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In perovskite solar cells (PSCs), a common characteristic of highly effective interface passivation materials is low conductivity. Gains in voltage are thus often disproportionately offset by resistive losses. Local contact approaches can minimize this trade‐off and have a proven track record in conventional silicon photovoltaics. Indeed, recent record efficiencies for centimeter‐scale PSCs exploit architectures where the passivation layer partially covers the perovskite‐transport layer interface. Herein, a three‐dimensional numerical device model is used to determine practical performance limits to local contact geometries and consider both the optimum contact dimensions and the trade‐offs involved in relaxing these dimensions for ease of fabrication. It is observed that the potential for substantial power conversion efficiency (PCE) increases with local contacts. In devices where power loss occurs solely through recombination at the contacted interface, PCE can be enhanced by up to 10% absolute compared to a full‐area contact. However, optimum PCEs depend on contacts on the order of nanometers. It is shown that more fabrication‐friendly micrometer‐scale contacts still boost PCE, but the absolute enhancement falls short due to the relatively low bulk perovskite charge carrier diffusion length. This may ultimately motivate methods of interface engineering that produce "effective" local contact geometries at nanometer scales, such as via self‐forming layers. [ABSTRACT FROM AUTHOR]

Perovskite solar cell (PSC) technology is a promising candidate for space applications because of its high power‐to‐weight ratio, low‐cost fabrication process, and good tolerance to high‐energy particle radiation. In this work, perovskite films and resultant high‐efficiency PSCs are assessed under 10 MeV proton radiation at fluences in the range 1e12–1e14 p cm−2, which are equivalent to 1 to 100 years in geostationary orbit (GEO) without any shielding or cover. For the first time, void formation and material ablation are detected on perovskite films, indicating structural damage of the materials under the proton radiation. Furthermore, ions inside the devices especially Au and Pb ions are displaced to underlying layers under the proton bombardment. These lead to the degradation of PSCs to ≈89% of the initial performance (from 24.1% to 21.4%) at the highest dose. The experimental results are supported by previous simulation works with a good fit in all optoelectronic parameters. This study provides insights into the degradation mechanism of PSCs under proton radiation and paves the way for the utilization of PSCs in space applications. [ABSTRACT FROM AUTHOR]

Due to the limited interface contact and weak interfacial interaction, planar heterojunction perovskite solar cells (PSCs) have space for further improvement. Herein, a structural and chemical crosslinking interface is proposed and constructed by introducing an extra layer, which blends tin dioxide (SnO2) nanoparticles with chloride salts. Since the incorporated materials can be dissolved during the fabrication of perovskite, the quality of perovskite films is improved, leading to larger grain size and reduced trap‐state density. Also, more chloride ions at the SnO2/perovskite interface are observed and the interaction between Cl− and Sn4+ is confirmed. It results in more pronounced n‐type SnO2 with better conductivity and deeper conduction bands, leading to preferable energy level alignment between SnO2 and perovskite. Consequently, the open‐circuit voltage and fill factor of the devices increase, and target cells present better stability, retaining 98% of initial efficiencies after >10 000 h storage in dry air (≈5% relative humidity) and maintaining 85.50% of the initial efficiency after 1000 h of operation under light. This strategy enables the achievement of 25.28% efficiency with a low bandgap (1.53 eV) perovskite composition, and it is confirmed to be universal when other related materials are utilized. [ABSTRACT FROM AUTHOR]

Perovskite solar cell technology offers a promising power option for space applications due to its potential properties of high power‐to‐weight ratios and space‐radiation tolerance. Herein, a new simulation‐based method is introduced to predict the degradation of perovskite solar cells under proton radiation. The approach uses ion scattering simulations to generate depth‐dependent defect profiles as a function of proton energy and fluence, which are then incorporated into optoelectronic simulations to predict the degradation. The method to study the impact of perovskite compositions on radiation tolerance is applied and an inorganic perovskite CsPbI2Br and an organic–inorganic perovskite FAMAPbI3 is compared. The simulations predict that CsPbI2Br and FAMAPbI3 cells retain 62% and 65% of their initial efficiencies after a 100 keV fluence of 1e14 cm−2, respectively. For comparison, unshielded III–V solar cells display similar degradation for proton fluences 3–4 orders of magnitude lower. It is also shown that the radiation direction must be considered when interpreting and predicting radiation tolerance, as the spatial overlap between photogenerated carriers and radiation‐induced defects has a significant impact on cell performance. Finally, a method to predict mission end‐of‐life performance of perovskite cells is demonstrated, taking into account the full proton radiation energy spectrum and fluence and the incident direction. [ABSTRACT FROM AUTHOR]

