Enhancing the Performance and Photostability of Perovskite Solar Cells with a Multifunctional Light‐Management Composite

Lead-free tin perovskite solar cells

ABX<sub>3</sub> crystalline perovskite material has many advantages: good photoelectric absorption property, high charge carrier mobility, good film formation, long charge carrier lifetime, and easy bandgap adjustment for absorption layer of perovskite solar cells. As a result, the power conversion efficiency (PCE) of the organic-inorganic halide perovskite solar cells (PSCs) has taken a tremendous step forward, from 3.9% in 2009 to a recently reported value over 25.5%. Thus, it shows great potential to compete with traditional silicon solar cells. However, PSCs preparing conditions are harsh and susceptible to environmental influences, thus leading to instability. Therefore, it is essential to prepare high-performance and stable PSCs in an air environment. This study aims to use the ion doping method to improve the performance and stability of PSCs and analyze the mechanism. This work focuses on enhancing PSCs efficiency and stability by performing FA<sup>+</sup> and Cl<sup>–</sup> doping experiments on MAPbI<sub>3</sub> films in air. The results show that a single Cl<sup>–</sup>-doping increases the carrier diffusion length, reducing the recombination of electrons and holes, and inducing the perovskite intermediate hydrate (CH<sub>3</sub>NH<sub>3</sub>)<sub>4</sub>PbI<sub>6</sub>·2H<sub>2</sub>O to form, promoting the crystallization of the thin film, and improving the device performance. On the other hand, a single FA<sup>+</sup>-doping will reduce the bandgap of perovskite and increase the short-circuit current density (<i>J</i><sub>SC</sub>) of the device, and FA<sup>+</sup> is susceptible to the influence of water vapor to induce a yellow <i>δ</i>-FAPbI<sub>3</sub> perovskite film to form, which leads the device performance to degrade. However, the prepared co-doping Cl<sup>–</sup>, FA<sup>+</sup> significantly improves overall PSCs device performance, yielding the highest PCE of 17.29%, and showing excellent stability by maintaining over 80% of the original PCE without any encapsulation after 1000-hour storage in ambient air.

SnO2 is a widely used electron‐transporting layer (ETL) in perovskite solar cells. Despite the high compatibility with the perovskite absorber layers, the presence of traps at the perovskite|SnO2 interface results in performance losses; hence, their modification to improve the performance and stability of perovskite solar cells (PSCs) is therefore important. Herein, the SnO2 ETL is enhanced by incorporating a bifunctional aromatic amino fluorine molecule into the SnO2 precursor solution. The fluorine molecule is found to partially substitute the Sn and alter the energy levels while the aniline group aids in regulating the nucleation/growth rate of the perovskite crystalline films. Herein, a hole transporting material‐free carbon‐based PSCs (CPSCs) is fabricated. It is found that perovskite absorber layers deposited on these modified SnO2 hybrid layers have higher optoelectronic quality, resulting in enhanced photovoltaic performance, device stability, and reduced hysteresis in CPSCs. Devices made with the modified hybrid SnO2 layers exhibit power conversion efficiencies of 15.6% significantly better than unmodified SnO2 with 13.5%. CPSCs with these modified SnO2 films also exhibit remarkable retention of 88.7% of their initial PCE for a shelf‐life period (ISOS‐D1I) exceeding 1200 h.

Organometal hybrid perovskite material has emerged as an attractive competitor in the field of photovoltaics due to its promising potential of low-cost and high-efficiency photovoltaic applications. Although organometal halide perovskite solar cell shows great potential to meet future energy needs, the degradation raises serious questions about its commercialization viability. At present, the stability of perovskite solar cells has been studied in various environmental conditions. Nonetheless, an understanding of the degradation and its performance of CH3NH3PbI3-xClx perovskite solar cell is limited. Herein, we report the mechanical and structural degradation of CH3NH3PbI3-xClx perovskite films at room temperature as a function of time and thermal instability of perovskite solar cells during the heating and cooling processes. For mechanical degradation measurement, we used nanoindentation for CH3NH3PbI3-xClx perovskite films fabricated on FTO/PEDOT:PSS substrate. The hardness and elastic modulus of perovskite films were measured as a function of time. In addition, the mechanical degradation of perovskite thin films was correlated with X-ray diffraction, steady-state and time-resolved photoluminescence (PL). We also investigated the thermal instability of perovskite thin films and the irreversible performance of perovskite solar cells. Particularly, the irreversible performance of CH3NH3PbI3-xClx was analyzed by measuring the development of crystallinity, charge trapping/detrapping, trap depth, and PbI- phase while varying the temperature of perovskite films and solar cells between room temperature and 82 °C. Surprisingly, we found that the degradation of both perovskite films and solar cells occurred at ~70°C. Remarkably, even after the perovskite solar cell temperature cooled down to room temperature, the performance of solar cells continuously degraded. The underlying mechanism of irreversibly degraded performance of perovskite films and solar cells were explained in terms of the development of phase separation, increased trapping rates and deep trap depth of defect states of perovskite films.

