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.

Here, we report gas-quenched quasi-2D (GA)(MA)(5)Pb5I16 perovskites for single junction solar cells and monolithic-silicon tandem solar cells. This is the first time quasi-2D (GA)(MA)(5)Pb5I16 perovskite cells have been tested with proton beams, showing excellent tolerance. A representative tandem cell also passed the IEC 61215 Thermal Cycling Test (-40 degrees C <-> 85 degrees C) twice, retaining 95.0% of its initial PCE after 400 cycles.

Metal halide perovskite solar cells have achieved tremendous progress and have attracted enormous research and development efforts since the first report of demonstration in 2009. Due to fabrication versatility, many heat treatment methods can be utilized to achieve perovskite film crystallization. Herein, 10.6 mu m carbon dioxide laser process is successfully developed for the first time for perovskite film crystallization. In addition, this is the first time formamidinium lead triiodide solar cells by laser annealing under ambient are demonstrated. The champion cell produces a power conversion efficiency of 21.8%, the highest for laser-annealed perovskite cells. And this is achieved without any additive, passivation, or post-treatment.

Perovskite whentandemed with organic photovoltaics (OPV) for double-junctions have efficiencypotentials over 40%. However, there is still room for improvement suchas better current matching, higher fill factor, as well as lower voltage and fill factor losses in the top perovskite cell. Here weaddress the issue associated with the top perovskite cell by utilising anovel halogenated polycyclic aromatic hydrocarbon compound, 1-naphthylammoniumchloride (NA & horbar;Cl) playing dual roles of surface modification for the hole selectivelayer (HSL) and passivation of HSL/perovskiteinterface. Results of X-ray photoelectron spectroscopy and density functionaltheory calculations reveal that NA & horbar;Cl retains self-assembly property for the HSLwhile demonstrating high dipole moment and polarizability. This induces asurface dipole at the HSL/perovskite interface reducing the energetic barrierfor hole extraction by 210 meV thereby enhancing voltage output and fill factorof the device. Such scheme when implemented in a high bandgap (1.78 eV)perovskite solar cell, results in a respectable efficiency of 19.7% and thehighest fill factor of 85.4% amongst those of 1.78 eV perovskite cells reported.We have also achieved 23% cell efficient monolithic perovskite-OPV tandem withan impressive fill factor of 84%, which is the highest for perovskite-OPVtandem cells reported to-date.

C60 is a widely used electron selective material for p-i-n perovskite cells, however, its energy level does not match well with that of a wide-bandgap perovskite, resulting in low open-circuit voltage (VOC) and fill factor (FF). To overcome this issue, ultra-thin LiF has been widely used as an interlayer between C60 and perovskite layers facilitating efficient electron extraction but resulting in instability. In this work, the use of a piperidinium bromide (PpBr) is reported as an interlayer between C60 and perovskite, and the interlayer further is optimized by introducing an additional oxygen atom on the opposite side of the NH2+. This results in morpholinium bromide (MLBr) with increased dipole moment. Because of this, MLBr is highly effective in minimizing the energy band mismatch between perovskite and C60 layer for electron extraction while at the same time passivating defects. The champion single junction 1.67 eV MLBr solar cell produced a PCE of 21.9% and the champion monolithic MLBr perovskite-Si tandem cell produced a PCE of 28.8%. Most importantly, both encapsulated MLBr and PpBr devices retain over 97% of their initial efficiency after 400 thermal cycles (between -40 and 85 degrees C), twice the number of cycles specified by the International Electrotechnical Commission (IEC) 61215 photovoltaic module standard. A dipole interlayer such as morpholinium bromide (MLBr) between C60 and a 1.67 eV perovskite layer is effective in defect passivation and energy band alignment for charge extraction. Champion single junction and 1 cm2 perovskite-Si tandem devices produced PCE's of 21.9% and 28.8%, respectively. Encapsulated tandems demonstrated excellent stability under continuous 1 sun illumination for 1000 h and retained 97% of initial PCE after 400 thermal cycles test (between -40 and 85 degrees C), twice the length of the IEC61215 Thermal Cycling test standard. image

An ultra-thin indium tin oxide interlayer design was developed for interfacing perovskite solar cells with Si solar cells thereby minimising shunting effects for large area monolithic tandem devices.