Understanding carrier recombination mechanisms and quantifying recombination dynamics are key to improving the performance of state-of-the-art perovskite solar cells. Here, we present a method to quantify the quality of perovskite thin films using a combination of steady-state and transient photoluminescence measurements. The combined experimental datasets are fitted using a single, general recombination model, from which detailed trap and recombination parameters can be extracted, and the accuracy of the fitted values is estimated. This approach expands the application of photoluminescence measurements to include quantitative evaluation of the most relevant defect characteristics, including trap density, energy level, and carrier capture coefficients. We apply this approach to compare perovskite films of the widely studied methyl-ammonium lead iodide (MAPbI3) with the high performance quadruple-cation, mixed-halide composition Cs0.07Rb0.03(FA0.85MA0.15)0.9Pb(I0.85Br0.15)3. Our quantitative analysis of trap properties in these perovskite films suggests that the superior performance of the quadruple cation films may be due to a greatly reduced electron capture coefficient, rather than a significant reduction in the trap density. [ABSTRACT FROM AUTHOR]

One of the important factors in the performance of perovskite solar cells (PSCs) is effective defect passivation. Dimensional engineering technique is a promising method to efficiently passivate non‐radiative recombination pathways in the bulk and surface of PSCs. Herein, a passivation approach for the perovskite/hole transport layer interface is presented, using a mixture of guanidinium and n‐octylammonium cations introduced via GuaBr and n‐OABr. The dual‐cation passivation layer can provide an open‐circuit voltage of 1.21 V with a power conversion efficiency of 23.13%, which is superior to their single cation counterparts. The mixed‐cation passivation layer forms a 1D/2D perovskite film on top of 3D perovskite, leading to a more hydrophobic and smoother surface than the uncoated film. A smooth surface can diminish non‐radiative recombination and enhance charge extraction at the interface making a better contact with the transport layer, resulting in improved short‐circuit current. In addition, space charge‐limited current measurements show a three times reduction in the trap‐filled limit voltage in the mixed‐cation passivated sample compared with unpassivated cells, indicating fewer trapped states. The shelf‐life stability test in ambient atmosphere with 60% relative humidity as well as light‐soaking stability reveal the highest stability for the dual‐cation surface passivation. [ABSTRACT FROM AUTHOR]

Hybrid organic–inorganic perovskite solar cells (PSCs) are one of the most promising candidates for next generation photovoltaics. Further improvement in their performance, particularly efficiency, durability and reproducibility, requires a deep understanding of recombination losses during fabrication and within a device itself. In this work, we report a contactless, imaging‐based procedure to spatially resolve electronic properties of PSCs including implied open‐circuit voltage (iVoc) and its temperature coefficient, ideality factor (nid) and activation energy of recombination (EA) by employing illumination intensity and temperature‐dependent photoluminescence. The illumination intensity dependence of iVoc allows the extraction of nid whereas its temperature dependence allows the extraction of the temperature coefficient and EA. This imaging approach is then applied to investigate changes of these electronic parameters on fully and partially fabricated devices. [ABSTRACT FROM AUTHOR]

The tandem cell structure is the most promising solution for the next generation photovoltaic technology to overcome the single‐junction Shockley–Queisser limit. The fabrication of a perovskite/c‐Si monolithic tandem device has not yet been demonstrated on a c‐Si bottom cell produced from an industrial production line. Here, a c‐Si cell with a tunneling oxide passivating contact (TOPCon) structure produced on a production line as the bottom cell of a tandem device, and a top cell featuring solution‐processed perovskite films to form the tandem device are used. The c‐Si cell features a rough damage etched, but untextured front surface from the wafering processes. To combat the challenge of rough surfaces, several strategies to avoid shunt paths across carrier transport layers, absorber layers, and their interfaces are implemented. Moreover, the origin of reflection loss on this planar structure is investigated and the reflection loss is managed to below 4 mA cm−2. In addition, the source of the voltage loss from the TOPCon bottom cell is identified and the device structure is redesigned to be suitable for tandem applications while still using mass production feasible fabrication methods. Overall, 27.6% efficiency is achieved for a monolithic perovskite/c‐Si tandem device, with significant potential for future improvements. [ABSTRACT FROM AUTHOR]

