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The commonly-used superstrate configuration (depositing front subcell first and then depositing back subcell) in all-perovskite tandem solar cells is disadvantageous for long-term stability due to oxidizable narrow-bandgap perovskite assembled last and easily exposable to air. Here we reverse the processing order and demonstrate all-perovskite tandems in a substrate configuration (depositing back subcell first and then depositing front subcell) to bury oxidizable narrow-bandgap perovskite deep in the device stack. By using guanidinium tetrafluoroborate additive in wide-bandgap perovskite subcell, we achieve an efficiency of 25.3% for the substrate-configured all-perovskite tandem cells. The unencapsulated devices exhibit no performance degradation after storage in dry air for 1000 hours. The substrate configuration also widens the choice of flexible substrates: we achieve 24.1% and 20.3% efficient flexible all-perovskite tandem solar cells on copper-coated polyethylene naphthalene and copper metal foil, respectively. Substrate configuration offers a promising route to unleash the commercial potential of all-perovskite tandem solar cells. The superstate configuration in all-perovskite tandem solar cells is disadvantageous for long-term stability. Here, the authors reverse the processing order and demonstrate substrate configuration to bury oxidizable narrow-bandgap perovskites, and achieve efficiency of 25.3% with long stability. [ABSTRACT FROM AUTHOR]

The wide‐bandgap perovskite solar cell is a crucial part of perovskite/silicon tandem solar cells, which offer an avenue for surpassing the power conversion efficiency (PCE) limit of single‐junction silicon solar cells. However, the actual efficiency of such tandem solar cells today is diminished by the nonradiative recombination losses in the wide‐bandgap perovskite subcells. Here, this work reports a grain regrowth and bifacial passivation (GRBP) strategy to reduce recombination losses at the grain boundaries and perovskite/charge transport layer interfaces simultaneously. This is achieved by a posttreatment of perovskite films with a mixture of methylammonium thiocyanate (MASCN) and phenethylammonium iodide (PEAI). The MASCN induces the regrowth of perovskite grains and simultaneously facilitates the penetration of PEAI into the hole‐transport‐layer (HTL)/perovskite bottom interface. Thereby, the bulk and interface nonradiative recombination losses are reduced and the open‐circuit voltage in solar cells is considerably increased. PCEs of 21.9% and 19.9% for the 1.65‐eV bandgap opaque and semitransparent perovskite solar cells, respectively, are obtained. The encapsulated semitransparent perovskite solar cells retain their initial efficiency following 500 h of operation under one‐sun illumination in ambient conditions. The perovskite/silicon 4‐terminal (4‐T) tandem cells are fabricated with impressive PCEs 29.8% and 28.5% for 0.049 cm2 and 1 cm2 devices, respectively. [ABSTRACT FROM AUTHOR]

Commercialization of all‐perovskite tandem solar cells requires thermally stable narrow‐bandgap (NBG) perovskites and tunnel junction. However, the high content of methylammonium (MA) and organic hole transport layer used in NBG perovskite subcell undermine the thermal stability of all‐perovskite tandems. Here, thermally stable mixed lead‐tin NBG perovskite solar cells (PSCs) are developed by using only formamidinium (FA) for the A‐site cation. Solution‐processed indium tin oxide nanocrystals (ITO NCs) are deployed further to replace the conventional organic charge transport layer. Meanwhile, the ITO NCs layer simultaneously functions as a recombination layer in the tunnel junction, which simplifies the architecture of all‐perovskite tandem devices. The thermally stable all‐FA Pb‐Sn PSCs achieve a high power conversion efficiency (PCE) of 21.0%. With the thermally stable all‐FA NBG perovskite and optimized tunnel junction, a stabilized PCE of 26.3% is further obtained in all‐perovskite tandems. The unencapsulated tandem devices maintain >90% of their initial efficiencies after 212 h aging at 85 °C in the N2 atmosphere. The strategies herein offer a crucial step toward efficient and thermally stable all‐perovskite tandem solar cells. [ABSTRACT FROM AUTHOR]

