High-bandgap Layers Research Articles

Optimization of all inorganic perovskite solar cell with dual active layers for beyond 29% efficiency

This work presents the comparative analysis of the optimization and modelling of three perovskite solar cell configurations (PSC), single junction based ITO/ZnO/CsSnI3/Spiro-OMeTAD/Au and ITO/ZnO/Cs2BiAgI6/Spiro-OMeTAD/Au based single junction PSC while graded dual active layer based ITO/ZnO/CsSnI3/Cs2BiAgI6/Spiro-OMeTAD/Au configuration. The prime most threat to the performance of photovoltaic devices is the low absorption regime of the absorber layers based on the materials such as CsSnI3 (low band gap) and Cs2BiAgI6 (high band gap). However, with the inclusion of a graded absorber consisting of the combination of both the low and high band gap layers would significantly boost the performance efficiency of the PSC device. This study involves the adoption of SCAP-1D simulator for the modelling and analytical investigation of the performance of the proposed three PSC architectures. An optimized performance of 29.06 % power conversion efficiency, 32.06 mA/cm2 short circuit current density, 84.5% fill factor as well as 1.08 V open circuit voltage has been witnessed through the deployment of proposed graded dual active layer based PSC configuration which outreaches the Shockley-Queisser limit.

Dopant interactions and Mg segregation in (Al xGa 1− x) 0.5In 0.5P heterostructures

Acceptor atoms are experimentally observed to accumulate in the low bandgap layers of III–V heterostructures while being depleted from the high bandgap layers. Such acceptor segregation can be explained by considering the space charge neutrality condition in conjunction with hole segregation across the heterointerface. This approach reveals that the acceptor concentration ratio varies exponentially with valence band offset across the heterointerface, and further demonstrates that such acceptor segregation is suppressed by counterdoping the high bandgap layer with donor atoms. The same model can be used to explain enhanced acceptor solubility and suppressed acceptor diffusion in uniform composition samples that are counterdoped with donors. In each of these cases, the dopant concentrations (and hence dopant diffusion) are determined by the thermal equilibrium requirement that the Fermi energy be spatially invariant.

Device linearity comparisons between doped-channel and modulation-doped designs in pseudomorphic Al/sub 0.3/Ga/sub 0.7/As/In/sub 0.2/Ga/sub 0.8/As heterostructures

The linearities of pseudomorphic Al/sub 0.3/Ga/sub 0.7/As/In/sub 0.2/Ga/sub 0.8/As doped-channel FET's were characterized by comparing the characteristics of modulation-doped field-effect transistors (FET's) based on dc and microwave evaluations. By using an undoped high-bandgap layer beneath the gate, the so-called parasitic MESFET-type conduction, which is common in HEMT's, can therefore be eliminated in doped-channel designs. Therefore, a wide and flat device performance together with a high current driving capability can be achieved in DCFET's. This linearity improvement in device performance suggests that doped-channel designs are more suitable for application in microwave power devices.

Energy Up-Conversion at GaAs-GaInP2 and GaAs-AlGaInP2 Interfaces Caused by Cold Auger Processes

AbstractEfficient, low-temperature luminescence at energies far above that of the exciting cw-laser is reported at junctions of GaAs-GaInP2 and GaAs-AlxGa1−x.InP2. The signal originates from the high-band gap layers and disappears only if the excitation energy is tuned below the GaAs band gap, as monitored by up-converted photoluminescence excitation spectroscopy. This shows that the non-linear process is induced by the generation of electrons and holes in the GaAs. Furthermore, it is found that the up-conversion is only observed if the (A1)GaInP2 layers are CuPtB long-range ordered. The reason for this is the inherent presence of metastable states in these ordered alloys. It is argued that cold Auger processes cause the nonlinear effect at these type I interfaces.