Yingzhi Jin

Wavelength-selective properties are required for semitransparent photovoltaics with new applications such as power-generating windows for buildings and automobiles. Herein, a high-throughput optical design strategy for high-performance semitransparent organic solar cells (STOSCs) is demonstrated. Guided by simulations for over tens of millions of device configurations, a photonic-crystal-enhanced STOSC with nearly 11% power conversion efficiency and 30% visible light transmittance was achieved. The high-throughput optical method has wide potential applications, especially as related to designs including multi-objective and multi-layer thickness optimizations.

A simple yet effective side chain modulation on the backbone for obtaining both enhanced V _oc and J _sc simultaneously is demonstrated in this work. Compared with the controlled molecule 3TT‐CIC, 3TT‐OCIC showed PCE of 13.13% with improved V _oc of 0.69 V and J _sc of 27.58 mA cm⁻², and the tandem device gives an excellent efficiency of 15.72%.

Abstract

It is a great challenge to simultaneously improve the two tangled parameters, open circuit voltage (V _oc) and short circuit current density (J _sc) for organic solar cells (OSCs). Herein, such a challenge is addressed by a synergistic approach using fine‐tuning molecular backbone and morphology control simultaneously by a simple yet effective side chain modulation on the backbone of an acceptor–donor–acceptor (A–D–A)‐type acceptor. With this, two terthieno[3,2‐b]thiophene (3TT) based A–D–A‐type acceptors, 3TT‐OCIC with backbone modulation and 3TT‐CIC without such modification, are designed and synthesized. Compared with the controlled molecule 3TT‐CIC, 3TT‐OCIC shows power conversion efficiency (PCE) of 13.13% with improved V _oc of 0.69 V and J _sc of 27.58 mA cm⁻², corresponding to PCE of 12.15% with V _oc of 0.65 V and J _sc of 27.04 mA cm⁻² for 3TT‐CIC–based device. Furthermore, with effective near infrared absorption, 3TT‐OCIC is used as the rear subcell acceptor in a tandem device and gave an excellent PCE of 15.72%.

An energetic cascade between mixed and pure regions assists in suppressing recombination losses in nonfullerene acceptor (NFA)‐based organic solar cells. The impact of polymer–NFA blend composition upon film morphology, energetics, charge carrier recombination kinetics, and photocurrent properties is studied.

Abstract

Here, it is investigated whether an energetic cascade between mixed and pure regions assists in suppressing recombination losses in non‐fullerene acceptor (NFA)‐based organic solar cells. The impact of polymer‐NFA blend composition upon morphology, energetics, charge carrier recombination kinetics, and photocurrent properties are studied. By changing film composition, morphological structures are varied from consisting of highly intermixed polymer‐NFA phases to consisting of both intermixed and pure phase. Cyclic voltammetry is employed to investigate the impact of blend morphology upon NFA lowest unoccupied molecular orbital (LUMO) level energetics. Transient absorption spectroscopy reveals the importance of an energetic cascade between mixed and pure phases in the electron–hole dynamics in order to well separate spatially localized electron–hole pairs. Raman spectroscopy is used to investigate the origin of energetic shift of NFA LUMO levels. It appears that the increase in NFA electron affinity in pure phases relative to mixed phases is correlated with a transition from a relatively planar backbone structure of NFA in pure, aggregated phases, to a more twisted structure in molecularly mixed phases. The studies focus on addressing whether aggregation‐dependent acceptor LUMO level energetics are a general design requirement for both fullerene and NFAs, and quantifying the magnitude, origin, and impact of such energetic shifts upon device performance.

In article number 1900618, Changyong Cao, Jeffrey T. Glass and co‐workers invent a highly stretchable all‐solid‐state supercapacitor via crumpled CNT‐forest electrodes fabricated by harnessing the mechanical instability of a bilayer structure. The lower image shows the structure of the supercapacitor and the blanket‐like pattern of the crumpled CNT‐forest electrodes while the upper image demonstrates its potential applications in wearable electronics and beyond.

A portable and efficient solar‐rechargeable battery is designed by integrating/matching a perovskite solar module and aluminum‐ion battery on the bifunctional aluminum layer, which delivers high power density (above 5000 W kg⁻¹), high energy density, a record overall photoelectric conversion and storage efficiency of 12.04%, and robust cycling performance (only 0.18% reduction per cycle).

