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The popularity of metal halide perovskites is in part the result of their versatility in numerous applications. To date, perovskites are used in their intrinsic, undoped form, as the doping of these materials is not yet adequately mastered. Herein, the recently reported electronic doping of CH3NH3PbI3 is employed to fabricate perovskite solar cells in which the interfacial electron transport layer (ETL) is replaced by n‐doping of one side of the perovskite film. The doping involves the incorporation of metastable Sm2+ ions that undergo an in situ oxidation to Sm3+, releasing electrons to the conduction band to render the perovskite n‐type. In spite of the lack of an ETL, these solar cells have the same efficiency as the samples with the ETL. The open circuit voltage of the doped solar cells increases proportionally to the doping concentration due to the narrowing of the depletion layer thickness at the interface of the perovskite and the top electrode, reaching the value of ≈1 V for the doped ETL‐free device, the same as for the reference sample. These proof‐of‐concept results represent the first step toward perovskite‐based devices incorporating a p‐n homojunction. [ABSTRACT FROM AUTHOR]

Due to the unique microstructure of hydrogenated nanocrystalline silicon oxide (nc‐SiOx:H), the optoelectronic properties of this material can be tuned over a wide range, which makes it adaptable to different solar cell applications. In this work, the authors review the material properties of nc‐SiOx:H and the versatility of its applications in different types of solar cells. The review starts by introducing the growth principle of doped nc‐SiOx:H layers, the effect of oxygen content on the material properties, and the relationship between optoelectronic properties and its microstructure. A theoretical analysis of charge carrier transport mechanisms in silicon heterojunction (SHJ) solar cells with wide band gap layers is then presented. Afterwards, the authors focus on the recent developments in the implementation of nc‐SiOx:H and hydrogenated amorphous silicon oxide (a‐SiOx:H) films for SHJ, passivating contacts, and perovskite/silicon tandem devices. [ABSTRACT FROM AUTHOR]

With the aid of 3D full‐field finite difference time–domain simulations, model configurations for CsPbI3$\left(\text{CsPbI}\right)_{3}$ thin‐film solar cell devices that include periodically arranged TiO2$\left(\text{TiO}\right)_{2}$ microspheres, exhibiting resonating whispering gallery modes (WGMs), are proposed. The TiO2$\left(\text{TiO}\right)_{2}$ microspheres present, either immersed in perovskite or coated with perovskite layer, between the electron‐ and hole‐transport layers show enhanced current‐conversion efficiency. The presence of WGMs lead to enhancement in the absorption of CsPbI3$\left(\text{CsPbI}\right)_{3}$ layer. The incoming electromagnetic wave couples with TiO2$\left(\text{TiO}\right)_{2}$ microsphere and forms confined resonating modes. Different designs are examined for deciding the appropriate position of WGM exhibiting spheres with respect to thin‐film perovskite solar cell (PSC) featuring back reflector and optimized antireflectance coating. Since the incoupling element is lossless, energy stored in microspheres is absorbed efficiently by the underlying active material. This directly contributes to the increment in the current density of the solar cell. Thus, the devices show a higher current density of 23.62 mA cm−1, while that in planar solar cell device shows current density of 13.68 mA cm−1, for the same thickness of perovskite layer. This leads to more than 70% enhancement in the short‐circuit current density than the conventional PSCs device of similar size. [ABSTRACT FROM AUTHOR]

The frequency response of the photocurrent (Iph) generated in perovskite photodetectors is a crucial issue in imaging or telecommunication applications, although it is briefly discussed in the literature. The present work obtains for the first time the complete expression of the Iph generated on MAPbI3 (MA:methylamoniumI) perovskite polycrystalline thin films. A conditioning circuit is used to extract Iph at 1 V of bias voltage under a square‐modulated laser excitation with a sensitivity smaller than 1 nW and a linear dynamic range LDR > 200 dB; It allows an accurate determination of the module of Iph together with the phase, which is not usually reported in photodetector systems. The frequency domain analysis reveals that Iph can be modeled by two fractional poles located at low (10 kHz) and high (39–250 kHz) cut‐off frequencies. Optimum geometrical parameters and excitation fluence are found for the wider response, resulting for the best device on a cut off frequency up to 250 kHz, and the reproduction of square‐modulated optical waves up to 100 kHz. These results represent an important strategy toward the electrical analysis of MAPbI3 (or other perovskite materials) for the design of posterior electronic stages, optimization of devices and determination of their figures of merit. [ABSTRACT FROM AUTHOR]

The reliability of oxide‐semiconductor (OS) thin‐film transistors (TFTs) is significantly influenced by the gate insulator (GI). During electrical bias stress, the defect sites near the semiconductor/GI interface and/or within the GI may trap electrons, which makes the threshold voltage (Vth) shift toward positive values. On the other hand, carbon (C) or hydrogen (H) atoms may diffuse from the GI into the active layer, and act as shallow donors, which induce negative Vth shifts (ΔVth). In this paper, an in situ atomic layer deposition (ALD)‐based GI heterostructure is introduced, which consists of a stack of two complementary materials, namely Al2O3 and SiO2. Here, a competition occurs between electron trapping in Al2O3 (positive ΔVth) and carrier generation from H atoms in SiO2 (negative ΔVth) which allows the achievement of nearly zero ΔVth under positive bias temperature stress (PBTS). This strategy is successfully applied to a high‐mobility (>50 cm2 Vs−1) ALD‐based indium‐gallium‐zinc oxide (IGZO) device, resulting in a net ∆Vth of −0.02 V under PBTS and drain current variation (∆ID) of +0.49% under constant current stress (CCS). The application of an in situ ALD process thus offers valuable insights to resolve the mobility versus reliability trade‐off in high‐performance oxide TFTs. [ABSTRACT FROM AUTHOR]