State-of-the-art perovskite-perovskite tandem solar cells incorporate a water-based poly(3,4-ethylenedioxythiophene):polystyrenesulfonate (PEDOT:PSS) hole transport layer in its low bandgap subcell. However, there is a limitation regarding its use due to the moisture sensitivity of perovskites and the insulating property of PSS. Here, we overcome the limitation by using a water-free and PSS-free PEDOT-based hole transport layer for low bandgap single-junction perovskite solar cells and in perovskite-perovskite tandems. The champion tandem cell produces an efficiency of 21.5% and a fill factor of 85.8%, the highest for any perovskite-based double-junction tandems. Results of photoelectron spectroscopy, Fourier-transform infrared spectroscopy, and conductive atomic force microscopy reveal evidence of enhanced conductivity of water-free and PSS-free PEDOT compared to its conventional counterpart. The use of water-free and PSS-free PEDOT also eliminates decomposition of high bandgap subcell with its interfacing layer stack in a tandem that otherwise occurs with conventional PEDOT:PSS. This leads to enhanced reproducibility of perovskite-perovskite tandems.

The drastic reduction in launch and manufacturing costs of space hardware has facilitated the emergence of "commercial" space. Radiation‐hard organometal halide perovskite solar cells (PSCs) with low‐cost and high‐efficiency potentials are promising for space applications.High‐efficiency PSCs are tested with different hole transport materials (HTMs) and dopants on 175µm sapphire substrates under 7MeV‐proton‐irradiation‐tests at accumulated fluences of 10 11 , 10 12 , and 10 13 protons cm −2 . While all cells retain >90% of their initial power conversion efficiencies (PCEs) after 10 11 protons cm −2 irradiation, PSCs that have tris(pentafluorophenyl)borane (TPFB) as the HTM dopant and poly[bis(4‐phenyl)(2,5,6‐trimethylphenyl) amine (PTAA) or PTAA:C8BTBT (C8BTBT = 2,7‐Dioctyl[1]benzothieno[3,2‐b][1]benzothiophene) as the HTM are more tolerant to higher‐fluence radiation than their counterparts with the lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) dopant and the 2,2′,7,7′‐Tetrakis[N,N‐di(4‐methoxyphenyl)amino]‐9,9′‐spirobifluorene (Spiro‐OMeTAD) HTM. Radiation induces fluorine diffusion from the LiTFSI dopant toward the perovskite absorber (confirmed by depth‐resolved X‐ray photoelectron spectroscopy) introducing defects. Radiation‐induced defects in cells with the TPFB dopant instead are different and can be “annealed out” by thermal vacuum resulting in PCE recovery. This is the first report using thermal admittance spectroscopy and deep‐level transient spectroscopy for defect analyses on proton‐irradiated and thermal‐vacuum‐recovered PSCs. The insights generated are expected to contribute to efforts in developing low‐cost light‐weight solar cells for space applications.

While many state-of-the-art perovskite solar cells (PSCs) have been realized on rigid glass substrates, demonstrating perovskite cells on other types of surfaces may give rise to new applications. Here, we successfully demonstrate efficient PSCs on steel. The role of an indium tin oxide interlayer as a barrier against iron diffusion from the steel substrate is elucidated. We further show that the performance of the perovskite device on steel can be improved by using an n-octylammonium bromide passivation layer, achieving a power conversion efficiency of 17.1%. To the best of our knowledge, this is the highest reported for perovskite cells on steel. This work demonstrates the robust design necessary for PSCs on steel and the versatility of PSCs. It may also inspire work on other types of surfaces beyond glass, paving the way for a wider range of applications.

We report a metric for evaluating the total efficiency of incident sunlight conversion by solar windows into useful energy in the form of electric power and luminous flux. The transmitted luminous flux is converted into an equivalent energy flux using the luminous efficacy. If the light meets a white light criterion, the luminous efficacy is for ideal white light. Otherwise, it is for light at photopic maximum. The total equivalent energy efficiency metric is formed by adding the equivalent luminous power to the electrical power and dividing the sum by input power. The metric can be used for both global and diffuse incident sunlight. There are two “sweet spots” for efficiency limits as a function of band gap: 1.3 and 2.5 eV. Evaluation of demonstrated semi-transparent perovskite solar cells as an example against the metric follows these predicted trends. The value of spectrum shifting for enhancing total equivalent energy efficiency, especially under diffuse sunlight, can also be quantified. The use of the new efficiency metric will encourage progress in building-integrated photovoltaics by enabling product comparison in terms of their efficiency of energy usage.