Efficient inverted (pâ€"iâ€"n) type CsPbI3 perovskite solar cells (PSCs) have revealed promising applications due to their excellent thermal and photostability. Regulating the nucleation and crystallization of perovskite film is an important route to improving the performance of CsPbI3 PSCs. Herein, we explored cesium acetate (CsAc) as additive to manipulate the crystallization process of CsPbI3 perovskite films. By involving in the intermediate phase DMA1- x Cs x PbI3- y Ac y of perovskite, the pseudo-halide acetate (Acâˆ') can retard the ion exchange reaction between DMA+ and Cs+, leading to a perovskite with dense morphology, low defect density, and a long carrier lifetime. As a result, the optimal CsPbI3 PSCs yielded a high power conversion efficiency of 18.3%. Moreover, the encapsulated devices showed excellent operational stability and the devices retained their initial performance following 500 h of operation at the maximum power point under one-sun illumination in ambient conditions. [ABSTRACT FROM AUTHOR]

All‐perovskite tandem solar cells offer a promising avenue to go beyond the efficiency limit of single‐junction devices. Their efficiencies have been increasing rapidly in the past few years; however, their commercial viability is hindered by the instability under thermal stressing. Herein, comprehensive device design strategies are proposed to achieve thermally stable all‐perovskite tandem solar cells while retaining the advantages of solution processing. Metal oxides, i.e., NiOx and SnO2, are used for the hole and electron transport layers in both wide bandgap and narrow subcells. The metal‐based recombination layer is replaced with a stable and conductive indium tin oxide nanocrystals film to fabricate an all metal‐oxide‐based tunnel junction. Based on those design strategies, the encapsulated all‐perovskite tandem solar cells retained 85% of their initial efficiency after stressing at 85 °C for 2500 h and maintained >80% of their initial performance after 900 h operation at the maximum power point and operating temperature of ≈65 °C. Achieving such thermal stability represents a crucial step toward commercial viability of all‐perovskite tandem solar cells. [ABSTRACT FROM AUTHOR]

Currently, most two‐dimensional (2D) metal halide perovskites are of the Ruddlesden–Popper type and contain the thermally unstable methylammonium (MA) molecules, which leads to inferior photovoltaic performance and mild stability. Here we report a new type of MA‐free formamidinium (FA) based low‐dimensional perovskites, featuring a general formula of (PDA)(FA)n−1PbnI3n+1 with propane‐1,3‐diammonium (PDA) as the organic spacer cation. The perovskite films with well‐oriented crystal grains are attained under the assistance of the FACl additive, where the role of Cl is investigated through the grazing‐incidence X‐ray diffraction technique. The photovoltaic device based on the optimized (PDA)(FA)3Pb4I13 film demonstrates a remarkable power conversion efficiency of 13.8 %, the highest record for the FA‐based 2D perovskite solar cells. In addition, compared to (PDA)(MA)3Pb4I13, the MA‐containing analogue and a renowned stable 2D perovskite, both the (PDA)(FA)3Pb4I13 films and their derived devices exhibit exceedingly higher thermal stability. [ABSTRACT FROM AUTHOR]

ZnO nanorod films prepared using different electrochemical deposition processes have been employed as photoelectrodes for Sb2S3 quantum-dot-sensitized solar cells. The density and diameter of the ZnO nanorods were adjusted by varying the electrochemical deposition time. The optical absorption and photoluminescence spectra of the different Sb2S3-sensitized ZnO nanorod photoelectrodes were investigated, revealing that the best optical absorption and charge separation properties were exhibited by the Sb2S3-sensitized ZnO nanorod photoelectrodes obtained using an electrochemical deposition time of 120 min. The charge transfer property of the quantum-dot-sensitized solar cells was also optimized by using ZnO nanorods with different structures. The Sb2S3-based quantum-dot-sensitized solar cells based on the ZnO nanorod photoelectrodes with relatively high density and low diameter fabricated using a deposition time of 120 min exhibited excellent charge generation and transfer properties, enabling higher current density and thereby a photovoltaic power conversion efficiency of 2.04%. [ABSTRACT FROM AUTHOR]

The methylammonium (MA)‐free perovskite solar cells (PSCs) have drawn broad attention due to their excellent thermostability. However, the efficiency of these devices is inferior to most state‐of‐the‐art PSCs. Herein, the photovoltaic performance of the MA‐free PSCs is enhanced by constructing interfacial capping layers with a pair of alkylammonium halides, n‐propylammonium (PA) iodide and propane‐1,3‐diammonium (PDA) iodide. The structure and composition of the interfacial layers are comprehensively investigated and their correlation with the device performance is presented in terms of defect passivation efficacy, energy level alignment, and hydrophobicity for moisture resistance. The PSC devices based on the PAI and PDAI2 treated MA‐free perovskite films demonstrate better power conversion efficiencies (PCEs) and stabilities than the reference devices without the interfacial layers. Although the PAI‐treated devices exhibit the highest PCE of 21.1%, the PDAI2‐treated PSCs demonstrate the exceptional thermal and humidity stabilities. [ABSTRACT FROM AUTHOR]