A key limitation in perovskite solar cell (PSC) performance is suboptimal electronic properties at the perovskite–transport layer (TL) interfaces, which result in parasitic nonradiative recombination. Interface recombination depends on the concentration of recombination‐active defects, but as a recombination event requires both an electron and a hole, the magnitude and sign of charge accumulation at the perovskite–TL heterojunctions are also critical. Here, we employ a well‐established numerical ion‐electron drift‐diffusion model of PSCs to illustrate how the work function of the transport layer is an important factor in determining the total recombination activity at the perovskite interfaces. We show that the equilibrium electrostatics of the perovskite–TL heterojunctions, which are determined by the work function difference between the two materials, can result in increased recombination rates for any given concentration of interface defects. As a case study, we compare PSCs incorporating a NiOX hole transport layer with those with a spiro‐OMeTAD. We show that the work function of NiOX can induce greater electron accumulation at the perovskite–NiOX interface, which leads to increased interface recombination. Finally, a higher ion concentration is found to be beneficial to overall device performance by displacing accumulated electrons or holes at the TL interfaces and thus reducing recombination rates. [ABSTRACT FROM AUTHOR]

Perovskite solar cells are a potential game changer for the photovoltaics industry, courtesy of their facile fabrication and high efficiency. Despite this, commercialization is being held back by poor stability. To become economically feasible for commercial production, perovskite solar cells must meet or exceed industry standards for operational lifetime and reliability. In this regard, mixed dimensional 2D‐3D perovskite solar cells, incorporating long carbon‐chain organic spacer cations, have shown promising results, with enhancement in both device efficiency and stability. Dimensional engineering of perovskite films requires a delicate balance of 2D and 3D perovskite composition to take advantage of the specific properties of each material phase. This review summarizes and assesses the current understanding, and apparent contradictions in the state‐of‐the‐art mixed dimensional perovskite solar cell literature regarding the origin of stability and performance enhancement. By combining and comparing results from experimental and theoretical studies it is focused on how the perovskite composition, film formation methods, additive and solvent engineering influence efficiency and stability, and identify future research directions to further improve both key performance metrics. [ABSTRACT FROM AUTHOR]

Dimensional engineering of perovskite films is a promising pathway to improve the efficiency and stability of perovskite solar cells (PSCs). In this context, surface or bulk passivation of defects in 3D perovskite film by careful introduction of 2D perovskite plays a key role. Here the authors demonstrate a 2D perovskite passivation scheme based on octylammonium chloride, and show that it provides both bulk and surface passivation of 1.6 eV bandgap 3D perovskite film for highly efficient (≈23.62%) PSCs with open‐circuit voltages up to 1.24 V. Surface and depth‐resolved microscopy and spectroscopy analysis reveal that the Cl− anion diffuses into the perovskite bulk, passivating defects, while the octylammonium ligands provide effective, localized surface passivation. The authors find that the Cl− diffusion into the perovskite lattice is independent of the 2D perovskite crystallization process and occurs rapidly during deposition of the 2D precursor solution. The annealing‐induced evaporation of Cl from bulk perovskite is also inhibited in 2D–3D perovskite film as compared to pristine 3D perovskite, ensuring effective bulk passivation in the relevant film. [ABSTRACT FROM AUTHOR]

Early prediction of spatially resolved performance of perovskite solar cells (PSCs) is essential for process monitoring, control and fault diagnosis, and upscaling of this emerging technology. Herein, a fast, nonde structive, contactless imaging‐based approach is developed to visualize the spatial distribution of possible light current density−voltage (pseudo‐J−V) curves on finished and partly finished cells. This allows for the extraction of other critical spatially resolved properties including implied open‐circuit voltage and pseudo‐fill factor. The technique is applied to systematically investigate various degradation behaviors on PSCs including thermal stability, light soaking, and ambient air exposure. Finally, it is used to predict pseudo‐J−V curves of various perovskite films with different compositions. These results demonstrate the significant value of this fast imaging technique for the research and development of PSCs ranging from material selection, process optimization, to degradation study. [ABSTRACT FROM AUTHOR]

