration in the perovskite films. Furthermore, the enhancement of device performance and stability can also be ascribed to highly preferred and efficient perovskite crystals protecting the perovskite films from humidity. The corresponding unencapsulated device retains 92.34% of its initial efficiency after 90 days (>2100 h) storage in air and maintains 85.20% of its original PCE after being exposed to 85 °C for 27 h. The results indicate that SDBS is a promising chemical additive to enhance the performance of air‐processed PSCs for future applications.