Tunable bandgaps make halide perovskites promising candidates for developing tandem solar cells (TSCs), a strategy to break the radiative limit of 33.7% for single‐junction solar cells. Combining perovskites with market‐dominant crystalline silicon (c‐Si) is particularly attractive; simple estimates based on the bandgap matching indicate that the efficiency limit in such tandem device is as high as 46%. However, state‐of‐the‐art perovskite/c‐Si TSCs only achieve an efficiency of ~32.5%, implying significant challenges and also rich opportunities. In this review, we start with the operating mechanism and efficiency limit of TSCs, followed by systematical discussions on wide‐bandgap perovskite front cells, interface selective contacts, and electrical interconnection layer, as well as photon management for highly efficient perovskite/c‐Si TSCs. We highlight the challenges in this field and provide our understanding of future research directions toward highly efficient and stable large‐scale wide‐bandgap perovskite front cells for the commercialization of perovskite/c‐Si TSCs. [ABSTRACT FROM AUTHOR]

Halide perovskites, in the form of thin films and colloidal nanocrystals, have recently taken semiconductor optoelectronics research by storm, and have emerged as promising candidates for high‐performance solar cells, light‐emitting diodes (LEDs), lasers, photodetectors, and radiation detectors. The impressive optical and optoelectronic properties, along with the rapid increase in efficiencies of solar cells and LEDs, have greatly attracted researchers across many disciplines. However, most advances made so far in terms of preparation (colloidal nanocrystals and thin films), and the devices with highest efficiencies are based on Pb‐based halide perovskites, which have raised concerns over their commercialization due to the toxicity of Pb. This has triggered the search for lower‐toxicity Pb‐free halide perovskites and has led to significant progress in the last few years. In this roadmap review, researchers of different expertise have joined together to summarize the latest progress, outstanding challenges, and future directions of Pb‐free halide perovskite thin films and nanocrystals, regarding their synthesis, optical spectroscopy, and optoelectronic devices, to guide the researchers currently working in this area as well as those that will join the field in the future. [ABSTRACT FROM AUTHOR]

Photocurrent matching in conventional monolithic tandem solar cells is achieved by choosing semiconductors with complementary absorption spectra and by carefully adjusting the optical properties of the complete top and bottom stacks. However, for thin film photovoltaic technologies at the module level, another design variable significantly alleviates the task of photocurrent matching, namely the cell width, whose modification can be readily realized by the adjustment of the module layout. Herein, this concept is demonstrated at the experimental level for the first time for a 2T‐mechanically stacked perovskite (FAPbBr3)/organic (PM6:Y6:PCBM) tandem mini‐module, an unprecedented approach for these emergent photovoltaic technologies fabricated in an independent manner. An excellent Isc matching is achieved by tuning the cell widths of the perovskite and organic modules to 7.22 mm (PCEPVKT‐mod = 6.69%) and 3.19 mm (PCEOPV‐mod = 12.46%), respectively, leading to a champion efficiency of 14.94% for the tandem module interconnected in series with an aperture area of 20.25 cm2. Rather than demonstrating high efficiencies at the level of small lab cells, this successful experimental proof‐of‐concept at the module level proves to be particularly useful to couple devices with non‐complementary semiconductors, either in series or in parallel electrical connection, hence overcoming the limitations imposed by the monolithic structure. [ABSTRACT FROM AUTHOR]

Tandem solar cells are rationally designed and fabricated by stacking multiple subcells to achieve power conversion efficiency well above the Shockley‐Queisser (SQ) limit. There is a large selection pool for the subcell candidates, such as Si, III–V, Kesterite, Perovskite, and organic solar cells. A series of different combinations of these subcells have been successfully demonstrated in practical tandem solar cell devices. However, there has not been a systematic summary of how to connect subcells in a tandem solar cell using a practical, cost‐effective, and efficiency‐beneficial fashion. In this work, the connection manners of subcells within a tandem cell are classified into three main categories, performing sequential growth, using the physical connection, and applying an intermediate layer, focusing on systematical description of intermediate layers using different materials. The advantages and disadvantages of these connection methods and their applicability to tandem cell types are further elaborated using two typical example models, III–V/Si and Perovskite inclusive tandem cell devices. Eventually, this work can provide useful guidance on how to carry out a suitable intermediate connection in the design of tandem solar cells depending on the selected subcells and device structure. [ABSTRACT FROM AUTHOR]

Recently, multijunction tandem solar cells (TSCs) have presented high power conversion efficiency and revealed their immense potential in photovoltaic evolution. It is demonstrated that multiple light absorbers with various bandgap energies overcome the Shockley–Queisser limit of single‐junction solar cells by absorbing the wide‐range wavelength photons. Here, the main key challenges are reviewed, especially the charge carrier dynamics in perovskite‐based 2‐terminal (2‐T) TSCs in terms of current matching, and how to manage these issues from a vantage point of characterization. To do this, the effect of recombination layers, optical and fabrication hurdles, and the impact of wide bandgap perovskite solar cells are discussed extensively. Afterward, this review focuses on various optoelectronics, spectroscopic, and theoretical (optical simulation) characterizations to figure out those issues, especially current‐matching issues faced by the photovoltaic society. This review comprehensively provides deep insights into the relationship between the current‐matching problems and the photovoltaic performance of TSCs through a variety of perspectives. Consequently, it is believed that this review is essential to address the main problems of 2‐T TSCs, and the suggestions to elucidate the charge carrier dynamics and its characterization may pave the way to overcome such obstacles to further improve the development of 2‐T TSCs in relation to the current‐matching problems. [ABSTRACT FROM AUTHOR]