Crystalline, dense, and uniform perovskite thin films are crucial for achieving high‐power conversion efficiency solar cells. Herein, a universal method of fabricating highly crystalline and large‐grain perovskite films via crystal engineering is demonstrated. Anion exchange of Cl− and I−, and annealing perovskite films, in an ultraconfined and uniform temperature enclosed space with saturated MAI (or FAI) vapor using hot‐pressing sublimation technology are conducted. This process ensures a rapid crystal growth rate due to fast exchange between the gas phase and the crystalline film to reduce vertically oriented grain boundaries. The generation of the commonly observed PbI2 phase is also suppressed due to the chemical equilibrium state during the thermal annealing process. Using this approach, pinhole‐free perovskite films with preferred crystal orientation and micrometer‐scale grains are obtained, leading to a high steady‐state efficiency of 22.15% based on mixed‐cation perovskite composition. In addition, devices based on different perovskite compositions all exhibit enhanced photovoltaic performance based on the crystal engineering method. The device (without encapsulation) has an efficiency loss of about only 4% after 2520 h of aging in ambient conditions and retains 87% of its initial efficiency after 1000 h of continuous 1 Sun light soaking, thus demonstrating considerably improved stability. [ABSTRACT FROM AUTHOR]

The article commences with a review focusing on three critical aspects of the perovskite/Si tandem technology: the evolution of efficiencies to date, comparisons of Si subcell choices, and the interconnection design strategies. Building on this review, a clear route is provided for minimizing optical losses aided by optical simulations of a recently reported high‐efficiency perovskite/Si tandem system, optimizations which result in tandem current densities of ≈20 mAcm−2 with front‐side texture. The primary focus is on electrical modeling on the Si‐subcell, in order to understand the efficiency potential of this cell under filtered light in a tandem configuration. The possibility of increasing the Si subcell efficiency by 1% absolute is offered through joint improvements to the bulk lifetime, which exceeds 4 ms, and improves surface passivation quality to saturation current densities below 10 fA cm−2. Polycrystalline‐Si/SiOx passivating contacts are proposed as a promising alternative to partial‐area rear contacts, with the potential for further simplifying cell fabrication and improving device performance. A combination of optical modeling of the complete tandem structure alongside electrical modeling of the Si‐subcell, both with state‐of‐the‐art modeling tools, provides the first complete picture of the practical efficiency potential of perovskite/Si tandems. [ABSTRACT FROM AUTHOR]

Instability in perovskite solar cells is the main challenge for the commercialization of this solar technology. Here, a contactless, nondestructive approach is reported to study degradation across perovskite and perovskite/silicon tandem solar cells. The technique employs spectrally and spatially resolved absorptivity at sub‐bandgap wavelengths of perovskite materials, extracted from their luminescence spectra. Parasitic absorption in other layers, carrier diffusion, and photon smearing phenomena are all demonstrated to have negligible effects on the extracted absorptivity. The absorptivity is demonstrated to reflect real degradation in the perovskite film and is much more robust and sensitive than its luminescence spectral peak position, representing its optical bandgap, and intensity. The technique is applied to study various common factors which induce and accelerate degradation in perovskite solar cells including air and heat exposure and light soaking. Finally, the technique is employed to extract the individual absorptivity component from the perovskite layer in a monolithic perovskite/silicon tandem structure. The results demonstrate the value of this approach for monitoring degradation mechanisms in perovskite and perovskite/silicon tandem cells at early stages of degradation and various fabrication stages.Spectrally and spatially resolved absorptivity at sub‐bandgap wavelengths of perovskite materials, extracted from their luminescence spectra, is employed to study degradation across perovskite and perovskite/silicon tandem solar cells. The absorptivity is demonstrated to reflect real degradation in the perovskite film and is much more robust and sensitive than its luminescence spectral peak position, representing its optical bandgap and intensity. [ABSTRACT FROM AUTHOR]

The open-circuit voltage ( VOC) and fill factor are key performance parameters of solar cells, and understanding the underlying mechanisms that limit these parameters in real devices is critical to their optimization. Device modeling is combined with luminescence and cell current-voltage ( I- V) measurements to show that carrier transport limitations within the cell can significantly reduce the cell voltage around the maximum power point as well as, under certain conditions, at VOC. An important consequence is that the cell terminal voltage cannot be assumed a priori to be only limited by parasitic recombination. It is demonstrated that luminescence-based measurements can be used to reconstruct cell I- V curves with removal of any transport limitation effects, which allows the contribution of recombination, shunt resistance, and series resistance on the fill factor to be clarified. Such luminescence-based measurements allow the contactless characterization of cells and cell precursor structures, and should prove highly valuable as a diagnostic tool for the development of new cell structures and large-area cells. [ABSTRACT FROM AUTHOR]

