Abstract:CdTe thin film solar cells have demonstrated efficiencies over 20%, but CdTe has a somewhat higher band gap than optimal for single-junction terrestrial solar-cell power generation. A reduction in the band gap could therefore result in an overall improvement in performance. To reduce the band gap, selenium was alloyed with CdTe using a novel co-sublimation extension of the close-space-sublimation process. Co-sublimated layers of CdSeTe with various selenium concentrations were characterized for optical absorpt… Show more
“…The structure was identified to be the cubic zinc blende structure of CdTe, which agrees with previous experimental studies [10,18,19]. Secondary phases originating from Te 2 Se 2 O 8 , SeO 2 , and Se 2 O 5 based phases [20–22] cause Bragg reflections at 2θ angles of 12.6°, 19.9°, 30.6°, and 34.2° in the samples with composition x = 0.1, 0.3, 0.4, and 0.5.…”
Section: Resultssupporting
confidence: 89%
“…They follow Vegard’s law with a linear dependence on x , with the smaller size of Se compared to Te causing a decrease in lattice constant. The values are in agreement with literature [10,24], reinforcing the hypothesis that the peak splitting is caused by a small lattice distortion and thereby reduced symmetry.10.1080/14686996.2018.1497403-F0003Figure 3.Lattice constant of CdTe 1-x Se x thin films on glass substrate. The value for zinc blende CdSe ( x = 1) was taken from literature [23].…”
Section: Resultssupporting
confidence: 88%
“…In literature XRD patterns of CdTe 1-x Se x no peak splitting was observed [10]. Peak splitting can be an indicator of reduced symmetry, for example a distortion of the cubic lattice in one direction, resulting in a tetragonal crystal structure.…”
Section: Resultsmentioning
confidence: 99%
“…Alloying CdTe with Se is expected to change its performance as a solar cell absorber material in several aspects [10]. With Se having the same number of valence electrons as Te, substitution of the two does not introduce dopant-like acceptor or donor defects, but it can influence the behaviour of dopants such as Cu.…”
Section: Introductionmentioning
confidence: 99%
“…They showed that the reduced band gap of a CdTe 1-x Se x window layer translates to a gain in J
SC , but completely replacing the CdS window layer results in a V
OC loss. Swanson et al [10] studied solar cells with a CdTe 1-x Se x layer between a Mg 0.25 Zn 0.75 O window layer and the CdTe absorber layer. They also reported an increase in J
SC with a reduction in band gap.…”
The performance improvement of conventional CdTe solar cells is mainly limited by doping concentration and minority carrier life time. Alloying CdTe with an isovalent element changes its properties, for example its band gap and behaviour of dopants, which has a significant impact on its performance as a solar cell absorber. In this work, the structural, optical, and electronic properties of CdTe1-xSex films are examined for different Se concentrations. The band gap of this compound changes with composition with a minimum of 1.40 eV for x = 0.3. We show that with increasing x, the lattice constant of CdTe1-xSex decreases, which can influence the solubility of dopants. We find that alloying CdTe with Se changes the effect of Cu doping on the p-type conductivity in CdTe1-xSex, reducing the achievable charge carrier concentration with increasing x. Using a front surface CdTe1-xSex layer, compositional, structural and electronic grading is introduced to solar cells. The efficiency is increased, mostly due to an increase in the short-circuit current density caused by a combination of lower band gap and a better interface between the absorber and window layer, despite a loss in the open-circuit voltage caused by the lower band gap and reduced charge carrier concentration.