Abstract

The solar‐rechargeable electric energy storage systems (SEESSs), which can simultaneously harvest and store solar energy, are considered a promising next‐generation renewable energy supply system. However, the difficulty in meeting the demands of higher overall photoelectric conversion and storage efficiency (PCSE) with both high power density and large energy density in the current SEESSs severely limit their practical application. Herein, a new class is demonstrated of portable and highly efficient SEESS that uniquely integrates a perovskite solar module (PSM) and an aluminum‐ion battery (AIB) directly on a bifunctional aluminum electrode without any external circuit. Such nanostructural design in the SEESS not only exhibits fast photo‐charge/discharge rate (less than one minute) with high power density (above 5000 W kg⁻¹), but also delivers a high energy density (above 43 Wh kg⁻¹). By rationally matching the maximum power point voltage of PSM with AIB charging voltage, an excellent solar‐charging efficiency of 15.2% and a high PCSE of 12.04% are achieved, which is among the best in all reported portable SEESSs. Moreover, enhanced PCSE is observed as the light intensity decreases, which makes such SEESS immune from the geographical location and climate limitations for diverse practical applications.

Single‐walled carbon nanotube electrodes in organic solar cells and perovskite solar cells are reviewed from a synthesis and applications point of views. The emerging thin‐film solar cells have the potential to become next‐generation flexible and portable energy devices. Replacement of conventional electrodes by single‐walled carbon nanotubes is crucial in achieving such devices.

Abstract

Emerging solar cells, namely, organic solar cells and perovskite solar cells, are the thin‐film photovoltaics that have light to electricity conversion efficiencies close to that of silicon solar cells while possessing advantages in having additional functionalities, facile‐processability, and low fabrication cost. To maximize these advantages, the electrode components must be replaced by materials that are more flexible and cost‐effective. Researchers around the globe have been looking for the new electrodes that meet these requirements. Among many candidates, single‐walled carbon nanotubes have demonstrated their feasibility as the new alternative to conventional electrodes, such as indium tin oxide and metals. This review discusses various growth methods of single‐walled carbon nanotubes and their electrode applications in thin‐film photovoltaics.

In article number https://doi.org/10.1002/aenm.2018039761803976, Han Young Woo, Xugang Guo, and co‐workers incorporate a series of polycyclic aromatic hydrocarbons with distinct π‐conjugated cores, from naphthalene, anthracene, pyrene, to perylene into nonfullerene acceptors via simple and low‐cost synthetic routes. The optoelectronic properties of these acceptors can be tuned over a wide range, enabling a promising power conversion efficiency of 10.37% in additive‐free organic solar cells.

The side chain length of polymer donors can lead to miscibility differences. Shortening the side chains of polymer donors improves the device performance of fullerene‐based solar cells, but deteriorates the performance of small molecular and polymeric nonfullerene solar cells. Morphology investigations unveil that the miscibility between donor and acceptor in blend films depends on the side chain length of polymer donors.

Abstract

The development of nonfullerene acceptors has brought polymer solar cells into a new era. Maximizing the performance of nonfullerene solar cells needs appropriate polymer donors that match with the acceptors in both electrical and morphological properties. So far, the design rationales for polymer donors are mainly borrowed from fullerene‐based solar cells, which are not necessarily applicable to nonfullerene solar cells. In this work, the influence of side chain length of polymer donors based on a set of random terpolymers PTAZ‐TPD10‐Cn on the device performance of polymer solar cells is investigated with three different acceptor materials, i.e., a fullerene acceptor [70]PCBM, a polymer acceptor N2200, and a fused‐ring molecular acceptor ITIC. Shortening the side chains of polymer donors improves the device performance of [70]PCBM‐based devices, but deteriorates the N2200‐ and ITIC‐based devices. Morphology studies unveil that the miscibility between donor and acceptor in blend films depends on the side chain length of polymer donors. Upon shortening the side chains of the polymer donors, the miscibility between the donor and acceptor increases for the [70]PCBM‐based blends, but decreases for the N2200‐ and ITIC‐based blends. These findings provide new guidelines for the development of polymer donors to match with emerging nonfullerene acceptors.

