Planar Perovskite Solar Cells Research Articles

Solar absorptivity analysis of nanostructure perovskite solar cell

Perovskite solar cell is a promising alternative to silicon solar cells; it is cheaper and more environmentally friendly to fabricate with comparable power conversion efficiency. This research investigated the enhancement of the solar absorptivity of a planar structure perovskite solar cell by implementing various nanostructures. Four different glass nanostructure architectures, including nanocone, nanopyramid, nanotube, and nanorod placed at the initial top layer of the cell, were simulated using the three-dimensional finite element method. We studied the effects of nanostructure architecture's varying height and domain area on solar absorptivity. The result showed that the tapered shapes had higher solar absorptivity with increased height. The nanocone with a domain area of 300 nm × 300 nm at the tallest height of 200 nm had the most significant solar absorptivity enhancement with 407 W/m2 of integrated irradiance, 3.3% higher compared to the planar structure. In addition, the analysis of integrated irradiance using AM 1.5 G of different nanocone domain areas revealed various local maxima and minima. These findings suggest an alternative design option to increase efficiency without texturing the active perovskite cell layer.

Enhancing Planar Perovskite Solar Cell Performance by SnO2 Interface Treatment Using Urea as an Additive: A Comparative Study of Simple, Low-Temperature Approaches

Enhancing Planar Perovskite Solar Cell Performance by SnO₂ Interface Treatment Using Urea as an Additive: A Comparative Study of Simple, Low-Temperature Approaches

Amino-rich carbon quantum dots decorated SnO2 ETL with enhanced charge extraction for efficient perovskite solar cells

An electron transport layer (ETL) with excellent conductivity and charge extraction ability plays a vital role in accelerating charge extraction and transportation for achieving highly efficient planar perovskite solar cells (PSCs). Herein, amino-rich carbon quantum dots (shortened as ACDs hereafter) with multi-roles are developed and introduced into SnO2 precursor solution to enhance the photoelectric properties of SnO2. First, the conductivity and the Fermi energy level of SnO2 are improved via electron injection from ACDs. With the help of ACDs, the conductivity of SnO2:ACDs is increased from 2.77 × 10−2 mS/cm2 to 6.56 × 10−2 mS/cm2 under illumination, which contribute to efficient charge transport and collection within PSC device. Secondly, the amino functional groups on the surface of ACDs promote the saturated growth of perovskite grain, forming high-quality photoactive layers. When deposited on the SnO2:ACDs, the average gain size of perovskite film is increased from 0.86 μm to 1.1 μm. These outstanding properties greatly accelerate the charge extraction and reduce the trap density within the perovskite layer. As a result, the PSC with ACDs exhibit a champion efficiency of 22.02 % compared with 20.33 % of the control device, and the device stability is also significantly improved.

Effect of addition of indium oxide layer on all-inorganic perovskite solar cells

In perovskite solar cells, the interface plays a crucial role in photovoltaic performance because excitons dissociate and compound at the interface. In this paper, the optical absorption layer of In2O3 planar perovskite solar cells is studied, which is an efficient intermediate layer between the TiO2 electron transport layer and perovskite. The modification of the In2O3 interlayer increases the average power conversion efficiency from 6.74% to 10.68%. Based on this background, some other feature descriptions are also carried out. The results show that the photovoltaic performance can be improved by depositing the In2O3 interlayer, mainly due to the improved film morphology, reduced recombination center, bulk carrier concentration and Hall mobility. It has been shown that In2O3 can be used as an efficient interface material on all-inorganic perovskite solar cells.

Spiro-OMeTAD doped with iodine pentoxide to enhance planar perovskite solar cell performance

Due to its enormous development potential, research on perovskite solar cells (PSCs) is progressing rapidly worldwide. Among numerous hole transport materials (HTMs), an organic molecule spiro-OMeTAD emerged victorious. Spiro's application in PSCs is constrained to its weak hole mobility and low conductivity. Here, an inexpensive, ecologically friendly inorganic oxidant iodine pentoxide (I2O5) is used to aid in quick and manageable oxidation of Spiro. I2O5-modified Spiro as HTM improves the charge carrier transportation. Meanwhile, trap-states density and trap-assisted recombination are decreased. Additionally, the modification adjusts the HTM's energy level to match the perovskite layer properly. As a result, the I2O5-modified PSC achieves a champion power conversion efficiency of 22.80%, while the pristine device gets an efficiency of 20.65%.