Rubidium (Rb) is explored as an alternative cation to use in a novel multication method with the formamidinium/methylammonium/cesium (Cs) system to obtain 1.73 eV bangap perovskite cells with negligible hysteresis and steady state efficiency as high as 17.4%. The study shows the beneficial effect of Rb in improving the crystallinity and suppressing defect migration in the perovskite material. The light stability of the cells examined under continuous illumination of 12 h is improved upon the addition of Cs and Rb. After several cycles of 12 h light-dark, the cell retains 90% of its initial efficiency. In parallel, sputtered transparent conducting oxide thin films are developed to be used as both rear and front transparent contacts on quartz substrate with less than 5% parasitic absorption of near infrared wavelengths. Using these developments, semi-transparent perovskite cells are fabricated with steady state efficiency of up to 16.0% and excellent average transparency of ≈84% between 720 and 1100 nm. In a tandem configuration using a 23.9% silicon cell, 26.4% efficiency (10.4% from the silicon cell) in a mechanically stacked tandem configuration is demonstrated which is very close to the current record for a single junction silicon cell of 26.6%. [ABSTRACT FROM AUTHOR]

In addition to a good perovskite light absorbing layer, the hole and electron transport layers play a crucial role in achieving high-efficiency perovskite solar cells. Here, a simple, one-step, solution-based method is introduced for fabricating high quality indium-doped titanium oxide electron transport layers. It is shown that indium-doping improves both the conductivity of the transport layer and the band alignment at the ETL/perovskite interface compared to pure TiO2, boosting the fill-factor and voltage of perovskite cells. Using the optimized transport layers, a high steady-state efficiency of 17.9% for CH3NH3PbI3-based cells and 19.3% for Cs0.05(MA0.17FA0.83)0.95Pb(I0.83Br0.17)3-based cells is demonstrated, corresponding to absolute efficiency gains of 4.4% and 1.2% respectively compared to TiO2-based control cells. In addition, a steady-state efficiency of 16.6% for a semi-transparent cell is reported and it is used to achieve a four-terminal perovskite-silicon tandem cell with a steady-state efficiency of 24.5%. [ABSTRACT FROM AUTHOR]

Tandem Solar Cells: Spatially and Spectrally Resolved Absorptivity: New Approach for Degradation Studies in Perovskite and Perovskite/Silicon Tandem Solar Cells (Adv. In article number 1902901, Hieu T. Nguyen and co-workers employ spectrally and spatially resolved absorptivity at sub-bandgap wavelengths of perovskite materials, extracted from their luminescence spectra, to study degradation across perovskite and perovskite/silicon tandem solar cells. Absorptivity, degradation, perovskite, photoluminescence, tandem. [Extracted from the article]

In article number 1802790, Daniel Macdonald, Hieu T. Nguyen, and co‐workers develop a fast, non‐destructive, camera‐based method to capture optical bandgap images of perovskite solar cells with micron‐scale spatial resolution. This technique allows them to probe relative variations in optical bandgaps across various solar cells, and to resolve optical bandgap inhomogeneity within the same device due to material degradation and impurities. The results are independently confirmed with other optical‐based techniques. [ABSTRACT FROM AUTHOR]

A fast, nondestructive, camera‐based method to capture optical bandgap images of perovskite solar cells (PSCs) with micrometer‐scale spatial resolution is developed. This imaging technique utilizes well‐defined and relatively symmetrical band‐to‐band luminescence spectra emitted from perovskite materials, whose spectral peak locations coincide with absorption thresholds and thus represent their optical bandgaps. The technique is employed to capture relative variations in optical bandgaps across various PSCs, and to resolve optical bandgap inhomogeneity within the same device due to material degradation and impurities. Degradation and impurities are found to both cause optical bandgap shifts inside the materials. The results are confirmed with micro‐photoluminescence spectroscopy scans. The excellent agreement between the two techniques opens opportunities for this imaging concept to become a quantified, high spatial resolution, large‐area characterization tool of PSCs. This development continues to strengthen the high value of luminescence imaging for the research and development of this photovoltaic technology. A fast, nondestructive, camera‐based method to capture optical bandgap images of perovskite solar cells with micrometer‐scale spatial resolution is developed. This technique allows for the probing of relative variations in optical bandgaps across various solar cells, and for the resolution of bandgap inhomogeneity within the same device due to material degradation and impurities. The results are independently confirmed with other optical‐based techniques. [ABSTRACT FROM AUTHOR]

