Thermal Stability Of Perovskite Solar Cells Research Articles

Improved Performance of Air-Processed Perovskite Solar Cells via the Combination of Chlorine Precursors and Potassium Thiocyanate.

Due to their low cost and high efficiency, hybrid perovskite solar cells (PSCs) have shown the most outstanding competitiveness among third-generation photovoltaic (PV) devices. However, several challenges remain unresolved, among which the limited stability is arguably the main. Chlorine (Cl) has been widely employed to yield PV performances, but the Cl-doping mechanism and its role in mixed-halide PSCs are not entirely understood. Here, we investigate the effect of Cl-doping using different precursors such as formamidinium chloride (FACl), cesium chloride (CsCl), and lead chloride (PbCl2), which lead to the incorporation of Cl at different sites of the perovskite crystal. We demonstrate that the stability and efficiency of air-processed PSCs are strongly affected by Cl bonding into the cationic chloride precursor. Furthermore, adding potassium thiocyanate (KSCN) leads to the maximum efficiency of 18.1%, improving the operational stability with only 18% PCE loss after 520 h, stored under ambient conditions. Incorporating CsCl and KSCN presents an effective approach to further boost the performance and thermal stability of PSCs by tailoring the composition of the perovskite's composition. Finally, we used the slot-die method to demonstrate that our strategy is scalable for large-area devices that have shown similar performance. Our results show that fully air-processed and stable PSCs with high efficiency for large production and commercialization are achievable.

A novel perovskite solar cell comprising CsPbI2Br/Cs2SnI6 (CsGeI3) cascade absorbing bilayer and Cr2O3 electron transport material: A theoretical comparison study

In order to prevent the limitation on absorbing energies by a single-layer perovskite solar cells (PSCs), a cell comprising bilayer heterostructure in the form of FTO/Cr2O3/CsPbI2Br +Cs2SnI6 (CsGeI3)/spiro-OMeTAD/Au is simulated and its photovoltaic performance including incident photon-to-current conversion efficiency, fill factor, open circuit voltage and short circuit current is evaluated using SCAPS 1D software package. It is shown by introducing these structures, not only a wider range of the sunlight spectrum is exploited, but also by achieving a favorable band-edge bending as graded band gap, more charge carriers can be collected. Moreover, further improvement in the performance of devices is obtained by optimizing the thickness of absorbing layers and work function of the back electrode. The thermal stability of PSCs is investigated by varying the temperature in the range of 300–480 K and the effect of various electron transport materials (ETMs) on the performance of the cell is evaluated. Under optimized condition, it is found that the efficiencies of the cells with CsPbI2Br+Cs2SnI6 and CsPbI2Br+CsGeI3 bilayer heterostructures increase from 13.38% for non-heterojunction structure to 15.14% and 16.34%, respectively. Furthermore, the simulation results reveal that the photovoltaic cell made of CsPbI2Br+CsGeI3 absorbing layer having higher efficiency and greater thermal stability (compared to PSC made of CsPbI2Br+Cs2SnI6 absorbing layer) is an appropriate and promising candidate as efficient perovskite solar cell.

Hydrophobic 4-(isopropylbenzyl)oxy-substituted metallophthalocyanines as a dopant-free hole selective material for high-performance and moisture-stable perovskite solar cells

Dopant-free hole-transporting materials (HTMs) are necessary to overcome the instability for perovskite solar cells (PSCs) originating from conventional HTMs such as spiro-OMeTAD requiring hygroscopic dopants for future commercialization. Herein, a series of dopant-free HTMs based on peripherally 4-(isopropylbenzyl)oxy-substituted phthalocyanines with different core metals (EG-pZn1, EG-pCu1, and EG-pNi1) are designed and introduced as a hole-transport layer in PSCs for the first time. The introduction of hydrophobic bulky 4-(isopropylbenzyl)oxy moieties to the phthalocyanine structure favors excellent moisture-resistant effect, and good solubility, as well as suppression of charge recombination in PSCs. Three HTMs-based cells afford an impressive efficiency of 17.60% (EG-pNi1), 16.45% (EG-pCu1), and 15.83% (EG-pZn1) with the character of hysteresis-free. More importantly, while EG-pNi1 and EG-pCu1 HTL-based devices can effectively protect perovskite film from moisture which degraded to only 10% of its initial efficiency under humidity level (60–65%) after a period of 20 days, unexpectedly, ∼30% loss of initial efficiency has been observed in EG-pZn1 HTM based devices under the same conditions. Furthermore, EG-pNi1-based devices also show excellent thermal stability, maintaining 95% initial efficiency after aging for 20 days at 85 °C. These results demonstrate the role of peripherally substituted hydrophobic 4-(isopropylbenzyl)oxy group in HTMs on photovoltaic performance and moisture-/thermal-stability of PSCs and its potential in reasonable and effective ways of industrial commercialization of PSCs.