In this work, a novel carbazole-based SAM (Ph-2PACz) was developed for facilitating efficient hole extraction and suppressing carrier recombination in high-band-gap (1.67 eV) perovskites for single junction and tandem-cell demonstrations. The champion 21.3% efficient 1.67 eV cell produced a high fill factor (FF) of 82.6% and an open-circuit voltage (VOC) of 1.26 V, representing low band-gap voltage offset at 0.41 V. When Ph-2PACz was applied to the top perovskite cell for a monolithic perovskite-Si tandem, a PCE of 28.9% (on 1 cm2) and a VOC of 1.91 V were obtained. When encapsulated, a tandem cell demonstrated excellent stability under continuous 1 sun illumination (680 h) and damp heat (280 h at 85 degrees C + 85% relative humidity) and passed the International Electrotechnical Commission (IEC) 61215 thermal cycling (200 cycles between -40 degrees C and 85 degrees C) test, retaining 98.8% of the initial PCE.

The rapid progress in space exploration, mining, and tourism has been fuelled by both public and private sector investments. The latter has led to the need to reduce manufacturing and launch cost of space hardware to create a competitive and sustainable space economy. A major step in making space accessible is to develop affordable power systems for “commercial space” use. Photovoltaics has in the past and will in the future be a key component. Metal halide perovskite solar cells show the greatest potential of all emerging technologies for low‐cost space photovoltaics. They have demonstrated the highest rate of power conversion efficiency improvement. Compared to the triple junction III–V compound semiconductor cells commonly used for space applications, perovskite cells have a higher power to weight ratio and are significantly cheaper to be manufactured. They have high radiation tolerance and can be fabricated onto flexible substrates for expand‐on‐demand solar panels. This paper outlines the major space markets for photovoltaics, and research and development opportunities for perovskite space solar cells in the context of their recent progress.

2D Perovskites Cs2Pb(SCN)2Br2, an inorganic-cation pseudo-halide 2D phase perovskite single crystal, is grown by a simple antisolvent vapor-assisted crystallization method, as reported by Chu-Chen Chueh, Anita W. Y. Ho-Baillie, and co-workers in article number 2104782. Cs2Pb(SCN)2Br2 exhibits a reversible first-order phase transformation to CsPbBr2 at 450 K and has a low exciton binding energy amongst the 2D perovskites. Demonstration for photodetector application shows respectable responsivity and detectivity.

High bandgap perovskite solar cells are integral to perovskite‐based multi‐junction tandem solar cells with efficiency potentials over 40%. However, at present, high bandgap perovskite devices underperform compared to their mid bandgap counterparts in terms of voltage outputs and fill factors resulting in lower than ideal efficiencies. Here, the low fill factor aspect of high bandgap perovskite is addressed by developing a cation‐diffusion‐based double‐sided interface passivation scheme that simultaneously provides bulk passivation for a 1.75 eV perovskite cell that is also compatible with a p‐i‐n cell architecture. The champion cell achieves a record fill factor of 86.5% and a power conversion efficiency of 20.2%. Results of ionic distribution profiling, Fourier transform infrared spectroscopy, and X‐ray diffraction crystallography reveal evidence of cation diffusion from the surface perovskite passivation layer into bulk. The diffused cations reduce Shockley–Read–Hall recombination in the perovskite bulk and at the surfaces with the latter being more dominant as confirmed by light‐intensity dependent and temperature‐dependent open‐circuit voltage measurements as well as thermal admittance spectroscopy. This concurrent bulk and surface passivation scheme renders record fill factor and efficiency in the double‐side passivated cells. This provides new insights for future passivation strategies based on ionic diffusion of functionalized materials.

Perovskite solar cells have attracted tremendous research and development activity in recent years due to their excellent optoelectronic material properties and ease of fabrication. They are uniquely attractive for building-integrated photovoltaics (BIPVs) due to their potential to add value in terms of aesthetics. Here, we review the demonstrations of perovskite solar cells suitable for window applications, focusing on their unique advantages associated with transparency control and color control, both statically and dynamically. Our calculations show that the relationship between power conversion efficiency and visible transparency is not strictly linear. Respectable power conversion efficiency (6%–14%) with high (e.g., 90%–100%) visible transparency is theoretically possible. Perovskite cells also produce higher power conversion efficiencies under low-intensity and diffuse light, making them promising for vertical facades. Reported field testing and cost analysis are also summarized. Under each section, research and development opportunities for the widespread implementation of perovskite-based solar windows are presented.

