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Thermal evaporation can significantly facilitate scalable, uniform, and conformal perovskite film, particularly well‐suited for the preparation of perovskite/silicon (Si) tandem solar cells. However, the perovskite material easily induces a phase transition from a photoactive phase to a photoinactive phase, limiting the development of the stability and efficiency of tandem cells. Introducing lead chloride (PbCl2) into wide‐bandgap perovskite materials is beneficial for the fabrication of efficient and stable light‐absorbing materials, but the microscopic mechanism of the effect of PbCl2 on perovskite is still unclear. The study here reports evidences that the addition of PbCl2 to improve perovskite film stability and optoelectronic performance is due to the minor octahedral tilting of the perovskite structure are reported. It also demonstrates that this strategy accelerates interfacial charge transfer and carrier diffusion in the perovskite bulk and heterojunction interfaces. Therefore, the wide‐bandgap perovskite solar cells (PSCs) prepared by adding PbCl2 exhibit a champion power conversion efficiency (PCE) of 17.80%. The PSCs retain 97% of their performance following 200 h of operation at the maximum power point under full 1‐sun illumination. Finally, monolithic perovskite/Si tandem cells with record PCEs of 27.43% and an open‐circuit voltage of 1.817 V are fabricated. [ABSTRACT FROM AUTHOR]

Inorganic cesium lead halide perovskites offer a pathway towards thermally stable photovoltaics. However, moisture‐induced phase degradation restricts the application of hole transport layers (HTLs) with hygroscopic dopants. Dopant‐free HTLs fail to realize efficient photovoltaics due to severe electrical loss. Herein, we developed an electrical loss management strategy by manipulating poly(3‐hexylthiophene) with a small molecule, i.e., SMe‐TATPyr. The developed P3HT/SMe‐TATPyr HTL shows a three‐time increase of carrier mobility owing to breaking the long‐range ordering of "edge‐on" P3HT and inducing the formation of "face‐on" clusters, over 50 % decrease of the perovskite surface defect density, and a reduced voltage loss at the perovskite/HTL interface because of favorable energy level alignment. The CsPbI2Br perovskite solar cell demonstrates a record‐high efficiency of 16.93 % for dopant‐free HTL, and superior moisture and thermal stability by maintaining 96 % efficiency at low‐humidity condition (10–25 % R. H.) for 1500 hours and over 95 % efficiency after annealing at 85 °C for 1000 hours. [ABSTRACT FROM AUTHOR]

Inorganic cesium lead halide perovskites offer a pathway towards thermally stable photovoltaics. However, moisture‐induced phase degradation restricts the application of hole transport layers (HTLs) with hygroscopic dopants. Dopant‐free HTLs fail to realize efficient photovoltaics due to severe electrical loss. Herein, we developed an electrical loss management strategy by manipulating poly(3‐hexylthiophene) with a small molecule, i.e., SMe‐TATPyr. The developed P3HT/SMe‐TATPyr HTL shows a three‐time increase of carrier mobility owing to breaking the long‐range ordering of "edge‐on" P3HT and inducing the formation of "face‐on" clusters, over 50 % decrease of the perovskite surface defect density, and a reduced voltage loss at the perovskite/HTL interface because of favorable energy level alignment. The CsPbI2Br perovskite solar cell demonstrates a record‐high efficiency of 16.93 % for dopant‐free HTL, and superior moisture and thermal stability by maintaining 96 % efficiency at low‐humidity condition (10–25 % R. H.) for 1500 hours and over 95 % efficiency after annealing at 85 °C for 1000 hours. [ABSTRACT FROM AUTHOR]

At present, one of the major factors limiting the further improvement of inverted (p‐i‐n) perovskite solar cells (PSCs) is trap‐assisted non‐radiative recombination at the perovskite/electron transporting layer (ETL) interface. Surface passivation with organic ammonium salt is a powerful strategy to improve the performance of PSCs. Herein, an effective method by using propylamine hydroiodide (PAI) and 1,3‐diaminopropane dihydroiodide (PDADI) is reported to modify the perovskite/ETL interface. These two ammonium salts do not form new perovskite but directly passivate the defects on the perovskite surface after annealing. The results show that the PDADI‐modified perovskite films possess a lower surface defect density and less non‐radiative recombination as well as improved charge carrier transport. Based on this strategy, the PDADI‐modified p‐i‐n PSCs deliver an impressive efficiency of 25.09% (certified 24.58%) with an open‐circuit voltage of 1.184 V. Furthermore, the unencapsulated PDADI‐modified PSCs also exhibit good storage stability, retaining 91% of initial PCE at 65 °C in a N2 glove box for 1300 h. This strategy provides an efficient route to fabricate highly efficient and stable inverted p‐i‐n structured PSCs. [ABSTRACT FROM AUTHOR]

A new small molecular hole-transporting material, 1,3,6,8-tetrakis[N-(p-methoxyphenyl)-N′-(9,9′-dimethyl-9H-fluoren-2-yl)-amino]pyrene (TFAP) was synthesized and applied in CH3NH3PbI3-perovskite solar cells. A best power conversion efficiency of 19.7% with a photovoltage of 1.11 V has been achieved. [ABSTRACT FROM AUTHOR]