For the first time a novel type of solar device based on the heterojunction formed by 2D MXene and silicon with an initial power conversion efficiency of above 10% is introduced. This work potentially provides a new possibility to overcome the worldwide fuel shortage in the near future.

Abstract

A novel type of solar cell has been developed based on charge separation at the heterojunction formed by a transparent conducting MXene electrode and an n‐type silicon (n‐Si) wafer. A thin layer of the native silicon dioxide plays an important role in suppressing the recombination of charge carriers. A two‐step chemical treatment can increase the device efficiency by about 40%. Promisingly, an average power conversion efficiency of over 10% under simulated full sunlight is achieved for this novel class of solar cell with the application of an antireflection layer. The efficiencies of these novel solar cells based on a MXene‐Si heterojunction achieved in this work point to great promise in emerging photovoltaic technology. In addition to their high efficiency, the excellent reproducibility of such devices establishes a solid base for possible future commercialization.

A flexible asymmetric supercapacitor device is fabricated by using CC@NiCo₂Al‐LDH with mixed morphologies of 1D nanowires and 2D nanosheets as the positive electrode. ZIF‐8 derived porous carbon (ZPC), PVA/KOH, and filter paper serve as the negative electrode, solid‐state electrolyte, and seperator, respectively. The device exhibits an energy density of 44 Wh kg⁻¹ at 462 W kg⁻¹.

Abstract

The Al effect on the electrochemical properties of layered double hydroxides (LDHs) is not properly probed, although it is demonstrated to notably promote the capacitive behavior of LDHs. Herein, ternary NiCo₂Al _x layered double hydroxides with varying levels of Al stoichiometry are purposely developed, grown directly on mechanically flexible and electrically conducting carbon cloth (CC@NiCo₂Al _x ‐LDH). Al plays a significant role in determining the structure, morphology, and electrochemical behavior of NiCo₂Al _x ‐LDHs. At an increasing level of Al in NiCo₂Al _x ‐LDHs, there is a steady evolution from 1D nanowire to 2D nanosheets. The CC@NiCo₂Al‐LDH at an appropriate level of Al and with the nanowire–nanosheet mixed morphology exhibits both significantly enhanced electrochemical performance and excellent structural stability, with about a 2.3‐fold capacitance of NiCo₂‐OH. When applied as the anode in a flexible asymmetric supercapacitor (ASC), the CC@NiCo₂Al‐LDH gives rise to a remarkable energy density of 44 Wh kg⁻¹ at the power density of 462 W kg⁻¹, together with remarkable cyclic stability with 91.2% capacitance retention over 15 000 charge–discharge cycles. The present study demonstrates a new pathway to significantly improve the electrochemical performance and stability of transition metal LDHs, which are otherwise unstable in structure and poorly performing in both rate and cycling capability.

High‐performance ternary‐blend solar cells are fabricated by incorporating two nonfullerene acceptors. The enhanced power conversion efficiency mainly benefits from the broadened light harvesting and the optimized morphology. This work demonstrates that elaborately selecting a suitable third component with complementary basic properties is critical for the development of high‐performance ternary solar cells.

Abstract

Ternary polymer solar cells (PSCs) are one of the most promising device architectures that maintains the simplicity of single‐junction devices and provides an important platform to better tailor the multiple performance parameters of PSCs. Herein, a ternary PSC system is reported employing a wide bandgap polymeric donor (PBTA‐PS) and two small molecular nonfullerene acceptors (labeled as LA1 and 6TIC). LA1 and 6TIC keep not only well‐matched absorption profiles but also the rational crystallization properties. As a result, the optimal ternary PSC delivers a state of the art power conversion efficiency (PCE) of 14.24%, over 40% higher than the two binary devices, resulting from the prominently increased short‐circuit current density (J _sc) of 22.33 mA cm⁻², moderate open‐circuit voltage (V _oc) of 0.84 V, and a superior fill factor approaching 76%. Notably, the outstanding PCE of the ternary PSC ranks one of the best among the reported ternary solar cells. The greatly improved performance of ternary PSCs mainly derives from combining the complementary properties such as absorption and crystallinity. This work highlights the great importance of the rational design of matched acceptors toward highly efficient ternary PSCs.

High‐crystalline transition metal dichalcogenides nanosheets (including MoS₂, WS₂, MoSe₂, and WSe₂) can be massively synthesized with the reaction time of only several minutes through a molten salt method.