Multi‐absorbers, and tandem solar cells (TSCs), have enticed research focus with their competitive advantage of crossing the limits posed by Shockley–Queisser efficiency by single‐junction solar cell (SC). Perovskite solar cells (PSC) with their bandgap tunability and ease of solution processing at low temperatures for securing high efficiency (25.8%) provide an ideal candidate for top cell in TSC. Simultaneously, Si SCs with a 95% market share and their ideal low bandgap (1.12 eV) for capturing high‐energy photons in the near‐infrared (NIR) can assume bottom cell in TSC. This review highlights the research perspective for perovskite/Si TSCs to expedite its emergence as future TSC. The 4T device architecture of perovskite/Si TSC optically couples the subcells whereas the 2T configuration ensures the optical and electrical coupling among the constituent subcells. The semitransparency of the top cell, flat as well as textured Si bottom cell, matching of the current between the subcell through the recombination and tunnel junction layers, and modification of perovskites through‐thickness variation are few worth‐considering factors that contribute toward highly efficient perovskite/Si TSC. Finally, the research insight about perovskite/Si and all‐perovskite TSC is analyzed with reference to the ideal choice for the bottom cell. [ABSTRACT FROM AUTHOR]

Flexible perovskite solar cells (f‐PSCs) as a promising power source have grabbed surging attention from academia and industry specialists by integrating with different wearable and portable electronics. With the development of low‐temperature solution preparation technology and the application of different engineering strategies, the power conversion efficiency of f‐PSCs has approached 24%. Due to the inherent properties and application scenarios of f‐PSCs, the study of strain in these devices is recognized as one of the key factors in obtaining ideal devices and promoting commercialization. The strains mainly from the change of bond and lattice volume can promote phase transformation, induce decomposition of perovskite film, decrease mechanical stability, etc. However, the effect of strain on the performance of f‐PSCs has not been systematically summarized yet. Herein, the sources of strain, evaluation methods, impacts on f‐PSCs, and the engineering strategies to modulate strain are summarized. Furthermore, the problems and future challenges in this regard are raised, and solutions and outlooks are offered. This review is dedicated to summarizing and enhancing the research into the strain of f‐PSCs to provide some new insights that can further improve the optoelectronic performance and stability of flexible devices. [ABSTRACT FROM AUTHOR]

Besides further improvement in the power conversion efficiency (PCE) of perovskite solar cells (PSC), their long‐term stability must also be ensured. Additives such as organic cations with halide counter anions are considered promising candidates to address this challenge, conferring both higher performance and increased stability to perovskite‐based devices. Here, a stabilizing additive (N,N‐dimethylmethyleneiminium chloride, [Dmmim]Cl) is identified, and its effect on charge carrier mobility and lifetime under thermal stress in triple cation perovskite (Cs0.05MA0.05FA0.90PbI3) thin films is investigated. To explore the fundamental mechanisms limiting charge carrier mobility, temperature‐dependent microwave conductivity measurements are performed. Different mobility behaviors across two temperature regions are revealed, following the power law Tm, indicating two different dominant scattering mechanisms. The low‐temperature region is assigned to charge carrier scattering with polar optical phonons, while a strong decrease in mobility at high temperatures is due to dynamic disorder. The results obtained rationalize the improved stability of the [Dmmim]Cl‐doped films and devices compared to the undoped reference samples, by limiting temperature‐activated mobile ions and retarding degradation of the perovskite film. [ABSTRACT FROM AUTHOR]

Conventional semi‐transparent perovskite solar cells (ST‐PSCs) generally exhibit inferior performance and stability relative to opaque PSCs. However, a comprehensive understanding of the origins of inferior performance and stability of ST‐PSCs and a practical solution to these challenges are both lacking. Here, it is shown for the first time that lithium ions from a lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)‐doped 2,2′,7,7′‐tetrakis[N,N‐di(4‐methoxyphenyl)amino]−9,9′‐spirobifluorene (Spiro‐MeOTAD) hole‐transport layer (HTL) can diffuse into the molybdenum trioxide buffer layer at their interface, yielding ST‐PSCs with lower efficiency and accelerated degradation. It is also demonstrated that this undesired Li‐ion diffusion can be avoided by HTL surface modification with stable lithium oxides. Using this approach, the constructed ST‐PSC exhibits a new record power conversion efficiency (PCE) of 22.02% (21.68% certified) and a fill factor of >80%, with >99% shelf‐stability after 400 h and >99% operational stability for 240 h, which clears away this longstanding limitation of the performance and stability of ST‐PSCs. This strategy is also applied to fabricate four‐ and two‐terminal perovskite/silicon tandem solar cells with bifacial equivalent efficiencies of 31.5% and 26.34%, respectively, at 20% albedo. [ABSTRACT FROM AUTHOR]

Organic‐inorganic hybrid perovskite (MAPbX3) is known having excellent photoelectric properties. Compared to polycrystalline films, perovskite micro/nanowires can provide improved optoelectronic properties, mechanical flexibility, and adaptability due to higher crystallinity. However, their economical, scalable, and controllable fabrication remains a challenge. In this work, the authors report a facile way to fabricate high‐quality MAPbX3 triangular‐micro‐wires (TMWs). The Si/SiO2 substrate with triangular‐micro‐trenches (TMTs) array serves as the template for the growth of MAPbX3 TMWs array through blade coating. The MAPbX3 TMW first nucleated at the trench bottom, which facilitating the nanowire growth with high crystallinity. In addition, the size and periodicity of TMTs array can be independently controlled, providing potential for scale‐up device applications. The photodetectors fabricated with these MAPbI3 TMWs show excellent responsivity of (144.5 ± 2.1) A/W and specific detectivity of (2.7 ± 0.02) × 1011 Jones under weak light (0.5 µW cm−2). Their photoresponse to pulsed light is stable and reproducible, with rise and decay times of 7.5 and 6.0 ms, respectively. Finally, with the demonstration of the image sensor application, MAPbX3 TMWs array is anticipated to be suitable for large‐area, high‐performance integrated optoelectronics. [ABSTRACT FROM AUTHOR]