Abstract: A readily available small molecular hole‐transporting material (HTM), OMe‐TATPyr, was synthesized and tested in perovskite solar cells (PSCs). OMe‐TATPyr is a two‐dimensional π‐conjugated molecule with a pyrene core and four phenyl‐thiophene bridged triarylamine groups. It can be readily synthesized in gram scale with a low lab cost of around US$ 50 g−1. The incorporation of the phenyl‐thiophene units in OMe‐TATPyr are beneficial for not only carrier transportation through improved charge delocalization and intermolecular stacking, but also potential trap passivation via Pb–S interaction as supported by depth‐profiling XPS, photoluminescence, and electrochemical impedance analysis. As a result, an impressive best power conversion efficiency (PCE) of up to 20.6 % and an average PCE of 20.0 % with good stability has been achieved for mixed‐cation PSCs with OMe‐TATPyr with an area of 0.09 cm2. A device with an area of 1.08 cm2 based on OMe‐TATPyr demonstrates a PCE of 17.3 %. [ABSTRACT FROM AUTHOR]

Abstract: A readily available small molecular hole‐transporting material (HTM), OMe‐TATPyr, was synthesized and tested in perovskite solar cells (PSCs). OMe‐TATPyr is a two‐dimensional π‐conjugated molecule with a pyrene core and four phenyl‐thiophene bridged triarylamine groups. It can be readily synthesized in gram scale with a low lab cost of around US$ 50 g−1. The incorporation of the phenyl‐thiophene units in OMe‐TATPyr are beneficial for not only carrier transportation through improved charge delocalization and intermolecular stacking, but also potential trap passivation via Pb–S interaction as supported by depth‐profiling XPS, photoluminescence, and electrochemical impedance analysis. As a result, an impressive best power conversion efficiency (PCE) of up to 20.6 % and an average PCE of 20.0 % with good stability has been achieved for mixed‐cation PSCs with OMe‐TATPyr with an area of 0.09 cm2. A device with an area of 1.08 cm2 based on OMe‐TATPyr demonstrates a PCE of 17.3 %. [ABSTRACT FROM AUTHOR]

Two new hole transporting materials (HTMs) based on triphenylamine and carbazole core moieties are designed and applied in planar perovskite solar cells. 18.2% power conversion efficiency (PCE) has been achieved, and 84% of the initial performance can be retained after 50 days. [ABSTRACT FROM AUTHOR]

Metal‐halide perovskite solar cells (PSCs) exhibit outstanding power conversion efficiencies (PCEs) when fabricated as mm‐sized devices, but creation of high‐performing large‐area modules that are stable on a sufficiently long timescale still presents a significant challenge. Herein, the quality of large‐area perovskite film is improved by using ionic liquid additives via forming a new Pb‐N bonding between the ionic liquid and Pb2+. This new bond can be modulated by a critical screening of the anion structure of the ionic liquid. The selected ionic liquid effectively reduces the defects of the perovskite films and markedly elongate their carrier lifetimes. As a result, a champion PCE of 24.4% for small‐area (0.148 cm2) devices and 20.4% for larger‐area (10.0 cm2) modules under AM 1.5G irradiation is achieved. More importantly, the modified devices retain 90% of their peak PCE after aging for 1900 h at 65 ± 5 °C (ISOS‐T‐1) and 80% after continuous light soaking for 750 h. The non‐encapsulated modules maintained 80% of their peak PCE after 1100 h of aging in the air with a relative humidity of 35 ± 5% and temperature of 25 ± 5 °C under dark (ISOS‐D‐1), showing great potential for future commercialization. [ABSTRACT FROM AUTHOR]

Semiconductor quantum dots (QDs) are nanocrystals whose excitons are bound in 3D space. Owning to their remarkable quantum confinement effect, QDs exhibit a discontinuous electronic energy level structure similar to that of atoms, leading to novel physical, optical, and electrical properties for various optoelectronic device applications including solar cells. Near‐infrared photoactive narrow bandgap (NBG) QDs can maximize the use of solar energy through the quantum size effect, offering a good opportunity for designing highly efficient wide‐spectrum responsive solar cells. This review analyzes the recent research progress of NBG QDs as light absorbing materials in solar cells. The critical elaboration of the latest achievements both in material design and device optimization for NBG QD‐based solar cells (QDSCs), including QD synthesis and film fabrication, design of device configuration, classification of NBG QDs and their photovoltaic performance, strategies for performance improvements is focused upon. The current challenges and perspectives for the further advance of NBG QDSCs are also discussed. [ABSTRACT FROM AUTHOR]

The optical absorption is the most important macroscopic process to characterize the microscopic optical transition in the semiconductor materials. Recently, great enhancement has been observed in the absorption of the active region within a p–n junction. In this paper, GaAs based p–i–n samples with the active region varied from 100 nm to 3 μm were fabricated and it was observed that the external quantum efficiencies are higher than the typical results, indicating a new mechanism beyond the established theories. We proposed a theoretical model about the abnormal optical absorption process in the active region within a strong electric field, which might provide new theories for the design of the solar cells, photodetectors, and other photoelectric devices. [ABSTRACT FROM AUTHOR]