“…The structure was identified to be the cubic zinc blende structure of CdTe, which agrees with previous experimental studies [10,18,19]. Secondary phases originating from Te 2 Se 2 O 8 , SeO 2 , and Se 2 O 5 based phases [20–22] cause Bragg reflections at 2θ angles of 12.6°, 19.9°, 30.6°, and 34.2° in the samples with composition x = 0.1, 0.3, 0.4, and 0.5.…”
Section: Resultssupporting
confidence: 89%
“…They follow Vegard’s law with a linear dependence on x , with the smaller size of Se compared to Te causing a decrease in lattice constant. The values are in agreement with literature [10,24], reinforcing the hypothesis that the peak splitting is caused by a small lattice distortion and thereby reduced symmetry.10.1080/14686996.2018.1497403-F0003Figure 3.Lattice constant of CdTe 1-x Se x thin films on glass substrate. The value for zinc blende CdSe ( x = 1) was taken from literature [23].…”
Section: Resultssupporting
confidence: 88%
“…In literature XRD patterns of CdTe 1-x Se x no peak splitting was observed [10]. Peak splitting can be an indicator of reduced symmetry, for example a distortion of the cubic lattice in one direction, resulting in a tetragonal crystal structure.…”
Section: Resultsmentioning
confidence: 99%
“…Alloying CdTe with Se is expected to change its performance as a solar cell absorber material in several aspects [10]. With Se having the same number of valence electrons as Te, substitution of the two does not introduce dopant-like acceptor or donor defects, but it can influence the behaviour of dopants such as Cu.…”
Section: Introductionmentioning
confidence: 99%
“…They showed that the reduced band gap of a CdTe 1-x Se x window layer translates to a gain in J
SC , but completely replacing the CdS window layer results in a V
OC loss. Swanson et al [10] studied solar cells with a CdTe 1-x Se x layer between a Mg 0.25 Zn 0.75 O window layer and the CdTe absorber layer. They also reported an increase in J
SC with a reduction in band gap.…”
The performance improvement of conventional CdTe solar cells is mainly limited by doping concentration and minority carrier life time. Alloying CdTe with an isovalent element changes its properties, for example its band gap and behaviour of dopants, which has a significant impact on its performance as a solar cell absorber. In this work, the structural, optical, and electronic properties of CdTe1-xSex films are examined for different Se concentrations. The band gap of this compound changes with composition with a minimum of 1.40 eV for x = 0.3. We show that with increasing x, the lattice constant of CdTe1-xSex decreases, which can influence the solubility of dopants. We find that alloying CdTe with Se changes the effect of Cu doping on the p-type conductivity in CdTe1-xSex, reducing the achievable charge carrier concentration with increasing x. Using a front surface CdTe1-xSex layer, compositional, structural and electronic grading is introduced to solar cells. The efficiency is increased, mostly due to an increase in the short-circuit current density caused by a combination of lower band gap and a better interface between the absorber and window layer, despite a loss in the open-circuit voltage caused by the lower band gap and reduced charge carrier concentration.
Low‐cost solution‐processed CdTe nanocrystal (NC) solar cells always suffer from a high interface energy barrier and unbalanced hole/electron transport as well as anisotropic atom diffusion on the CdTe surface due to the limited amount of hole/electron interface materials or the difficulty in interface processing. In this work, a novel strategy is first adopted with gradient electron transport layer (CdS/CdSe) modification in the cathode and a new crosslinkable hole transport polymer (P‐TPA) implantation in the anode. The carrier recombination at interfaces is greatly decreased and thus the carrier collection is increased. Moreover, the light harvesting is improved both in short and long wavelength regions, making Jsc and Voc increase simultaneously. A champion solar cell shows a very high power conversion efficiency of 9.2% and an outstanding Jsc of 25.31 mA cm−2, which are among the highest values for all solution‐processed CdTe NC solar cells with a superstrate structure, and the latter value is even higher than that of traditional thick CdTe thin‐film solar cells (2 µm) via the high temperature close space sublimation method. This work demonstrates that facile surface modifications in both the cathode and anode with stepped extraction and organic–inorganic hybridization are very promising in constructing next‐generation highly efficient NC photovoltaic devices.
Black phosphorus was first synthesized by Bridgman in 1914 [1] but has been less intensively studied in the past century due The successful isolation of phosphorene (atomic layer thick black phosphorus) in 2014 has currently aroused the interest of 2D material researchers. In this review, first, the fundamentals of phosphorus allotropes, phosphorene, and black phosphorus, are briefly introduced, along with their structures, properties, and synthesis methods. Second, the readers are presented with an overview of their energy applications. Particularly in electrochemical energy storage, the large interlayer spacing (0.53 nm) in phosphorene allows the intercalation/deintercalation of larger ions as compared to its graphene counterpart. Therefore, phosphorene may possess greater potential for high electrochemical performance. In addition, the status of lithium ion batteries as well as secondary sodium ion batteries is reviewed. Next, each application for energy generation, conversion, and storage is described in detail with milestones as well as the challenges. These emerging applications include supercapacitors, photovoltaic devices, water splitting, photocatalytic hydrogenation, oxygen evolution, and thermoelectric generators. Finally the fast-growing dynamic field of phosphorene research is summarized and perspectives on future possibilities are presented calling on the efforts of chemists, physicists, and material scientists
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