Perovskite light‐emitting diodes (PeLEDs) are promising candidates for lighting and display applications. However, perovskites usually have a relatively high refractive index compared to organic semiconductors, causing a lower optical efficiency due to a narrower escape cone. In this work, the theoretical analysis shows that the microcavity effect enables PeLEDs to achieve a light extraction efficiency of 51%, much higher than the ≈20% estimated by the classical theory. Besides the interference in the microcavity, the efficiency improvement is also attributed to the low surface plasmon loss and a high ratio of horizontal dipoles under the Purcell effect. In a microcavity PeLED, a horizontal dipole shows three times the improvement in the Purcell factor of a vertical dipole, making the horizontal dipole with high efficiency contribute 86% of light output. Moreover, the experiment shows that the microcavity can increase the external quantum efficiency by 70%. A narrower spectrum and shorter photoluminescence lifetime are also observed. These phenomena are attributed to the simultaneous enhancement of light extraction efficiency and internal quantum efficiency. This work reveals the importance of microcavity design and provides guidance to break through the classical efficiency limit and achieve high‐efficiency PeLEDs. [ABSTRACT FROM AUTHOR]

The photodecomposition of PbI2 in the perovskite halide structure has been identified as a primary reason for the rapid degradation of metal halide perovskite solar cells (PSCs) under continuous illumination. In particular, excess PbI2 on the surface of perovskite films reduces the stability of PSCs via several mechanisms that are still unelucidated. Herein, the influence of excess PbI2 on PSCs is investigated by varying the Au deposition rate, which results in different temperatures during the fabrication of PSCs, and then they are compared with stoichiometric PSCs. It is demonstrated that the anion exchange of Br− in perovskite and I− in excess PbI2 occurs at the grain boundary and interface of the perovskite layers induced by the high heating temperature, leading to a photoluminescence peak redshift and lower power conversion efficiency. Light illumination accelerates the exchange of Br− and I− between the perovskite layer and excess PbI2 induced by carrier accumulation at the interface and grain boundary, leading to the poor stability of the PSCs. [ABSTRACT FROM AUTHOR]

Among all‐inorganic perovskites, CsPbIBr2 has become a potential candidate in semitransparent perovskite solar cells (ST‐PSCs) due to its excellent thermal stability and suitable bandgap. Herein, by optimizing the ambient temperature in an N2‐filled glovebox, the growth process of CsPbIBr2 crystals is regulated to avoid the generation of pinholes and improve the photoelectric conversion capacity of perovskite cells. When the ambient temperature is around 25 °C, the champion power conversion efficiency (PCE) of 10.82% with opaque n–i–p structure is achieved. Based on MoOx/Ag/MoOx (20/12/20 nm) multilayer top electrode, the ST‐PSC device achieves a maximum PCE of 7.06% at the fluorine‐doped tin oxide side under the simulated 1 sun illumination condition and a PCE of 23.96% at MoOx/Ag/MoOx electrode side under the intensity of 1000 lux (≈350 μW cm−2) provided by a white light‐emitting diode lamp, along with an average visible transmittance of 29.25%. The resulting perovskite solar cell is the first bifacial inorganic ST‐PSC that could be used under both sunlight and indoor light, which is an important step toward all‐day power generation of inorganic ST‐PSCs and building‐integrated photovoltaics. [ABSTRACT FROM AUTHOR]

Energetics at the carrier selective layer/absorber interface plays a subtle, yet crucial role in influencing the performance of any photovoltaic technology. This review focuses on the interface energetics and resulting aspects of device physics associated with n‐type molybdenum oxide, which is adopted as a hole selective layer over a diverse class of photovoltaic technologies ranging from silicon heterojunction, organic, and perovskite solar cells. As existing literatures provide a very inconsistent picture of the electronic structure of transition metal oxides, specifically in the case of molybdenum oxide (MoOx), this review makes a first‐of‐its‐kind attempt to connect the scattered reports and thus highlight the ways in which device performance varies for a diverse class of photon absorbers used in conjunction with n‐type MoOx hole selective layer. In spite of the interfacial energy requirements and in turn fundamental working mechanism of varied photovoltaic technologies being the same, an attempt to compare and collate the contributions of MoOx as a charge selective layer for each of these technologies is yet to be done. Herein, the role played by MoOx/absorber interface engineering on the performance of varied photovoltaic technologies, which remains a fundamental and yet unaddressed theme till date, is focused on. [ABSTRACT FROM AUTHOR]

As a more efficient alternative to the crystalline Si (c‐Si) cell whose performance is approaching its theoretical limit, perovskite (PVSK)/Si tandem solar cells (TSCs) are attracting attention from academia and industry. The tandem device, which can benefit from the maturity of the c‐Si cells and the high performance of the PVSK solar cell, has undergone tremendous development. The expectation for its commercialization is increasing as the device shows conversion efficiencies surpassing those of single‐junction solar cells. In this perspective article, the recent progress of the PVSK/Si TSC is summarized from a viewpoint balanced between academia and industry, by regrouping reported devices depending on the types of Si bottom cells: passivated emitter rear contact, heterojunction with intrinsic thin layer, and polysilicon‐passivated contact. In addition, opto‐electronic characterization methods of the PVSK/Si TSCs are reviewed, which can provide an in‐depth analysis of the subcells that can facilitate the development. [ABSTRACT FROM AUTHOR]