Multifunctional Polymer Restraint of the Agglomeration of SnO2 Nanocrystals for Efficient and Stable Planar Perovskite Solar Cells.

The aggregation of SnO2 nanocrystals due to van der Waals interactions is not conducive to the realization of a compact and pinhole-free electron transport layer (ETL). Herein, we have utilized potassium alginate (PA) to self-assemble SnO2 nanocrystals, forming a PA-SnO2 ETL for perovskite solar cells (PSCs). Through density functional theory (DFT) calculations, PA can be effectively absorbed onto the surface of SnO2. This inhibits the agglomeration of SnO2 nanocrystals in solution, forming a smoother pinhole-free film. This also changes the surface contact potential (CPD) of the SnO2 film, which leads to a reduction in the energy barrier between the ETL and the perovskite layers, promotes effective charge transfer, and reduces trap density. Consequently, the power conversion efficiency (PCE) of PSCs with a PA-SnO2 ETL increased from 19.24% to 22.16%, and the short-circuit current (JSC) was enhanced from 23.52 to 25.21 mA cm-2. Furthermore, the PA-modified unpackaged device demonstrates better humidity stability compared to the original device.

Interface Modification Using Li-Doped Hollow Titania Nanospheres for High-Performance Planar Perovskite Solar Cells.

Titania nanospheres have been utilized as building blocks of electron transporting layers (ETLs) for mesoscopic perovskite solar cells (PSCs). Nevertheless, the power conversion efficiencies (PCEs) reported so far for the mesoscopic PSCs containing titania nanospheres are generally lower than those of the state-of-the-art planar PSCs. Here, we have prepared Li-doped hollow titania nanospheres (Li-HTS) through a "cation-exchange" approach and used them for the first time to modify the SnO2 ETL/perovskite interfaces of planar PSCs. The Li-HTS-modified PSC delivered a PCE of 23.28% with a fill factor (FF) of over 80%, which is significantly higher than the PCE of the control device (20.51%). This is the best PCE achieved for PSCs containing titania nanospheres. Moreover, interfacial modification using Li-HTS greatly improves the stability of the PSCs. This work demonstrates the potential of interface modification using inorganic nanostructures for enhancing the efficiency and stability of planar PSCs.

Review on Surface Modification of SnO2 Electron Transport Layer for High-Efficiency Perovskite Solar Cells

In the planar heterojunction perovskite solar cell (PSC) structure, among numerous contenders, tin oxide (SnO2) has been utilized, instead of TiO2, as the material for the electron transport layer (ETL) owing to its good band alignment, ultraviolet light resistance, strong charge extraction, and low photocatalytic activity. However, the morphology of the SnO2 ETL has proven to be unstable under low-temperature processing, leading to low electron extraction in PSCs. Therefore, the surface morphology must be modified to achieve high-performance PSCs. In this review, we provide an overview of the fundamental insights into how surface variations affect the ETL performance. The significance and the design rule of surface modification for an efficient SnO2 ETL, that is, the intentional alteration of the SnO2 interface, are discussed. Based on the evaluations, distinct surface engineering procedures and how they are implemented are presented. The effects of chemical and physical interactions on the properties of SnO2 are elucidated in detail; these have not been considered in previous studies. Finally, we provide an outlook on, highlight the key challenges in, and recommend future research directions for the design of the interfaces of highly efficient and stable PSCs.

Octylammonium Iodide Induced In-situ Healing at "perovskite/Carbon" Interface to Achieve 85% RH-moisture Stable, Hole-Conductor-Free Perovskite Solar Cells with Power Conversion Efficiency >19.