Interfacial engineering is crucial for perovskite solar cells (PSCs) to ensure efficient charge carrier transfer, and pivotal for device performances. Herein, a novel cross‐linked PCBM (CL‐PCBM) interlayer at the perovskite/electron transport layer (ETL) interface of the methylammonium‐free PSC device is incorporated. The dimeric PCBM interlayer prepared using a facile UV cross‐linking technique concurrently improves the quality of the resultant perovskite film and the charge transfer capability of the ETL, leading to significantly enhanced device photovoltaic performances. In addition, the PSC devices integrating the CL‐PCBM interlayers exhibit superior humidity and UV stabilities. The successful employment of the CL‐PCBM interlayer can bring new insight into the design and engineering of high‐quality interfaces for efficient PSCs. [ABSTRACT FROM AUTHOR]

We have designed a universal absorber structure for materials with high loss ability but mismatched impedance. The absorption performance can be significantly improved by inserting a lossless layer, such as air, between the metal backing and the absorption layer. The inserted layer works as the phase-tuning layer, improving the impedance-matching condition and enhancing the absorption layer's loss. By applying the structure to three different materials (Graphene, Ce 0.75 Sm 1.25 Fe 17 N 3-δ , and Mn), we prove the effectiveness of this structure. Notably, in the case of Ce 0.75 Sm 1.25 Fe 17 N 3-δ , we can get an absorber with an absorption layer as thin as a sheet of A4 paper (only 0.1 mm), with an effective absorption bandwidth (EAB) of 8.5 GHz and a strongest absorption peak of − 44 dB. This means a surface density of 0.031 g/cm2 can be achieved theoretically, much lighter than many reported absorbers constructed from metal composites, which is particularly beneficial for mass-sensitive applications. In addition, for the practical feasibility of preparation, the phase-tuning layer can also be composed of other lossless mediums such as paraffin, Teflon, and aerosol, which can achieve a similar effect to air. ● A universal double-layer structure has been designed to improve the performance of materials with high loss ability but mismatched impedance by inserting a lossless layer (such as air, paraffin, Teflon and aerosol) to tune the phase of microwaves. ● The effectiveness of this structure is demostrated on three different types of materials and their bandwidths are significantly improved with this structural modification (Graphene: 5.7 GHz → 7.4 GHz, Ce 0.75 Sm 1.25 Fe 17 N 3-δ : 0 → 8.5 GHz, Mn: 0 → 6.9 GHz). ● For Ce 0.75 Sm 1.25 Fe 17 N 3-δ , we can get an absorber with an absorbing layer as thin as a sheet of A4 paper (only 0.1 mm), with an EAB of 8.5 GHz and the strongest absorption peak of − 44 dB. [ABSTRACT FROM AUTHOR]

SnO 2 has attracted extensive attention in planar perovskite solar cells (PSCs) owing to its outstanding photoelectric properties and low temperature preparation. However, pinholes are easy to appear in the annealing process of SnO 2 films, which limits its application in planar PSCs. Here lists a simple and low-cost method: Urea-complexed tin oxide in deionized water can effectively control the concentration of SnO 2. This process is conducive to forming a compact surface morphology. Meanwhile, the work explored the effect of the properties of PSCs with different thicknesses of SnO 2 layers. The system analysis showed that PSCs based on 60 nm SnO 2 layer and the methamphetamine lead iodide (MAPbI 3) light absorber yielded the highest power conversion efficiency (PCE) over 18%, a fill factor (FF) of 0.793, and good stability. Therefore, we believe our study provides an effective way for preparing electron transport layers. [ABSTRACT FROM AUTHOR]