To reduce the reliance on fossil fuel, H 2 , as a clean fuel, has attracted substantial research and development activities in recent years. The traditional water splitting approach requires an applied bias of more than 1.5 V and the use of ion‐selective membranes to prevent the formation of a potentially explosive H 2 –O 2 gas mixture, resulting in increased cost and system design complexity. Here, a solar‐driven H 2 production process requiring a much lower applied bias of 1.05 V is reported whereby aniline (ANI) is oxidized to polyaniline (PANI) at the anode with a yield of 96% and H 2 evolution reaction occurs at the cathode with a faradaic efficiency of 98.6 ± 3.9%. The process has multiple advantages including the elimination of ion‐exchange membrane as PANI is a solid product that also is of substantially higher value than O 2 . For demonstration, a single junction perovskite solar cell and low‐cost earth abundant CoP catalyst are successfully applied for this process. This process contributes to the advancement of solar‐driven low‐cost H 2 generation coupled with co‐production of a high‐value product expediting the transition to a hydrogen economy.

This work reports strategies for improving the power conversion efficiency (PCE) by capitalizing on temporal changes through the storage effect and immediate improvements by interface passivation. It is demonstrated that both strategies can be combined as shown by PCE improvement in passivated perovskite solar cells (PSCs) upon ambient storage because of trap density reduction. By analyzing the dominant charge recombination process, we find that lead-related traps in perovskite bulk, rather than at the surface, are the recombination centers in both as-fabricated and ambient-stored passivated PSCs. This emphasizes the necessity to reduce intrinsic defects in the perovskite bulk. Furthermore, storage causes temporal changes in band alignment even in passivated PSCs, contributing to PCE improvement. Building on these findings, composition engineering was employed to produce further immediate PCE improvements because of defect reduction in the bulk, achieving a PCE of 22.2%. These results show that understanding the dominant recombination mechanisms within a PSC is important to inform strategies for producing immediate and temporal PCE enhancements either by interface passivation, storage, composition engineering, or a combination of them all to fabricate highly efficient PSCs.

The power conversion efficiency (PCE) of metal halide perovskite solar cells (PSCs) has improved dramatically from 3.8% to 25.5% in only a decade. Gas quenching is a desirable method for fabricating high-efficiency cells as it does not consume antisolvents and is compatible with large-area deposition methods such as doctor blading and slot-die coating. To further improve PCEs for gas-quenched PSCs, here, we develop complementary bulk and surface passivation strategies by incorporating potassium iodide (KI) in the perovskite precursor and applying n-hexylammonium bromide (HABr) to the perovskite surface. We show that (1) KI induces a spatial-compositional change, improving grain boundary properties; (2) KI and HABr reduce traps, especially at levels close to the mid-gap; and (3) HABr greatly improves the built-in potential of the device, thereby improving voltage output. The champion device achieves a steady-state PCE of 23.6% with a V-OC of 1.23V, which is, to the best of our knowledge, the highest for PSC by gas quenching to date.

The power conversion efficiency (PCE) of solution-processed organic-inorganic mixed halide perovskite solar cells has achieved rapid improvement. However, it is imperative to minimize the voltage deficit (W-oc = E-g/q - V-oc) for their PCE to approach the theoretical limit. Herein, the strategy of depositing homologous bromide salts on the perovskite surface to achieve a surface and bulk passivation for the fabrication of solar cells with high open-circuit voltage is reported. Distinct from the conclusions given by previous works, that homologous bromides such as FABr only react with PbI2 to form a large-bandgap perovskite layer on top of the original perovskite, this work shows that the bromide also penetrates the perovskite film and passivates the perovskite in the bulk. This is confirmed by the small-bandgap enlargement observed by absorbance and photoluminescence, and the bromide element ratio increasing in the bulk by time-of-flight secondary-ion mass spectrometry and depth-resolved X-ray photoelectron spectroscopy. Furthermore, a clear suppression of non-radiative recombination is confirmed by a variety of characterization methods. This work provides a simple and universal way to reduce the W-oc of single-junction perovskite solar cells and it will also shed light on developing other high-performance optoelectronic devices, including perovskite-based tandems and light-emitting diodes.