2D metal halide perovskites have enabled significant stability improvements in perovskite devices, particularly in resistance to moisture. However, some 2D perovskites are even more susceptible to photooxidation compared to 3D perovskites. This is particularly true for more commonly investigated RuddlesdenPopper (RP) perovskites, which exhibit increased susceptibility to photoinduced degradation compared to Dion-Jacobson (DJ) perovskites. Comparisons between different RP and DJ perovskites reveal that this phenomenon cannot be explained by commonly proposed differences in superoxide ion generation, interlayer distance, or lattice structural rigidity differences. Instead, the resistance to photooxidation of DJ perovskites can be attributed to a decreased likelihood of double deprotonation events (compared to single deprotonation events in RP perovskites) required for the loss of organic cations and perovskite decomposition. Consequently, DJ perovskites are less susceptible to oxidative degradation (induced both photo- and electrochemically), which leads to improved operational stability of solar cells based on these materials.

Herein, the effect of multicomponent composite encapsulation on the stability of perovskite thin films and perovskite solar cells, as well as lead leakage upon water immersion, is investigated. The encapsulation is simple and low cost since it is entirely deposited by solution processed techniques in the ambient atmosphere. It consists of a spray‐coated composite layer sandwiched between two spin‐coated layers. The composite layer contains hygroscopic nanomaterials, oxygen scavengers, and lead adsorbing nanomaterials, which enables reduced lead leakage and improved stability of encapsulated perovskite during storage in ambient, immersion in water, as well as illumination in dry air. The encapsulation layers show high transmittance and did not have a significant effect on the short‐circuit current density and open‐circuit voltage despite the deposition of encapsulation in ambient air. The encapsulated devices retain 80% of their initial performance after 4 h of immersion in water.

Flexible perovskite solar cells (fPSCs) prepared on flexible plastic substrates exhibit poor stability under illumination in ambient, due to inferior gas barrier properties of plastic substrates. Herein, we investigated effect of different modifications of the back surface of the substrate to improve stability under illumination in ambient. T 80 under simulated solar illumination at maximum power point in ambient (ISOS‐L‐1) can be increased from 80 h to over 350 h with the deposition of a single layer (by spin‐coating or by atomic layer deposition (ALD)). While ALD layers resulted in the best T 80 value and significant reduction of the oxygen transmission rate compared to other modifications even for very low film thickness (≈10 nm), a simple solution‐processed spin‐on‐glass barrier layer also enables significant (more than 4 times) improvement in device stability. This work illustrates the importance of barrier layers for decreasing the ingress of oxygen and moisture into fPSCs through the plastic substrate.

Perovskite solar cells (PSCs) have gained significant attention as a promising photovoltaic technology due to their excellent power conversion efficiency (PCE) and cost-effective fabrication methods. However, ensuring long-term stability and addressing environmental concerns are vital challenges for successful commercialization. In this study, we explore metal oxide-based thin film encapsulation methods to enhance the performance and durability of PSCs. We considered back surface modification for flexible PSCs, as well as top surface encapsulation applicable to both rigid and flexible devices. Our results reveal increased operational stability and device performance, effectively addressing critical challenges in PSC commercialization.

As an emerging candidate material for photovoltaic applications, metal halide perovskites are well-known for their high power conversion efficiency and fabrication convenience. Mixed-halide perovskites, specifically those with bromide (Br) and iodide (I) anions, are a popular choice for the light-absorbing layer due to their wide bandgap, a critical consideration as perovskite-based tandem solar cells make a major effort towards commercialization. However, the photo-induced halide phase segregation in mixed halide perovskites under illumination can severely damage the device lifetime, so it is of great importance to realize appropriate strategies to slow down or inhibit this photo-segregation phenomenon. In this work, we applied both doping (using Cu and Li-Cu dopants) and surface modification (using two different phosphonic acid-based self-assembled monolayers) strategies to the nickel oxide (NiOx) hole transporting layer (HTL) under perovskite films in solar cell devices to adjust its hole collection capability and carefully examine the photo-segregation process via in situ UV-visible absorption spectrum monitoring. This enables us to elucidate the relationship between the properties of HTL and the photo-segregation process and work towards an optimal HTL. Hole trapping, leading to iodide oxidation and extraction, is a major pathway leading to halide ion mobility. We expect the existence of a HTL can prevent accumulation of holes in the bulk perovskite film and thus slow down the process of photo-segregation. Obtained results for both 2D and 3D mixed halide perovskite films are discussed in detail.