Sb2S3 quantum dot is prepared as the optical absorber on the ZnO nanorod films to fabricate high-efficiency quantum dot–sensitized solar cells. The band energy of the solar cells is modulated by the different concentration of Cu-doping. Meanwhile, the optical absorption spectra and photoluminescence spectra of different ZnO/Sb2S3 photoelectrodes are investigated, which had exhibited the enhancement on optical absorption property and charge separation property by Cu-doping process. The charge transfer properties of the solar cells had also been enhanced by the modulation on band energy structure by different Cu-doping concentration. With the relatively larger optical absorption edge, the 0.3 mM Cu–doped ZnO/Sb2S3 quantum dot–sensitized solar cells have exhibited optimal band energy structure for charge transfer, which can obtain higher current density to enhance the photovoltaic power conversion efficiency from 2.55 to 3.14%. [ABSTRACT FROM AUTHOR]

2D perovskites hold a great prospective to create highly efficient and stable solar cell devices. In order to explore their full potential, every component of 2D perovskite solar cells (PSCs) has to be carefully designed and engineered. Herein, the metal ion doping strategy is taken to optimize both the hole transport layers (HTLs) and the light absorbing layers of the BA2MA3Pb4I13 (BA = butylamine; MA = methylammonium) based 2D PSC devices. The hole extraction and transport abilities are significantly enhanced by Cu ion doping in the nickel oxide layers, while the optoelectronic properties of the BA2MA3Pb4I13 layers are effectively improved with Cs ion doping. The synergistic incorporations of Cu and Cs ions have boosted the device power conversion efficiency to 13.92%, the highest for 2D PSCs based on inorganic HTLs. In addition, the inorganic nature of the Cu doped nickel oxide film and the high quality of the Cs doped 2D perovskite film also endow the PSC device with extraordinary humidity and thermal stabilities. [ABSTRACT FROM AUTHOR]

Highlights from the article: Photovoltaic Devices: In Situ Observation of Crystallization Dynamics and Grain Orientation in Sequential Deposition of Metal Halide Perovskites (Adv. Funct. In article number 1902319, featuring a synchrotron-based in situ X-ray diffraction technique, Gang Chen and co-workers investigate the sequential deposition process of FAPbI SB 3 sb from a smooth PbI SB 2 sb film to a trilayer PbI SB 2 sb -FAI composite film and finally to the oriented perovskite film. The effects of the additive ions of Br SP - sp , Cl SP - sp , and MA SP + sp on the crystallization dynamics and grain orientation of the resultant perovskite films are also surveyed.

Metal halide perovskites have revolutionized the development of highly efficient, solution‐processable solar cells. Further advancements rely on improving perovskite film qualities through a better understanding of the underlying growth mechanism. Here, a systematic in situ grazing‐incidence X‐ray diffraction investigation is performed, facilitated by other techniques, on the sequential deposition of formamidinium lead iodide (FAPbI3)‐based perovskite films. The active chemical reaction, composition distribution, phase transition, and crystal grain orientation are all visualized following the entire perovskite formation process. Furthermore, the influences of additive ions on the crystallization speed, grain orientation, and morphology of FAPbI3‐based films, along with their photovoltaic performances, are fully evaluated and optimized, which leads to highly reproducible and efficient perovskite solar cells. The findings provide key insights into the perovskite growth mechanism and suggest the fabrication of high‐quality perovskite films for widespread optoelectronic applications. [ABSTRACT FROM AUTHOR]

ZnO nanorod films are prepared by electrochemical deposition process, which are employed as the photo-electrodes for the Sb 2 S 3 quantum dot sensitized solar cells. The orientation of ZnO nanorods (NRs) is modulated by different heating time. The changing on orientation of ZnO NRs has no influences on UV–Vis absorption spectra. And the photoluminescence spectra indicates that the random orientation ZnO NRs has the better charge separation property. Due to the much more transfer paths from the random orientation of ZnO NRs, the Sb 2 S 3 quantum dot sensitized ZnO NRs solar cells by heating time of 20 min has exhibited an excellent charge transfer property, which can obtain much higher current density of the solar cells, achieving a photovoltaic power conversion efficiency of 2.43%. • Different orientation of ZnO NRs are prepared for Sb 2 S 3 based photo-electrodes. • Excellent charge separation property have been exhibited for random orientation of ZnO NRs. • More paths and high rate of charge transfer property can be obtained by random orientation of ZnO NRs. • The random orientation of ZnO NRs/Sb 2 S 3 based solar cells exhibits photovoltaic efficiency of 2.43%. [ABSTRACT FROM AUTHOR]