Charge accumulation at the electron and hole transport layers generates anomalous electrical behavior in perovskite solar cells (PSCs). Hysteresis in the current–voltage characteristic and recombination at the interfaces are the clearest manifestations of this phenomenon, which compromises device performance and stability. Here, the underlying charge‐carrier dynamics of a variety of PSCs are investigated by analyzing their transient photocurrent response. Towards shorter time scales, PSCs often show increasingly severe hysteretic responses. This phenomenon is correlated with the presence of interfacial accumulated charges that hinders the photogenerated carrier extraction process. However, introducing passivating contacts improves the carrier‐injection properties and the devices become completely hysteresis free. These results underline the importance of contact passivation for PSCs and the need to further develop new passivating interlayers that simultaneously eliminate charge‐carrier recombination and provide selective transport for each carrier type at the PSC's contacts. Perovskite ions, under the influence of an electric field, migrate and accumulate at transport layer interfaces. This reduces the extraction of photo‐generated carriers and induces hysteresis in the current/voltage scan. Here, a solution via contact‐passivation of the electron extraction layer is presented. The passivating contacts reduce the influence of the ions and greatly improve the overall performances of solar cells. [ABSTRACT FROM AUTHOR]

The performance of state‐of‐the‐art perovskite solar cells is currently limited by defect‐induced recombination at interfaces between the perovskite and the electron and hole transport layers. These defects, most likely undercoordinated Pb and halide ions, must either be removed or passivated if cell efficiencies are to approach their theoretical limit. In this work, a universal double‐side polymer passivation approach is introduced using ultrathin poly(methyl methacrylate) (PMMA) films. Very high‐efficiency (≈20.8%) perovskite cells with some of the highest open circuit voltages (1.22 V) reported for the same 1.6 eV bandgap are demonstrated. Photoluminescence imaging and transient spectroscopic measurements confirm a significant reduction in nonradiative recombination in the passivated cells, consistent with the voltage increase. Analysis of the molecular interactions between perovskite and PMMA reveals that the carbonyl (CO) groups on the PMMA are responsible for the excellent passivation via Lewis‐base electronic passivation of Pb2+ ions. This work provides new insights and a compelling explanation of how PMMA passivation works, and suggests future directions for developing improved passivation layers. Interface recombination is a dominant loss mechanism in perovskite solar cells. Double‐side passivation of perovskite solar cells using ultrathin films of poly(methyl methacrylate) (PMMA) can boost open circuit voltages up to 1.22 V. This results from the carbonyl (CO) group of the Lewis‐base polymer PMMA, which effectively passivates under‐coordinated Pb atoms (Pb2+) at the perovskite/transport layer interfaces. [ABSTRACT FROM AUTHOR]

Abstract The stability of perovskite solar cells (PSCs) is one of the major challenges to their commercialization. In this work, the stability of state-of-the-art mesoporous PSCs employing multi-cation mixed-halide perovskite and poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA) as the hole-transport-layer (HTL) is studied under illumination at an elevated temperature in N 2 environment. The Rb in the quadruple-cation perovskite is found to segregate when the film undergoes aging under simultaneous light and heat exposure. More importantly, the PTAA layer prevents diffusion of gold into the perovskite layer when aged at 85 °C in the dark, but not under light. As a result, the PSCs thermally aged under light degrade much more severely than cells thermally aged in the dark. Therefore, the term Light and elevated Temperature Induced Degradation (LeTID) is introduced for PSCs. The effect is also evident for PCSs employing a copper(II) 2,9,16,23-tetra-tert-butyl-29H,31H-phthalocyanine (CuPC) HTL. This effect seriously impacts the operational stability of PSCs and it might not be detected with the current stress tests defined in the IEC-61646 standard. PSCs with a transparent contact and robust perovskite composition are developed with improved stability against LeTID. The cells retain more than 90% of the initial efficiency after > 160 h operating under illumination at 85 °C in N 2 environment. Graphical abstract fx1 Highlights • Perovskite solar cells degrade when operating under light at elevated temperatures, which can be referred as LeTID effect. • The LeTID effect is mainly caused by the diffusion of the metal contact into the perovskite active layer. • The Rb in the quadruple-cation perovskite segregates into Rb-rich phases when the films are aged under light and heat. • Perovskite solar cells with semi-transparent contacts are stable against the LeTID effect. [ABSTRACT FROM AUTHOR]

The article discusses the research on the design of perovskite and silicon heterojunction tandems to improve the electric power conversion efficiency of photovoltaic cells. Topics discussed include contact resistance in titanium dioxide (TiO2)/ perovskite-silicon heterojunction, atomic layer deposition and annealing of TiO2 films and the removal of conventional interlayer in cells.