Abstract

2D transition metal dichalcogenides (TMDs) are well suited for energy storage and field–effect transistors because of their thickness‐dependent chemical and physical properties. However, as current synthetic methods for 2D TMDs cannot integrate both advantages of liquid‐phase syntheses (i.e., massive production and homogeneity) and chemical vapor deposition (i.e., high quality and large lateral size), it still remains a great challenge for mass production of high‐quality 2D TMDs. Here, a molten salt method to massively synthesize various high‐crystalline TMDs nanosheets (MoS₂, WS₂, MoSe₂, and WSe₂) with the thicknesses less than 5 nm is reported, with the production yield over 68% with the reaction time of only several minutes. Additionally, the thickness and size of the as‐synthesized nanosheets can be readily controlled through adjusting reaction time and temperature. The as‐synthesized MoSe₂ nanosheets exhibit good electrochemical performance as pseudocapacitive materials. It is further anticipates that this work will provide a promising strategy for rapid mass production of high‐quality nonoxides nanosheets for energy‐related applications and beyond.

Photovoltaic devices made from conjugated polymers now exhibit efficiencies rivaling amorphous silicon; however, the poor longevity of these devices continues to stymie their commercial impact. Copolymer additives represent a promising solution, yet little is known about how the copolymer sequence, composition, and concentration influence their compatibilizing abilities. Herein, random copolymer additives lead to higher efficiency and longer‐lasting photovoltaic devices.

Abstract

Recent advances have led to conjugated polymer‐based photovoltaic devices with efficiencies rivaling amorphous silicon. Nevertheless, these devices become less efficient over time due to changes in active layer morphology, thereby hindering their commercialization. Copolymer additives are a promising approach toward stabilizing blend morphologies; however, little is known about the impact of copolymer sequence, composition, and concentration. Herein, the impact of these parameters is determined by synthesizing random, block, and gradient copolymers with a poly(3‐hexylthiophene) (P3HT) backbone and side‐chain fullerenes (phenyl‐C₆₁‐butyric acid methyl ester (PC₆₁BM)). These copolymers are evaluated as compatibilizers in photovoltaic devices with P3HT:PC₆₁BM as the active layer. The random copolymer with 20 mol% fullerene side chains and at 8 wt% concentration in the blend gives the most stable morphologies. Devices containing the random copolymer also exhibit higher and more stable power conversion efficiencies than the control device. Combined, these studies point to the random copolymer as a promising new scaffold for stabilizing bulk heterojunction photovoltaics.

The fabrication of a shape memory high‐voltage supercapacitor with asymmetric nonaqueous electrolytes including redox additives for driving an integrated NO₂ gas sensor is demonstrated. Using an asymmetric organic electrolyte greatly enhances the performance of the supercapacitor. Furthermore, the supercapacitor and NO₂ gas sensor can be driven after several shape recoveries, successfully.

Abstract

A high‐voltage supercapacitor with shape memory for driving an integrated NO₂ gas sensor is fabricated using a Norland Optical Adhesive 63 polymer substrate, which can recover the original shape after deformation by short‐time heating. The supercapacitor consists of multiwalled carbon nanotube electrodes and organic electrolyte. By using organic electrolyte consisting of adiponitrile, acetonitrile, and dimethyl carbonate in an optimized volume ratio of 1:1:1, a high operation voltage of 2 V is obtained. Furthermore, asymmetric electrolytes with different redox additives of hydroquinone and 1,4‐dihydroxyanthraquinone to the anode and cathode, respectively, enhance both capacitance and energy density by ≈40 times compared to those of supercapacitor without redox additives. The fabricated supercapacitor on the Norland Optical Adhesive 63 polymer substrate retains 95.8% of its initial capacitance after 1000 repetitive bending cycles at a bending radius of 3.8 mm. Furthermore, the folded supercapacitor recovers its shape upon heating at 70 °C for 20 s. In addition, 90% of the initial capacitance is retained even after the 20th shape recovery from folding. The fabricated supercapacitor is used to drive integrated NO₂ gas sensor on the same Norland Optical Adhesive 63 substrate attached onto skin to detect NO₂ gas, regardless of deformation due to elbow movement.