Semitransparent photovoltaic (STPV) solar cells offer an immense opportunity to expand the scope of photovoltaics to special applications such as windows, facades, skylights, and so on. These new opportunities have encouraged researchers to develop STPVs using traditional thin‐film solar cell technologies (amorphous‐Si, CdTe, and CIGS or emerging solar cells (organic, perovskites, and dye‐sensitized). There are considerable improvements in both power conversion efficiency (PCE) and semitransparency of these STPV devices. This review studies the device structure of state‐of‐the‐art STPV devices and thereby analyzes the different approaches toward maximizing the product of PCE and average visible transmittance. The origins of PCE losses during the opaque‐to‐semitransparent transition in the different STPV technologies are discussed. In addition, critical practical aspects relevant to all STPV devices, such as compatibility of the top transparent electrode with the device structure, buffer layer optimization, light management engineering, scale‐up, and stability, are also reported. This overview is expected to facilitate researchers across different technologies to identify and overcome the challenges toward achieving higher light utilization efficiencies in STPVs. [ABSTRACT FROM AUTHOR]

The power conversion efficiency (PCE) of organic–inorganic halide perovskite solar cells (PSCs) has increased rapidly in recent years, with the certified best perovskite single‐junction photovoltaics reaching an astounding PCE of 26%. Formamidine (FA)‐based perovskites possess excellent photovoltaic properties and superior thermal stability, establishing them as one of the most promising perovskite materials for light absorption. However, the issue of the phase instability of black‐phase formamidinium lead iodide (α‐FAPbI3) perovskite has seriously impeded its commercialization process, with the strain found in perovskite films being regarded as a significant factor impacting the stability of PSCs. This article begins by examining the sources of strain and the characterization techniques related to perovskites. Subsequently, it outlines the effects of strain on FA‐based perovskites and presents strategies to modify lattice strain. Finally, the potential for strain engineering in the future is discussed. This review aims to clarify the impact of strain on FA‐based perovskite, determine potential methods of strain engineering to enhance device performance, and ultimately facilitate the commercialization of these materials. [ABSTRACT FROM AUTHOR]

Passivating contacts are crucial for realizing high‐performance crystalline silicon solar cells. Herein, contact formation by plasma‐enhanced chemical vapor deposition (PECVD) followed by an annealing step is focused on. Poly‐SiOx passivating contacts by combining plasma‐assisted N2O‐based oxidation of silicon (PANO‐SiOx) with a thin film of phosphorus (n+) or boron (p+)‐doped hydrogenated amorphous silicon oxide (a‐SiOx:H) are manufactured. Postannealing is conducted for transitioning a‐SiOx:H into poly‐SiOx. The aim is to achieve a contact with low absorption and high‐quality passivation. It is demonstrated that by tuning the plasma oxidation process time and power, the PANO‐SiOx thickness and its passivation quality can be controlled. A higher SiO2 content is observed in PANO‐SiOx than in the nitric acid oxidation of silicon (NAOS‐SiOx) counterpart. PANO‐SiOx acts as a stronger diffusion barrier for both boron and phosphorus atoms compared to NAOS‐SiOx, affecting the dopant distribution during annealing. Implied open‐circuit voltages up to 751 and 710 mV for n+ and p+ flat symmetric samples, respectively, are demonstrated. With respect to standard thermally grown SiO2 tunneling oxide combined with (in/ex)situ‐doped low‐pressure chemical vapor deposition poly‐Si, this study presents a simple alternative for manufacturing passivating contact fully based on PECVD processes. [ABSTRACT FROM AUTHOR]

Opto‐electronic models that seek to predict the performance of perovskite and tandem solar cells (PSCs/TSCs) often keep the optical and recombination parameters (ORPs) constant in subsequent studies. During fabrication of PSCs, however, these parameters can vary significantly. To account for the inherent fabrication variability, a comprehensive opto‐electronic‐electric model to predict the current–voltage characteristics of four‐terminal (4T) TSCs is developed. This model is calibrated with forty‐eight in‐house fabricated transparent PSCs with perovskite layer thickness of 420, 550, and 700 nm and corresponding median efficiencies of 20.6%, 21.1%, and 21.0%, respectively; a CIS bottom cell with stand‐alone efficiency of 17.5%; and combined 4T TSCs with a median efficiency of 29.0%. After fitting and validation, the functional forms of the ORPs are captured to estimate how they change with perovskite layer thickness. Finally, the errors with models assuming constant ORPs are demonstrated and how to improve the TSCs efficiency to more than 30% is discussed. [ABSTRACT FROM AUTHOR]

Owing to the bandgap‐bowing effect, mixed lead‐tin halide perovskites provide ideal bandgaps for the bottom subcell of all‐perovskite tandem photovoltaic devices that offer fundamentally elevated power‐conversion efficiencies. However, these materials suffer from degradation in ambient air, which worsens their optoelectronic properties and hinders their usability for photovoltaic applications. Such degradation pathways are not yet fully understood, especially for the perovskites in the middle of the APbxSn1‐xI3 solid solution line, which offer the narrowest bandgaps across the range. This study unravels the degradation mechanisms of APbxSn1‐xI3 perovskites, reporting clear differences between mixed lead‐tin (x = 0.5) and tin‐only (x = 0) perovskites. The dynamic optoelectronic properties, electronic structure, crystal structure, and decomposition products of the perovskite thin films are examined in situ during air exposure. Both perovskite compositions suffer from the formation of defects over the timescale of hours, as indicated by a significant reduction in their charge‐carrier diffusion lengths. For tin‐only perovskite, degradation predominantly causes the formation of energetically shallow tin vacancies and hole doping. However, for mixed lead‐tin perovskite, deep trap states are formed that significantly accelerate charge‐carrier recombination, yet leave mobilities relatively unaffected. These findings highlight the need for passivation strategies tailored specifically to mixed lead‐tin iodide perovskites. [ABSTRACT FROM AUTHOR]