Decoupling the effects of defects on efficiency and stability through phosphonates in stable halide perovskite solar cells

RF sputtered CdS films as independent or buffered electron transport layer for efficient planar perovskite solar cell

Perovskite solar cells (PSCs) have emerged as a promising technology for renewable energy generation due to their low cost and low carbon footprint compared to traditional silicon-based solar cells. However, some main challenges associated with PSCs lie ahead, namely their toxicity and lack of stability, particularly under factors such as light, temperature, oxygen, and humidity. We focus on the lack of stability of PSCs and the various ways it can be mitigated. We explore the use of vapor deposition methods, which can increase the crystallinity of the perovskite and thus improve stability and lifetime. Furthermore, we look into the potential of ionic liquids (ILs) as promising materials for improving the stability and performance of PSCs. ILs have advantageous physicochemical properties that make them suitable as an additive or interfacial layer in PSCs. They optimize the interface contact, improve energy level matching, suppress ion migration, and increase hydrophobicity, which inhibits the decomposition of the device in humid environments. ILs have also been used as precursors in the solution-based fabrication of perovskite thin films for PSC applications, assisting in the perovskite crystallization. Several studies have shown that the incorporation of ILs in PSCs can increase stability, lifetime, and efficiency. Overall, the existing research indicates that ILs hold great promise as materials for improving the stability and performance of PSCs, which could have significant implications for the development of low-cost, renewable energy technologies.

Hybrid organic-inorganic tin (Sn)-based perovskite materials became a promising choice as an alternative to lead-free perovskite solar cells (PSCs) due to their outstanding optical and electrical properties. But, so far, a power conversion efficiency (PCE) of only 13% has been achieved for Sn-based PSCs. To achieve highly efficient and stable PSCs, not only the properties of the active layer but the charge selective contacts (electron and hole transport layers) should be selected wisely. The interfaces between the perovskite active layer and charge transport layers play an important role in achieving the better performance of PSCs. In the present review, the spotlight is on the recent developments made on the optimization of electron transport layers (ETLs) for the efficient Sn-based hybrid organic-inorganic PSCs. Further, we comprehensively discuss the significance and the impact of the lowest unoccupied molecular orbital level of electron transport material on the charge transport, which additionally affects the photovoltaic performance of the device. In summary, with continuous research on the Sn-based hybrid organic-inorganic perovskite materials as an absorbing layer, conventional ETLs (metal oxides) cannot be used. Thus, the optimum candidate for befitted ETLs must be explored and investigated in detail for efficient PSCs.

Organic–inorganic hybrid perovskite solar cells (PSCs) attract many researchers in the field of photovoltaic because of their high‐power conversion efficiency and low‐cost manufacturing. However, improper interfacial charge transfer, perovskite degradation, and poor stability are major concerns for their commercialization and scale‐up. Significant efforts have been made in recent years mainly by employing different strategies such as optimizing fabrication, developing novel materials, use of additives, and an interfacial layer in PSCs. Nowadays, carbon materials are widely recognized as promising candidates for alternative usage in PSCs because of their cost effectiveness, high conductivity, appropriate work function (5.0 eV), and low‐temperature sintering process. In addition, the highly hydrophobic nature of the carbon‐based materials prevents moisture penetration into the perovskite layer, resulting in enhanced stability. This review shows how effectively carbon‐based materials can improve the performance of PSCs. First, the different carbon materials such as graphene and its derivatives, fullerenes and its derivatives, carbon quantum dots, and carbon nanotubes are described. Subsequently, the role of these carbon‐based materials employed in electron‐transport layers, hole‐transport layers, and perovskite layers in PSCs is discussed. Thus, this review highlights the recent advancements made in carbon‐based PSCs and their role in improving the performance of PSCs.