"Perovskite/carbon" interface is a bottle-neck for hole-conductor-free, carbon-electrode basing perovskite solar cells due to the energy mismatch and concentrated defects. In this article, in-situ healing strategy is proposed by doping octylammonium iodide into carbon paste that used to prepare carbon-electrode on perovskite layer. This strategy is found to strengthen interfacial contact and reduce interfacial defects on one hand, and slightly elevate the work function of the carbon-electrode on other hand. Due to this effect, charge extraction is accelerated, while recombination is obviously reduced. Accordingly, power conversion efficiency of the hole-conductor-free, planar perovskite solar cells is upgraded by ≈50%, or from 11.65 (± 1.59) % to 17.97 (± 0.32) % (AM1.5G, 100mWcm-2 ). The optimized device shows efficiency of 19.42% and open-circuit voltage of 1.11V. Meanwhile, moisture-stability is tested by keeping the unsealed devices in closed chamber with relative humidity of 85%. The "in-situ healing" strategy helps to obtain T80 time of >450h for the carbon-electrode basing devices, which is four times of the reference ones. Thus, a kind of "internal encapsulation effect" has also been reached. The "in situ healing" strategy facilitates the fabrication of efficient and stable hole-conductor-free devices basing on carbon-electrode.

Design of fullerene-based interface passivation coatings for n-i-p perovskite solar cells: Addend size matters!

Perovskite solar cells (PSCs) have gained much attention because of their impressive power conversion efficiency (PCE) of up to 25.5%. Currently, low-temperature-processed SnO2 thin films are widely used as the ETLs to achieve efficient and stable planar PSCs. Surface passivation of SnO2 as electron transport layer (ETL) by fullerene derivatives is known as one of the ways to enhance the performance of n–i–p devices. Herein, we report a synthesis of new fullerene derivatives with hydroxyl and carboxyl functional groups, which are expected to contribute to more efficient modification of SnO2 surface. A comparative study of five fullerene derivatives as passivation layers allowed to establish the correlation between the molecular formula and performance of PSCs. Moreover, optimized passivation interlayers of monocyclopropanated fullerene derivative with carboxylic group improved the efficiency of perovskite solar cells in compare with conventional PCBA from 17.0% to 19.5%. This study highlights the key role of molecular design in passivation of SnO2 for pursuing high performance PSCs with n-i-p configuration.

Recent Advances of Doped SnO2 as Electron Transport Layer for High-Performance Perovskite Solar Cells.

Perovskite solar cells (PSCs) have garnered considerable attention over the past decade owing to their low cost and proven high power conversion efficiency of over 25%. In the planar heterojunction PSC structure, tin oxide was utilized as a substitute material for the TiO2 electron transport layer (ETL) owing to its similar physical properties and high mobility, which is suitable for electron mining. Nevertheless, the defects and morphology significantly changed the performance of SnO2 according to the different deposition techniques, resulting in the poor performance of PSCs. In this review, we provide a comprehensive insight into the factors that specifically influence the ETL in PSC. The properties of the SnO2 materials are briefly introduced. In particular, the general operating principles, as well as the suitability level of doping in SnO2, are elucidated along with the details of the obtained results. Subsequently, the potential for doping is evaluated from the obtained results to achieve better results in PSCs. This review aims to provide a systematic and comprehensive understanding of the effects of different types of doping on the performance of ETL SnO2 and potentially instigate further development of PSCs with an extension to SnO2-based PSCs.