Transparent photovoltaics (TPVs) can be integrated into the surfaces of buildings and vehicles to provide point‐of‐use power without impacting aesthetics. Unlike TPVs that target the photon‐rich near‐infrared portion of the solar spectrum, TPVs that harvest ultraviolet (UV) photons can have significantly higher transparency and color neutrality, offering a superior solution for low‐power electronics with stringent aesthetic tolerance. In addition to being highly transparent and colorless, an ideal UV‐absorbing TPV should also be operationally stable and scalable over large areas while still outputting sufficient power for its specified application. None of today's TPVs meet all these criteria simultaneously. Here, the first UV‐absorbing TPV is demonstrated that satisfies all four criteria by using CsPbCl2.5Br0.5 as the absorber. By precisely tuning the halide ratio during thermal co‐evaporation, high‐quality large‐area perovskite films can be accessed with an ideal absorption cutoff for aesthetic performance. The resulting TPVs exhibit a record average visible transmittance of 84.6% and a color rendering index of 96.5, while maintaining an output power density of 11 W m−2 under one‐sun illumination. Further, the large‐area prototypes up to 25 cm2 are demonstrated, that are operationally stable with extrapolated lifetimes of >20 yrs under outdoor conditions. [ABSTRACT FROM AUTHOR]

Nonradiative decays of surface plasmon (SP) can generate photocarriers in femtosecond, and it therefore has been attracting widespread research attention in ultrafast optoelectronics. Taking advantage of the probe technique, Kelvin probe force microscopy (KPFM) can characterize the spatial distribution of hot carriers in nanoscale and thereby provide necessary analysis for device investigation and engineering. In this work, the behavior of plasmonic hot holes is demonstrated for Ag nanoparticles (NPs) based on the fabrication of CuI hole transport layers. The morphological, optical, and electronic properties of Ag NPs and CuI films are systematically investigated. With the confocal lasers of over‐ and sub‐bandgap wavelength, reversed evolution trends of surface potentials are observed by KPFM, indicating the effective injection of hot holes into CuI valence band (VB). Cross‐verification is also performed based on the fabrication of metal–semiconductor–metal (MSM) photodetectors, and the photoelectrical tests highly dovetail with the surface potential evolution. This research provides an important reference for the plasmonic photoelectronics in both device design and research methods. [ABSTRACT FROM AUTHOR]

Recently, the mixed‐dimensional (3D/2D or 3D/1D) perovskite solar cells using small organic spacers have attracted interest due to their outstanding long‐term stability. Here, a new type of thiophene‐based organic cation 2‐(thiophene‐2yl‐)pyridine‐1‐ium iodide (ThPyI), which is used to fabricate mixed‐dimensional 3D/1D perovskite solar cells, is presented. The ThPyI‐based 1D perovskitoid is applied as a passivator on top of a 3D methyl ammonium lead iodide (MAPI) to fabricate surface‐passivated 3D/1D perovskite films or added alone into the 3D perovskite precursor to generate bulk‐passivated 3D MAPI. The 1D perovskitoid acts as a passivating agent at the grain boundaries of surface‐passivated 3D/1D, which improves the power conversion efficiency (PCE) of the solar cells. Grazing incidence wide‐angle X‐ray scattering (GIWAXS) studies confirm that ThPyI triggers the preferential orientation of the bulk MAPI slabs, which is essential to enhance charge transport. Champion bulk‐passivated 3D and surface‐passivated 3D/1D devices yield 14.10% and 19.60% PCE, respectively. The bulk‐passivated 3D offers favorable stability, with 84% PCE retained after 2000 h without encapsulation. This study brings a new perspective to the design of organic spacers having a different binding motif and a passivation strategy to mitigate the impact of defects in hybrid 3D/1D perovskite solar cells. [ABSTRACT FROM AUTHOR]

After the first visible photoluminescence (PL) from porous silicon (pSi), continuous efforts are made to fabricate Si-based compound nanomaterials embedded in matrices such as oxide, nitride, and carbide to improve optical performance and industrial acceptability. These nanomaterials' functional and desired properties (nanoparticles and quantum dots embedded in matrices) can vary significantly when embedded in technologically relevant matrices. However, exploring the exact emission mechanisms is one of the remaining challenges from the past few decades. To cover this gap, this review discusses the morphological and optoelectronic properties of Si-based compound nanomaterials and their correlation with the quantum confinement effect and different surface states to find precise emission mechanisms. One of the biggest challenges of using silicon nanomaterials in the biological sector is the development of sensitive materials of low/acceptable toxicity for identifying target analytes either inside/outside the biological platforms. In this scenario, silicon-based compound matrices can offer different characteristics and advantages depending on their size configurations and PL emission mechanisms. On the other hand, a proper understanding of these multifaceted silicon nanomaterials' optical properties (emission mechanisms) can be exploited for pathogen detection and in situ applications in cells and tissues, embarking on a new era of bioimaging technology. [ABSTRACT FROM AUTHOR]