Highly customizable all solution‐processed polymer light emitting diodes (PLEDs) are fabricated via a combination of inkjet and transfer printing of conductive polymer films. Such printing processes render highly customized electrode patterns for easy pixel definition and minimal solvent damage to underlying organic layers, respectively, thereby demonstrating various light‐emission logos and a passive matrix PLED array successfully for the first time.

Abstract

Inkjet and transfer printing processes are combined to easily form patterned poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films as top anodes of all solution–processed inverted polymer light emitting diodes (PLEDs) on rigid glass and flexible plastic substrates. An adhesive PEDOT:PSS ink is formulated and fully customizable patterns are obtained using the inkjet printing process. In order to transfer the patterned PEDOT:PSS films, adhesion properties at interfaces during multistep transfer printing processes are carefully adjusted. The transferred PEDOT:PSS film on the plastic substrates shows not only a sheet resistance of 260.6 Ω/□ and a transmittance of 92.1% at 550 nm wavelength but also excellent mechanical flexibility. The PLEDs with spin‐coated functional layers sandwiched between the transferred PEDOT:PSS top anodes and inkjet‐printed Ag bottom cathodes are fabricated. The fabricated PLEDs on the plastic substrates show a high current efficiency of 10.4 cd A⁻¹ and high mechanical stability. It is noted that because both Ag and PEDOT:PSS electrodes can be patterned with a high degree of freedom via the inkjet printing process, highly customizable PLEDs with various pattern sizes and shapes are demonstrated on the glass and plastic substrates. Finally, with all solution process, a 5 × 7 passive matrix PLED array is demonstrated.

Diketopyrrolopyrrole (DPP)‐based polymers have gained significant research interest in the organic electronics community. In this work, a combination of a DPP polymer derivative, PBDTT‐DPP, is used, blending with IEICO‐4F, a state‐of‐the‐art small‐molecule acceptor, yielding a champion power conversion efficiency of 9.66%, among the best performance of DPP‐based solar cells.

Abstract

The high crystallinity and ability to harvest near‐infrared photons make diketopyrrolopyrrole (DPP)‐based polymers one of the most promising donors for high performing organic solar cells (OSCs). However, DPP‐based OSC devices still suffer from the trade‐off between energetic loss (E _loss) and maximum external quantum efficiency (EQE_max), which significantly hinders their potential. Thus far, the replacement of fullerenes with small molecule acceptors did not wisdom the performance development of DPP‐donor‐based solar cells due to severe charge recombination issues. In this work, efficient DPP‐based solar cells are reported using low bandgap fused ring electron acceptor, IEICO‐4F. PBDTT‐DPP:IEICO‐4F OSC devices deliver a champion power conversion efficiency of 9.66% with successful interface engineering along with low E _loss of 0.57 eV and a high EQE_max (>70%).

In article number https://doi.org/10.1002/adfm.2019011711901171, Won Suk Shin, Jae Won Shim, and co‐workers report on ambient energy harvesting using organic photovoltaics (OPVs). The great indoor performance of the OPVs derived from their excellent optical and electrical properties allows them to serve as efficient semi‐permanent self‐powering systems for small‐scale low‐powered indoor electronic devices, including Internet of Things sensor nodes.

Sequentially processed organic photovoltaics (OPVs) using temperature‐dependent aggregation polymers where the acceptor materials have been processed using various nonorthogonal solvents provide almost similar performance in every single case. The superior performance when compared to their blend‐casting counterparts can be attributed to better control in morphology, which is critical for the large‐area scale‐up of OPVs.

Abstract

The conventional method to prepare bulk‐heterojunction organic photovoltaics (OPVs) is a one‐step method from the blend solution of donor and acceptor materials, known as blend‐casting (BC). Recently, an alternative method was demonstrated to achieve high efficiencies (13%) comparable to state‐of‐the‐art BC devices. This two‐step‐coating method, known as “sequential processing,” (SqP) involves sequential deposition of the donor and then the acceptor from two orthogonal solvents. However, the requirement of orthogonal solvents to process the donor and acceptor constrains the choice of materials and processing solvents. In this paper, an improved version of SqP method without the need for using orthogonal solvents is reported. The success is based on donor polymers with strong temperature‐dependent aggregation properties whose solution can be processed at a high temperature, but the resulting film becomes completely insoluble at room temperature, which allows for the processing of overlying acceptors from a wide range of nonorthogonal solvents. With this approach, efficient SqP OPVs is demonstrated based on a range of donor/acceptor materials and processing solvents, and, in every single case, SqP OPVs can outperform their BC counterparts. The results broaden the solvent choices and open a much larger window to optimize the processing parameters of SqP method.