NH4PF6 assisted buried interface defect passivation for planar perovskite solar cells with efficiency exceeding 21%

NH4PF6 assisted buried interface defect passivation for planar perovskite solar cells with efficiency exceeding 21%

SnO2:TiO2 hybrid nanocrystals as electron transport layer for high-efficiency and stable planar perovskite solar cells

SnO2:TiO2 hybrid nanocrystals as electron transport layer for high-efficiency and stable planar perovskite solar cells

Rapid 2D Patterning of High‐Performance Perovskites Using Large Area Flexography

AbstractSolution processing of metal halide perovskites offers the potential for efficient, high‐speed roll‐based manufacturing of emerging optoelectronic devices such as lightweight photovoltaics and light emitting diodes at lower cost than achievable with incumbent technologies (e.g., Silicon). However, current perovskite fabrication methods are limited in their speed, uniformity, and patterning resolution, relying on subtractive postdeposition scribing for integration of modules and device arrays. Here, a method for flexographic printing of MA0.6FA0.4PbI3 at 60 m min−1, the fastest reported perovskite absorber deposition and the first report of inline drying integrated with roll‐based printing, is presented. This process delivers high‐resolution patterning (< 3 µm line edge roughness) and precise thickness control through rheological design of precursor inks, allowing scalably printed 50 µm features over large areas (140 cm2), while obviating damaging scribing steps. 2D scanning photoluminescence (PL) is applied to resolve correlations between ink leveling dynamics and optoelectronic quality. Integrating these highly uniform printed perovskite absorbers into n‐i‐p planar perovskite solar cells, photovoltaic conversion efficiency up to 20.4% (0.134 cm2), the highest performance yet reported for any roll‐printed perovskite cells is achieved. This study, thus, establishes flexography as a scalable approach to deposit precisely‐patterned high‐quality perovskites extensible to applications in emitter and detector arrays.

Design and optimization of non-toxic and highly efficient tin-based organic perovskite solar cells by device simulation

An organic, lead-free, n-i-p planar perovskite solar cell (PSC) based on CH3NH3SnI3 was demonstrated in this work using a solar cell capacitance simulator (SCAPS). A material cell design of FTO/ZnO/CH3NH3SnI3/Cu2O/Au has been investigated for this study. A detailed analysis has been performed on the role of thickness, electron affinity, doping concentration of the perovskite layer, ETL, HTL, defect density of perovskite layer and temperature on PSC performance. For optimum conditions, the energy conversion efficiency is around 26.55%, accompanied by fill factor = 85.58%, open circuit voltage = 1.03 V, short circuit current density = 30.14 mA/cm2, and quantum efficiency of 80%–90%. This model shows the prospect of CH3NH3SnI3 as a perovskite material to produce toxic-free environment-friendly solar cells with high efficiency.

Highly efficient and durable planar carbon-based perovskite solar cells enabled by polystyrene modified hole-transporting layers

The efficiency and durability of perovskite solar cells (PSCs) are closely related to the property and stability of each functional layer involved in device. Owing to the excellent hole transport properties, the additive-doped Spiro-OMeTAD (2,2′,7,7′-tetrakis (N,N-di-p-methoxyphenylamine) 9,9′-spirobifluorene) has become an excellent hole-transporting material for obtaining highly efficient PSCs. However, the hygroscopic nature of additives and the pinholes caused by poor film-forming capability inevitably impair the performance and long-term stability of Spiro-OMeTAD and the resulting PSCs. In this study, the hydrophobic polymer polystyrene (PS) was incorporated to improve the hydrophobicity and film-forming capability of the additive-doped Spiro-OMeTAD films. Based on the PS-modified Spiro-OMeTAD and carbon electrodes, the derived planar carbon-based PSCs exhibited significantly enhanced long-term stability, which can maintain 92% of its initial efficiency after aging for 2500 h under ambient atmosphere without encapsulation. In addition, the PS-modified Spiro-OMeTAD exhibited improved morphology with reduced pinholes, contributing to significantly enhanced interfacial carrier transport. Finally, a champion power conversion efficiency of 21.06% was obtained, which is one of the highest efficiencies reported for the planar carbon-based PSCs to date.