Wide bandgap perovskites are being widely studied in view of their potential applications in tandem devices and other semitransparent photovoltaics. Vacuum deposition of perovskite thin films is advantageous as it allows the fabrication of multilayer devices, fine control over thickness and purity, and it can be upscaled to meet production needs. However, the vacuum processing of multicomponent perovskites (typically used to achieve wide bandgaps) is not straightforward, because one needs to simultaneously control several thermal sources during the deposition. Here a simplified dual‐source vacuum deposition method to obtain wide bandgap perovskite films is shown. The solar cells obtained with these materials have similar or even larger efficiency as those including multiple A‐cations, but are much more thermally stable, up to 3500 h at 85 °C for a perovskite with a bandgap of 1.64 eV. With optimized thickness, record efficiency of >19% and semitransparent devices with stabilized power output in excess of 17% are achieved. [ABSTRACT FROM AUTHOR]

Carrier‐selective contact is an essential strategy to improve the power conversion efficiency (PCE) of crystalline silicon (c‐Si) solar cells by enhancing carrier transport and reducing recombination. Many two‐dimensional transition metal carbides/nitrides (MXene) possess excellent electrical conductivity and tunable work function, enabling them as potential carrier‐selective contact materials for c‐Si solar cells. Herein, low work function (3.71 eV) monolayer Ti3C2Tx thin films are fabricated with an ordered arrangement of nanosheets by interfacial self‐assembly method, and the Ti3C2Tx/n‐type c‐Si heterostructure achieves extremely low contact resistivity (22.64 mΩ cm2). Dopant‐free heterojunction crystalline silicon solar cell with self‐assembled monolayer Ti3C2Tx electron‐selective contact is reported for the first time, showing the highest PCE of 16.46% among MXene monolayer‐based c‐Si solar cells, which is mainly attributed to the greatly increased fill factor and open circuit voltage by the accession of self‐assembled monolayer Ti3C2Tx as electron transport layer. This work opens up the possibility of applying MXene as electron transport material for photovoltaic devices. [ABSTRACT FROM AUTHOR]

The unprecedented development of perovskite solar cells (PSCs) makes them one of the most promising candidates for terawatt‐scale green energy production with low cost. However, the high boiling point solvents during the solution‐processed film deposition cause anisotropic crystal growth and toxic solvent vapor during high‐throughput manufacturing. Here, a dual‐component green solvent consisting of isopropyl acetate and acetonitrile is proposed to form a volatile perovskite precursor, which can realize the high‐quality perovskite thin film deposition by intermediate phase regulation. A room‐temperature stable perovskite intermediate phase is constructed with the engagement of isopropyl acetate as co‐solvent, which suppresses the exploding nucleation rate in volatile perovskite precursor, providing a fine grain growth rate and wide processing window in scalable film deposition. The corresponding PSCs fabricated by blade coating without anti‐solvents or gas quenching achieve power conversion efficiency (PCE) of 16.37 % and 15.29 % for the areas of 14.08 cm2 and 37.83 cm2, respectively. [ABSTRACT FROM AUTHOR]

The unprecedented development of perovskite solar cells (PSCs) makes them one of the most promising candidates for terawatt‐scale green energy production with low cost. However, the high boiling point solvents during the solution‐processed film deposition cause anisotropic crystal growth and toxic solvent vapor during high‐throughput manufacturing. Here, a dual‐component green solvent consisting of isopropyl acetate and acetonitrile is proposed to form a volatile perovskite precursor, which can realize the high‐quality perovskite thin film deposition by intermediate phase regulation. A room‐temperature stable perovskite intermediate phase is constructed with the engagement of isopropyl acetate as co‐solvent, which suppresses the exploding nucleation rate in volatile perovskite precursor, providing a fine grain growth rate and wide processing window in scalable film deposition. The corresponding PSCs fabricated by blade coating without anti‐solvents or gas quenching achieve power conversion efficiency (PCE) of 16.37 % and 15.29 % for the areas of 14.08 cm2 and 37.83 cm2, respectively. [ABSTRACT FROM AUTHOR]

Post‐treatment techniques of tunnel oxide passivated contact (TOPCon) structure are universally implemented via executing an additional hydrogenation process to optimize the passivation performance. However, the underlying physical mechanism and which method is most applicable are still being investigated. Herein, the effectiveness of thermal annealing in water vapor and N2 atmosphere is studied, which is both environmentally friendly and easy to operate. It is demonstrated that compared to other common hydrogenation techniques, the wet N2 outperforms in improving the passivation performance, which can be attributed to the neutralization of internal defects in poly‐Si and the optimization of structural densities, and interestingly, this gain effect is amplified when this contact is doped with oxygen impurity. A power conversion efficiency of 22.62% is achieved using this technology which verifies its reliability and applicability. A loss analysis based on numerical simulations, outlining ways to achieve higher conversion efficiency and highlighting the great potential of this technology is also provided. Extensive experiments and first‐principles calculations based on density‐functional theory are conducted to clarify the underlying dynamics, including the surface adsorption process and the potentiation mechanisms, revealing that passivation and neutralization of hydrogen atoms couple with the compactness optimization of the structure. [ABSTRACT FROM AUTHOR]

The detrimental effect of tail states on the radiative and non‐radiative voltage loss has been demonstrated to be a limiting factor for the open circuit voltage (VOC) in Cu(In,Ga)Se2 solar cells. A strategy that has proven effective in reducing tail states is the addition of alkali metals, the effect of which has been associated with the passivation of charged defects at grain boundaries. Herein, tail states in Cu(In,Ga)Se2 are revisited by studying the effect of compositional variations and alkali incorporation into single‐crystal films. The results demonstrate that sodium and potassium decrease the density of tail states despite the absence of grain boundaries, suggesting that there is more to alkalis than just grain boundary effects. Moreover, an increase in doping as a result of sodium or potassium incorporation is shown to contribute to the reduced tail states, which are demonstrated to arise largely from electrostatic potential fluctuations and to be determined by grain interior properties. By analyzing the voltage loss in high‐efficiency polycrystalline and single crystalline devices, this work presents a model that explains the entirety of the voltage loss in Cu(In,Ga)Se2 based on the combined effect of doping on tail states and VOC. [ABSTRACT FROM AUTHOR]