O‐IDTBCN is a new nonfullerene acceptor that uses dicyanovinyl end groups to improve the electron mobility in blends with PTB7‐Th, relative to its predecessor, O‐IDTBR. Blends with O‐IDTBCN possess more balanced charge carrier mobilities, resulting in longer charge carrier lifetimes, which ultimately manifests in the attainment of fill factors of over 70% in devices.

Abstract

High fill factors have only recently become commonplace in nonfullerene‐based organic solar cells, with the balance of charge carrier mobilities often cited as the contributing factor. Here an end‐group modification to a commonly used nonfullerene acceptor (O‐IDTBR) is reported, in which the rhodanine end groups are replaced with dicyano moieties, resulting in the acceptor O‐IDTBCN. This new acceptor affords significant improvement in the fill factor (73%) and photocurrent (19.8 mA cm⁻²) in organic solar cells with the low bandgap polymer PTB7‐Th. A narrowing of the bandgap, as a result of greater push–pull hybridization, allows complementary absorption to the donor and thus improved photon harvesting. Additionally, the measurement of charge carrier mobilities and lifetimes in both systems reveal that the PTB7‐Th:O‐IDTBCN blend possesses more balanced charge carrier mobilities, and longer lifetimes. Morphology studies reveal a slightly greater degree of molecular mixing of the O‐IDTBCN when blended with PTB7‐Th, despite the greater and more balanced charge carrier mobilities in this blend.

High‐performance ternary‐blend solar cells are fabricated by incorporating two nonfullerene acceptors. The enhanced power conversion efficiency mainly benefits from the broadened light harvesting and the optimized morphology. This work demonstrates that elaborately selecting a suitable third component with complementary basic properties is critical for the development of high‐performance ternary solar cells.

Abstract

Ternary polymer solar cells (PSCs) are one of the most promising device architectures that maintains the simplicity of single‐junction devices and provides an important platform to better tailor the multiple performance parameters of PSCs. Herein, a ternary PSC system is reported employing a wide bandgap polymeric donor (PBTA‐PS) and two small molecular nonfullerene acceptors (labeled as LA1 and 6TIC). LA1 and 6TIC keep not only well‐matched absorption profiles but also the rational crystallization properties. As a result, the optimal ternary PSC delivers a state of the art power conversion efficiency (PCE) of 14.24%, over 40% higher than the two binary devices, resulting from the prominently increased short‐circuit current density (J _sc) of 22.33 mA cm⁻², moderate open‐circuit voltage (V _oc) of 0.84 V, and a superior fill factor approaching 76%. Notably, the outstanding PCE of the ternary PSC ranks one of the best among the reported ternary solar cells. The greatly improved performance of ternary PSCs mainly derives from combining the complementary properties such as absorption and crystallinity. This work highlights the great importance of the rational design of matched acceptors toward highly efficient ternary PSCs.

Diketopyrrolopyrrole (DPP)‐based polymers have gained significant research interest in the organic electronics community. In this work, a combination of a DPP polymer derivative, PBDTT‐DPP, is used, blending with IEICO‐4F, a state‐of‐the‐art small‐molecule acceptor, yielding a champion power conversion efficiency of 9.66%, among the best performance of DPP‐based solar cells.

Abstract

The high crystallinity and ability to harvest near‐infrared photons make diketopyrrolopyrrole (DPP)‐based polymers one of the most promising donors for high performing organic solar cells (OSCs). However, DPP‐based OSC devices still suffer from the trade‐off between energetic loss (E _loss) and maximum external quantum efficiency (EQE_max), which significantly hinders their potential. Thus far, the replacement of fullerenes with small molecule acceptors did not wisdom the performance development of DPP‐donor‐based solar cells due to severe charge recombination issues. In this work, efficient DPP‐based solar cells are reported using low bandgap fused ring electron acceptor, IEICO‐4F. PBDTT‐DPP:IEICO‐4F OSC devices deliver a champion power conversion efficiency of 9.66% with successful interface engineering along with low E _loss of 0.57 eV and a high EQE_max (>70%).