Morphology and surface property of ZnO thin films as electron transporting layer in perovskite solar cells are crucial for obtaining high-efficient and stable perovskite solar cells. In this work, two different preparation methods of ZnO thin films were carried out and the photovoltaic performances of the subsequent perovskite solar cells were investigated. ZnO thin film prepared by sol–gel method was homogenous but provided high series resistance in solar cells, leading to low short circuit current density. Lower series resistance of solar cell was obtained from homogeneous ZnO thin film from spin-coating of colloidal ZnO nanoparticles (synthesized by hydrolysis–condensation) in a mixture of 1-butanol, chloroform and methanol. The perovskite solar cells using this film achieved the highest power conversion efficiency (PCE) of 4.79% when poly(3-hexylthiophene) was used as a hole transporting layer. In addition, the stability of perovskite solar cells was also examined by measuring the photovoltaic characteristic for six consecutive weeks with the interval of 2 weeks. It was found that using double layers of the sol–gel ZnO and ZnO nanoparticles provided better stability with no degradation of PCE in 10 weeks. Therefore, this work provides a simple method for preparing homogeneous ZnO thin films in order to achieve stable perovskite solar cells, also for controlling their surface properties which help better understand the characteristics of perovskite solar cells.

Nowadays, the power conversion efficiency of organometallic mixed halide perovskite solar cells (PSCs) is beyond 25%. To fabricate highly efficient and stable PSCs, the performance of metal oxide charge transport layers (CTLs) is one of the key factors. The CTLs are employed in PSCs to separate the electrons and holes generated in the perovskite active layer, suppressing the charge recombination rate so that the charge collection efficiency can be increased at their respective electrodes. In general, engineering of metal oxide electron transport layers (ETLs) is found to be dominated in the research community to boost the performance of PSCs due to the resilient features of ETLs such as excellent electronic properties, high resistance to thermal temperature and moisture, ensuring good device stability as well as their high versatility in material preparation. The metal oxide hole transport layers in PSCs are recently intensively studied. The performance of PSCs is found to be very promising by using optimized hole transport materials. This review concisely discusses the evolution of some prevalent metal oxide charge transport materials (CTMs) including TiO2, SnO2, and NiOx, which are able to yield high-performance PSCs. The article begins with introducing the development trend of PSCs using different types of CTLs, pointing out the important criteria for metal oxides being effective CTLs, and then a variety of preparation methods for CTLs as employed by the community for high-performance PSCs are discussed. Finally, the challenges and prospects for future research direction toward scalable metal oxide CTM-based PSCs are delineated.

Crossing Up Charge Extraction Layers

Modification of electron-transport layers with mixed RGO/C60 additive to boost the performance and stability of perovskite solar cells: A comparative study

Perovskite solar cells have gained significant attention due to their high energy conversion efficiency, low cost, and excellent photovoltaic properties. The efficiency and stability of perovskite solar cells can be enhanced by the modification of novel materials which are in the light-absorbing, electron transport, and hole transport layers. Therefore, finding new materials with excellent photovoltaic properties and stable structures is crucial for improving the performances of perovskite solar cells. Black phosphorus, two-dimensional perovskite materials, and quantum dot materials are the research hotspots in recent years, all of which exhibit excellent properties. Using these materials to modify solar cells is an effective way to reinforce the performance of solar cells. This paper introduced these materials briefly. In addition, their applications in the electron transport layer, light-absorbing layer, and hole transport layer of perovskite solar cells were discussed. The impact of utilizing these materials on improving the stability of solar cells were discussed. This work pointed out promising research directions in this field. Exploring novel methods to solve the trap density problem will contribute to further study on this issue. In addition, it is considered that the properties of the hybrid 2D/3D perovskite materials should be explored. Attempting to improve the stability of quantum dot modified solar cells will also be an urgent issue to be addressed in the future.

Judicious choice of transport layer in organic–inorganic halide perovskite solar cells can be one of the essential parameters in photovoltaic design and fabrication techniques. This article reports the effect of optically generated dipoles in transport layer on the photovoltaic actions in active layer in perovskite solar cells with the architecture of indium tin oxide (ITO)/TiO x /CH3NH3PbI3–x Cl x /hole transport layer (HTL)/Au. Here, PTB7‐thieno[3,4‐b]thiophene‐alt‐benzodithiophene and P3HT‐poly(3‐hexylthiophene) are separately used as the HTL with significant and negligible photoinduced dipoles, respectively. Electric field‐induced photoluminescence quenching provides the first‐hand evidence to indicate that the photoinduced dipoles are partially aligned in the amorphous PTB7 layer under the influence of device built‐in field. By monitoring the recombination process through magneto‐photocurrent measurements under device operation condition, it is shown that the photoinduced dipoles in PTB7 layer can decrease the recombination of photogenerated carriers in the active layer in perovskite solar cells. Furthermore, the capacitance measurements suggest that the photoinduced dipoles in PTB7 can decrease charge accumulation at the electrode interface. Therefore, the studies indicate the important role of photoinduced dipoles in the HTL on charge recombination dynamics and provide a fundamental insight on how the polarization in transport layer can influence the device performance in perovskite solar cells.