Nickel oxide (NiOx$\left(\text{NiO}\right)_{x}$) is a promising hole transport material for perovskite/Si tandem solar cells. Various silicon cell architectures may be used as bottom cells. The polycrystalline (poly‐Si) p+/n+$\left(\text{p}\right)^{+} / \left(\text{n}\right)^{+}$ tunnel diode is expected to be a high‐efficiency interconnection scheme between the two subcells of monolithic tandems in p‐i‐n configuration with a high thermal budget, excellent passivation properties, and low contact resistivity. However, NiOx$\left(\text{NiO}\right)_{x}$ is then interfaced to poly‐Si(p+$\left(\text{p}\right)^{+}$) and the chemical integrity of the interface due to the necessity of annealing treatments has to be questioned. For this purpose, the NiOx$\left(\text{NiO}\right)_{x}$/poly‐Si contact resistivity for different annealing temperatures is investigated between 100 and 500 °C, and two different NiOx$\left(\text{NiO}\right)_{x}$ deposition techniques, namely, wet‐chemically applied and sputter‐deposited NiOx$\left(\text{NiO}\right)_{x}$. The values of more than 1 Ω cm2$1 \textrm{ } \Omega \textrm{ } \left(\text{cm}\right)^{2}$ are obtained. The insertion of a nm‐thin metallic Ni interlayer is shown to enable a tremendous decrease of the contact resistivity by 2–3 orders of magnitude. The formation of NiSi2$\left(\text{NiSi}\right)_{2}$ is proven by highly resolved (scanning) transmission electron microscopy ((S)TEM) coupled with energy‐dispersive X‐ray spectroscopy (EDXS). This interfacial engineering approach is expected to provide an effective way of improving the contact properties and integrability of NiOx$\left(\text{NiO}\right)_{x}$ into various tandem cell processes. [ABSTRACT FROM AUTHOR]

The origins of parasitic heating for photovoltaic (PV) technologies based on silicon, perovskites, and their combination in monolithic tandems are investigated. To quantify heating losses, the cooling score (CS) as a new simple metric, representing the percentage of incident solar irradiance not contributing to module heating is introduced. This is a function of both the optical structure and power conversion efficiency (PCE) of the PV modules and allows a fair comparison between different technologies under identical performance‐evaluation scenarios. Silicon single‐junction devices have the lowest CS due to their low bandgap (causing significant carrier thermalization losses) and their use of light‐trapping structures to increase their PCE which also undesirably increases parasitic absorption of sub‐bandgap photons. Conversely, perovskite single‐junction devices show the highest CS in all studied performance‐evaluation scenarios thanks to their wider bandgap and high absorption coefficient, enabling absorption of all solar photons that may contribute to the photocurrent without requiring light‐trapping structures. While perovskite/silicon tandems minimize thermalization losses, they also usually employ light‐trapping structures in their bottom cell to increase their PCE, which lowers their CS. Through simulation and outdoor experiments, it is demonstrated that an efficient module‐cooling environment may significantly suppress the detrimental effects associated with a low CS. [ABSTRACT FROM AUTHOR]

Silicon (Si) is a low‐cost, stable photovoltaic market contributor which is approaching its single‐junction theoretical efficiency limit. To further elevate the efficiency of crystalline Si (c‐Si) afterward, Si solar cells (SCs) need a proper top cell absorber in Si tandem SCs. Herein, the top cell absorber is studied by evaluating their current state of the art, the existing challenges, and possible future solutions which can enhance their efficiency. The progress of perovskite/Si tandem SC both for monolithic and four terminals is exceptional but still many challenges limit their commercialization. In view of these challenges, the relative's solutions are prescribed in detail to make possible their realization. III–V semiconductors being mature candidates still face a growth/fabrication problem, which makes them a costly option for III–V/Si tandem SCs. Effective growth strategies along with technical solutions are discussed in detail. Emerging chalcogenides are considered the future of tandem technology. Recent developments in the chalcogenides/Si tandem SC are highlighted and the possible options are presented. In the end, a short note is given on the near future tandem materials for Si tandem SCs. [ABSTRACT FROM AUTHOR]

This study entails the examination of tunnel oxide passivated contact on p‐type silicon wafers (p‐TOPCon) passivated with n‐polysilicon for a solar cell by using Quokka‐3, a numerical simulation program. The effects of the thickness, bulk lifetime, resistivity, and selectivity of charge carriers due to the polysilicon passivated contact are investigated. Through such n‐polysilicon passivated contact, the back‐emitter solar cells engender higher internal power owing to enhanced surface passivation. This further reduces the shading loss due to front metallization; however, the reduced minority carrier lifetime of the p‐type Czochralski (Cz) wafer restricts the possibilities for high efficiency. Subsequently, the minority charge carrier lifetime of the p‐type wafer conceivably becomes an obstacle to realizing TOPCon solar cells with a high conversion efficiency. This study demonstrates that a configuration suitable for the industrial manufacturing of high‐efficiency solar cells is a crystalline silicon solar cell on a p‐type wafer through a rear‐emitter n‐polysilicon passivated contact. A roadmap toward 24.87% of the p‐TOPCon solar cells through the n‐type polysilicon passivated contact is also devised. [ABSTRACT FROM AUTHOR]