Many recent advances in metal halide perovskite solar cell (PSC) performance are attributed to surface treatments which passivate interfacial trap states, minimise charge recombination and boost photovoltages. Surprisingly, these photovoltages exceed the cells' built-in potentials, often with large energetic offsets reported between the perovskite and transport layer semiconductor band edges - contradicting standard photovoltaic design principles. Here we show that this tolerance to energetic offsets results from mixed ionic/electronic conduction in the perovskite layer. Combining drift-diffusion simulations with experiments probing the current-voltage performance of PSCs as a function of ion distribution, we demonstrate that electrostatic redistribution of ionic charge reduces surface recombination currents at steady-state, increasing the photovoltage by tens to hundreds of millivolts. Thus, mobile ions can reduce the sensitivity of photovoltage to energetic misalignments at perovskite/transport layer interfaces, benefitting overall efficiency. Building on these insights, we show how photovoltaic design principles are modified to account for mobile ions.

Various phosphonic acid based self-assembled monolayers (SAMs) have been commonly used for interface modifications in inverted perovskite solar cells. This typically results in significant enhancement of the hole extraction and consequent increase in the power conversion efficiency. However, the surface coverage and packing density of SAM molecules can vary, depending on the chosen SAM material and underlying oxide layer. In addition, different SAM molecules have diverse effects on the interfacial energy level alignment and perovskite film growth, resulting in complex relationships between surface modification, efficiency, and lifetime. Here we show that ethanolamine surface modification combined with [2-(9H-carbazol-9-yl)ethyl]phosphonic acid (2PACz) results in significant improvement in device stability compared to devices with 2PACz modification only. The significantly smaller size of ethanolamine enables it to fill any gaps in 2PACz coverage and provide improved interfacial defect passivation, while its different chemical structure enables it to provide complementary effects to 2PACz passivation. Consequently, the perovskite films are more stable under illumination (slower photoinduced segregation), and the devices exhibit significant stability enhancement. Despite similar power conversion efficiencies (PCE) between 2PACz only and combined ethanolamine-2PACz modification (PCE of champion devices ∼21.6-22.0% for rigid and ∼20.2-21.0% for flexible devices), the T80 lifetime under simulated solar illumination in ambient is improved more than 15 times for both rigid and flexible devices.

Iron-based materials are among the most commonly used oxygen scavengers. Here, we investigated the mesoporous silica nanosphere (MSN)-supported iron-based scavengers, such as FeOx nanoparticles and different atomic layer deposition (ALD) coatings (FeOx and Fe). We found that the scavenger performance is a result of a complex interplay between available Brunauer-Emmett-Teller surface area and the scavenger composition, with the combination of infiltrated nanoparticles and Fe-ALD coating resulting in the best performance. When the glucose-based treatment of MSN is used to further enhance oxygen scavenging capacity, Fe-ALD coating yields the best performance, with a high oxygen adsorption capacity of 126.8 mL/g. ALD deposition of Fe represents a versatile method to introduce Fe-based oxygen scavengers onto different supports, and it can facilitate the integration of scavengers with different types of packaging, as the deposition can be performed at a low temperature of 150 °C.

To avoid foodborne illness, maintaining the prolonged food freshness and real-time food quality/health monitoring are the challenges to be addressed in this era. Development of active food packaging is an advancing research for real-time food health monitoring. In this study, mesoporous silica nanospheres (MSNs) have been synthesized with controlled size (>100nm) and porosity by using modified Stöber method. These MSNs are capable of adsorbing oxygen by physisorption thus can be used as oxygen scavengers for food packaging materials to extend shelf life of the food products. Furthermore, this study aims to incorporate active metal oxide nanoparticles (MNPs) in the pores of synthesized MSNs to extend its applications as oxygen scavenging and detection to avoid oxygen produced food degradation. The MNPs with an average size of <10 nm were successfully synthesized with stable dispersions. The active MNPs including SnO2, Fe2O3, ZnO and TiO2 (<10 nm) have been incorporated in the pores of MSNs. The MNPs were incorporated in the MSNs using i) Synthesis of MNPs followed by in-situ synthesis of MSNs, ii) synthesis of MSNs first followed by in-situ synthesis of MNPs in the pores of MSNs and, (iii) Synthesis of MSNs and MNPs separately and mixing of stable suspension of both MSNs and MNPs to achieve the best results for oxygen scavenging. The results indicated that first route was more successful for embedding the MNPs in the pores of MSNs. The oxygen scavenging efficiency of the MNPs incorporated MSNs were evaluated.