Although III–V compound semiconductor multi‐junction cells show the highest efficiency among all types of solar cells, their cost is quite high due to expensive substrates, long epitaxial growth and complex balance of system components. To reduce the cost, ultra‐thin films with advanced light management are desired. Here effective light trapping in freestanding thin film nanopyramid arrays is demonstrated and multiple‐times light path enhancement is realized, where only 160 nm thick GaAs with nanopyramid structures is equivalent to a 1 μm thick planar film. The GaAs nanopyramids are fabricated using a combination of nanosphere lithography, nanopyramid metal organic chemical vapor deposition (MOCVD) growth, and gas‐phase substrate removal processes. Excellent optical absorption is demonstrated over a broad range of wavelengths, at various incident angles and at large‐curvature bending. Compared to an equally thick planar control film, the overall number of photons absorbed is increased by about 100% at various incident angles due to significant antireflection and light trapping effects. By implementing these nanopyramid structures, III–V material usage and deposition time can be significantly reduced to produce high‐efficiency, low‐cost thin film III–V solar cells.
State-of-the-art III-V multijunction cells have achieved a record efficiency of 42,8%, which has fueled great interest in the utility sector for large-scale deployment. However, III-V solar cells have thus far proven too expensive for widespread terrestrial applications due to the combined cost of substrates, growth processes, and materials. Here, we propose a novel III-V solar cell based on the epitaxial growth of AIGaAs/GaAs on Ge nanowires, pre-patterned on low cost substrates to achieve cost-effective, large scale deployment. This approach is based on our recent discovery that the surface kinetics and epitaxial growth by MBE and MOCVD are dramatically altered when growing on nanostructures instead of planar surfaces. These growth kinetics enable uniform, single crystal growth of low-defect, lattice mismatched materials on nano structures with high aspect ratios.We present the device design, TCAD simulation results, and experimental growth results for GaAs/Ge core-shell nanowires on silicon substrates. Finite-difference time domain (FDTD) simulation results show that this GaAs/Ge nanowire array has reduced reflection and wider incident angle acceptance than its planar counterpart, and outperforms planar anti-reflective coatings under some conditions. GaAs is epitaxially grown on Ge nanowires via MBE and MOCVD. TE M measurements on the wires confirm that the GaAs/Ge core-shell structure is single crystal. Based on these results, we are in the process of fabricating GaAs/Ge nanowire solar cell arrays. We will present further characterization of these core-shell arrays as well as electrical measurements of solar cell devices.
The first measurement of the top quark pair ($$ \textrm{t}\overline{\textrm{t}} $$
t
t
¯
) production cross section in proton-proton collisions at $$ \sqrt{s} $$
s
= 13.6 TeV is presented. Data recorded with the CMS detector at the CERN LHC in Summer 2022, corresponding to an integrated luminosity of 1.21 fb−1, are analyzed. Events are selected with one or two charged leptons (electrons or muons) and additional jets. A maximum likelihood fit is performed in event categories defined by the number and flavors of the leptons, the number of jets, and the number of jets identified as originating from b quarks. An inclusive $$ \textrm{t}\overline{\textrm{t}} $$
t
t
¯
production cross section of 881 ± 23 (stat + syst) ± 20 (lumi) pb is measured, in agreement with the standard model prediction of $$ {924}_{-40}^{+32} $$
924
−
40
+
32
pb.
Transport and photoresponse properties of the heterostructure consisting of a Pr0.5Ca0.5CoO3 film and a Nb-SrTiO3 substrate were investigated. The Pr0.5Ca0.5CoO3 film exhibits semiconducting behavior and the resistances are decreased when irradiated by a 532 nm laser. The rectifying behaviors are observed in the heterostructure. The ideality factors and the diffusion voltages monotonically decrease with increasing the temperature. The photovoltatges of the heterostructure under the irradiation approach the saturation at about . The minority carrier lifetime of is estimated from the time response properties in the falling process of photovoltages. These results reveal that the Pr0.5Ca0.5CoO3 heterostructures have great potentials in photoresponse and photoelectric conversion applications.
III–V compound semiconductor multi‐junction solar cells are the most efficient of all solar cells. However, in order to reduce high costs, ultra‐thin films with advanced light management are desired. , James S. Harris, Yi Cui, Dong Liang, and co‐workers report that a 160‐nm‐thick GaAs thin film of nanopyramid arrays on flexible transparent superstrates demonstrates excellent optical absorption properties. Due to significant antireflection and light trapping effects, the double‐sided nanostructures enhance the photon absorption in the thin film by over 80% at near normal incidence and over 100% at 40–70° incidence.
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