Efficient Perovskite Solar Cells with Enhanced Thermal Stability by Sulfide Treatment

The performance degradation of perovskite solar cells (PSCs) under harsh environment (e.g., heat, moisture, light) is one of the greatest challenges for their commercialization. Herein, a conjugated sulfide 2-mercaptobenzimidazole (2MBI) is applied to significantly improve the photovoltaic properties and thermal stability of PSCs. When treated with heat, 2MBI cross-links with each other on the perovskite surface to facilitate charge transportation, suppress the escape of volatile species, and guide the rearrangement of surface perovskite grains. PSCs with 2MBI modification reach a PCE as high as 21.7% and maintain high-efficiency output during and after thermodestruction at 85 °C, while the unmodified ones suffer severe degradation. Unencapsulated devices after thermodestruction achieve over 98% of initial efficiency after 40-day storage under ambient conditions.

Are Metal Halide Perovskite Solar Cells Ready for Space Applications?

The appeal of metal halide perovskite solar cells (PSCs) has been widely demonstrated in the field of photovoltaic technology. On account of the excellent optical and electrical properties, as well as compatibility with flexible substrates, the PSCs also hold the highest record of specific power for lightweight solar cell devices, suggesting excellent promise in space applications. Hence, there is increasing interest in the performance of PSCs in space environments where radiation beams and thermal cycling can cause extreme stress on the devices. In this Perspective, we provide a brief summary of the research on PSCs for space applications. The radiation tolerance and thermal stability of PSCs and the fundamental mechanisms are discussed and analyzed. Key challenges facing PSC technology toward future space applications are demonstrated. This Perspective features the prospect of PSCs as the next frontier in space PV technology.

Cesium-doped Ti3C2Tx MXene for efficient and thermally stable perovskite solar cells

Ti3C2Tx MXenes have been shown to be promising candidates for use in various applications. Herein, we prepare functionalized Ti3C2Tx MXene nanosheets doped with cesium (Cs) and introduce them into a lead iodide (PbI2) precursor solution for perovskite solar cells (PSCs) through a two-step deposition method, combining the advantages of both additives. Our theoretical and experimental analysis reveal that cesium plays an important role in improving perovskite crystallization and thus leads to enlarged crystal grains, long-lived carrier lifetimes, and reduced charge recombination compared with the devices fabricated without and with undoped Ti3C2Tx MXene. PSCs integrated with cesium-doped Ti3C2Tx MXene deliver high photovoltaic efficiency of up to 21.57% with excellent thermal stability. The incorporation of Cs-Ti3C2Tx paves the way to further improve the photovoltaic performance and thermal stability of PSCs by indirectly introducing dopants.

Cesium-Doped Ti <sub>3</sub>C <sub>2</sub>T <sub>x</sub> MXene for Efficient and Thermally Stable Perovskite Solar Cells

Ti3C2Tx MXenes have been shown to be a promising candidate for use in various applications. Herein, we prepared functionalized Ti3C2Tx MXene nanosheets doped with cesium (Cs) and introduced them into lead iodide (PbI2) precursor solution for perovskite solar cells (PSCs) through a two-step deposition method. Our theoretical and experimental analysis revealed that Cs plays an important role in improving the perovskite crystallization and thus leading to enlarged crystal grains, long-lived carrier lifetimes, and reduced charge recombination as compared to the devices fabricated without and with undoped Ti3C2Tx MXene. PSCs integrated with Cs doped Ti3C2Tx MXene delivered a high photovoltaic efficiency of up to 21.57% with excellent thermal stability. The incorporation of Cs-Ti3C2Tx paves the way to further improve the photovoltaic performance and thermal stability of PSCs.

The Relation of Phase-Transition Effects and Thermal Stability of Planar Perovskite Solar Cells.

A power conversion efficiency of over 20% has been achieved in CH3NH3PbI3‐based perovskite solar cells (PSC), however, low thermal stability associated with the presence of a phase transition between tetragonal and cubic structures near room temperature is a major issue that must be overcome for future practical applications. Here, the influence of the phase transition on the thermal stability of PSCs is investigated in detail by comparing four kinds of perovskite films with different compositions of halogen atoms and organic components. Thermally stimulated current measurements reveal that a large number of carrier traps are generated in solar cells with the perovskite CH3NH3PbI3 as a light absorber after operation at 85 °C, which is higher than the phase‐transition temperature. Electrochemical impedance spectroscopy measurements further exclude effects of a possible morphology change on the formation of carrier traps. These carrier traps are detrimental to the thermal stability. The thermogravimetric analysis does not show a decomposition for any of the materials in the temperature range relevant for operation. The perovskite alloys do not have this phase transition, resulting in effectively suppressed formation of carrier traps. PSCs with improved thermal stability under the standard thermal cycling test are demonstrated.