Roller Nanoimprinted Honeycomb Texture as an Efficient Antireflective Coating for Perovskite Solar Cells

AbstractThe properly chosen light management strategy in perovskite solar cell devices is indispensable in achieving high power conversion efficiency. To diminish the reflection losses, texturization of the front surface, similar to what is used in established solar cell technologies, shall be taken into consideration. Within this paper, a honeycomb‐like textured SU‐8 photoresist layer is applied using a roller nanoimprint technique onto a planar perovskite solar cell to minimize reflection losses. The results show that the applied honeycomb pattern reduces the solar‐weighted reflectance from 13.6% to 2.7%, which enhances the current density of the unmodified cell by 2.1 mA cm−2, outperforming the commonly used planar MgF2 antireflective coating by 0.5 mA cm−2. The experimental results are combined with optical modeling to find optimized structures and predict the optical behavior within a solar module. The process used within this work can be transferred to perovskite‐silicon tandem solar cells, providing a promising pathway for the reflection reduction in future devices.

Preparation of Zn2+ doped NiCo2O4: Hole transport layer for high performance of perovskite solar cells

Inorganic hole transport materials (HTMs) play an important role for the stability and efficiency of planar perovskite solar cells (PSCs). Among the numerous inorganic HTMs, NiCo2O4 with its excellent performance is the emerging candidate for hole transport layers (HTLs) and is attracting increasing attention. However, the low electrical conductivity and optical transmittance of NiCo2O4 severely limit the device performance. Herein, the Zn2+ was used to dope NiCo2O4 to improve the electrical conductivity and optical transmittance of NiCo2O4. And the effects of the concentration of Zn2+ on the morphology, structure and properties of NiCo2O4 were investigated. The morphology and transparency of ZnxNi1-xCo2O4 would not be affected when the concentration of Zn2+ is below 0.1, but when it is up to 0.15 and 0.2, the morphology of NiCo2O4 clustered together or showed a diamond-shaped block, and the optical transmittance also decreased significantly. Meanwhile, with the increase of doping amount, the conductivity and hole mobility are gradually increased. As a result, the optimal concentration of Zn2+ is 0.1. Besides, the Zn0.1Ni0.9Co2O4 possessed a significant improvement in hole extraction and better band alignment compared to the NiCo2O4. And hence, the power conversion efficiency (PCE) of PSCs fabricated in open air is up to 13.41% by using Zn0.1Ni0.9Co2O4. This work develops a potential strategy for developing highly efficient and stable PSCs, opens up a new horizon for the development of inorganic HTMs.

Characterization of perovskite films prepared with different PbI2 deposition rates

The perovskite (CH3NH3PbI3) films prepared using PbI2 film deposited at controlled deposition rates were evaluated. In this process, PbI2 films were deposited by vacuum evaporation process and then converted into CH3NH3PbI3 films by annealing in methylammonium iodide vapor. The grain size of CH3NH3PbI3 films were successfully tuned from 90 to 125 nm by controlling the PbI2 deposition rate from 0.025 to 0.4 nm s−1. Furthermore, by using the controlled CH3NH3PbI3 film as the light harvesting layer, inverted planar perovskite solar cells were fabricated, and the improvement in power conversion efficiency was confirmed.

Regulating molecular stacking to construct a superior interfacial contact for highly efficient and stable perovskite solar cells

The non-radiative charge carrier recombination loss at the surface and interface of the perovskite layers in perovskite solar cells (PSCs) is the main cause of their limited power conversion efficiency (PCE). Here we propose an efficient strategy to minimize the non-radiative recombination by introducing symmetric molecules with regular arrangement at the interface between the perovskite layer and hole transport layer (HTL). One end of the symmetric molecule gets in a close contact with the terminal groups of the molecules in the HTL, while the other end promotes connection with the perovskite, resulting in an enhanced interfacial electrical contact and a better valence band energy-level alignment for efficient hole extraction. In contrast, introducing similar but asymmetrical molecules forms a dimer structure and mismatched energy levels at the interface region, which is detrimental to the carrier transport. The best-performing planar PSC with the symmetric molecular modification exhibited an increase in the PCE from 21.05% to 24.02% with a substantially enhanced fill factor of 84.0%, which can be ascribed to the synergistic effects of surface defect passivation and reduction in the interfacial energy barrier. Furthermore, the corresponding unencapsulated PSC retained 80% of the original PCE after 4,000 h of aging in dry air.