Highlights • The TFSC is on a metallic thin film instead of the GaAs parent substrate. • Electroplating is employed to prepare the metal carrier instead of bonding generally used. • The substrate transferred process based on electroplating imposes little strain on the epilayers. • The TFSCs show a high efficiency, light weight, super thin style, flexibility and performance uniformity. • The flexibility is investigated by bending the TFSCs into different strain and with various bending recycles. Abstract We have investigated the characteristics of InGaP/GaAs double junction thin film solar cells (TFSCs) on a flexible metallic substrate prepared by electroplating copper (Cu). Both photoluminescence peaks of InGaP and GaAs sub-cells maintained the original positions after transferring the epilayers onto Cu carrier, but a peak shift occurred when the epilayers were bent under intense strain. A slight efficiency improvement up to 29.09% was obtained, compared with 28.25% of conventional structure with GaAs grown substrate under air mass 1.5 (AM1.5) illumination. The TFSCs have a total thickness of about 30 μm, showing an excellent flexibility. Performance measurements of TFSCs were conducted under different strain by bent into the corresponding central angles. It was found that the efficiency was keeping more than 90% when the strain was less than 0.1%, although a rapid decrease down to below 45% occurred till the strain was increased to 0.2%. The favorable performance maintaining after up to 100 bending recycles proved the superior mechanical stability of the TFSCs. Our presented transferring substrate technology based on electroplating in this paper enables the TFSCs with an outstanding performance uniformity, a high yield and a large power weight ratio, which will exhibit an enormous potential to fabricate flexible, low-weight, thin film optoelectronic devices. [ABSTRACT FROM AUTHOR]

PbS colloidal quantum dots (QDs) have emerged as one of the most promising photovoltaic solar cells material. The synthesis of PbS QDs generally uses TMS 2 S as sulfur source. However, the volatile and environmentally unfriendly properties of TMS 2 S will limit its industrial applications. This paper presents a new method of synthesizing PbS QDs employing a CdS QDs/ODE solution as the sulfur precursor by exploiting a cation exchange reaction. The resulting QDs show a performance comparable with previous work for solar cells. Through optimizing the architecture of the photoactive layer, excellent stability in air is achieved. An efficiency of 7.89% is retained in air after 110 days. [ABSTRACT FROM AUTHOR]

Colloidal quantum-dot (QD) solar cells have emerged as one of the most promising photovoltaic techniques. Herein, we report an inverted PbS QD solar cells employing solution-processed CdS as the electron acceptor materials. Chemical bath deposition – one featuring ease of fabrication and compatibility with a low-temperature process – was employed to prepare CdS film on FTO glass, followed by deposition of PbS QDs as absorbing layer in a layer-by-layer fashion, thereby forming a depleted heterojunction structure. The results suggested that the thickness of CdS layer can be a key factor for determining the photovoltaic performance. After systematical optimization, an inverted FTO/CdS/PbS QDs/MoO 3 /Ag structure with an ultra-thin CdS film of 40 nm delivered a decent power conversion efficiency of 5.22%. The maximum temperature is ~85 °C via device fabrication demonstrates potential large-scale production process. [ABSTRACT FROM AUTHOR]

A novel multi-functional interface material (TAAPyr) is first developed as a defect passivation layer and a protect layer against moisture for PSCs application. Consequently, the efficiency of TAAPyr-based device can increase form 20.37% to 22.45%, with an unencapsulated device retaining 90% of its initial efficiency after storage for 600h at ∼65% humidity. [Display omitted] • A hydrophobic multi-functional interface material is developed for PSCs application. • TAAPyr-treated PSCs shows an improvement in efficiency from 20.37% to 22.45%. • Device long-term stability has greatly been enhanced. Surface treatment of perovskite films with interface materials is an effective strategy to resolve trap-mediated nonradiative recombination toward high efficiency and stability of perovskite solar cells (PSCs). However, interface materials for multi-functional treatment have been rarely investigated in PSCs. In this work, a novel pyrene-based organic material (TAAPyr) is first introduced as a defect passivation layer and a protect layer against moisture for PSCs application. With the TAAPyr interfacial modification, both perovskite surface defects and nonradiative recombination are effectively decreased as well as the carrier transport in device is also enhanced, As a consequence, the best power conversion efficiencies (PCE) up to 22.45% for TAAPyr-based device was obtained, clearly outperforming the control one (20.37%). Moreover, it was found that the π-conjugated TAAPyr can promote intermolecular face-to-face stacking on the surface perovskite film, which is favorable to making the perovskite surface more hydrophobic and consequently enhance PSCs long-term stability. The un-encapsulated PSCs can retain 92% of the initial PCE after storage for 600 h at ∼65% RH, in comparison with 64% efficiency retention of the device without TAAPyr under the same conditions. This work presents a new strategy to enhance the efficiency and stability of PSCs by multi-functional π–conjugated passivator. [ABSTRACT FROM AUTHOR]