The three thermal rate equations were built newly up at both ends and at the junction of a p–n diode, in order to derive analytically the temperature difference ΔT (between a junction and both ends) and the internal cooling efficiency η defined newly for a homojunction diode. The maxima ΔT and η of a diode were derived analytically as a function of Vj within the short-length approximation and calculated numerically as a function of Vj or Vbi, where Vj is a voltage across the junction and Vbi is a built-in voltage at the junction. As a result, ΔT increases abruptly with an increase of Vj below Vj=0.050 V or of Vbi below Vbi=0.10 V, while above their values, it increases slowly with an increase of Vj or Vbi to saturate a certain value. For example, ΔT was estimated as 14.6 K for Hg0.8Cd0.2Te diode with Vbi=0.36 V. η has a local maximum of 63% at Vj≈0.01 V or at Vbi≈0.03 V, while above their respective values, it decreases abruptly with an increase of Vj or Vbi and falls to 4.4% at Vbi=0.80 V which is equivalent to that of a diode emitting a laser for fiber optical communication. However, the greater enhancements
in ΔT and η of a diode are required to apply the internal cooling system to a laser-emitting diode which needs the exact control of temperature.
These results should be useful for the application of the internal cooling system to the double heterojunction diode used
in the optical communication. 相似文献
Single material organic solar cells become an interesting area of research to overcome the challenges with efficient charge separation efficiencies in conventional organic solar cells. In this article, we have synthesized nonmetallated and metallated porphyrin‐fullerene dyad materials (H2P‐C60 and ZnP‐C60, respectively) with simple structure, comprehensively studied their charge transfer mechanism, and established a proof of concept that nonmetallated porphyrin‐fullerene dyads are better candidates to be used in organic solar cells compared with metallated dyads. Absorption and electrochemical analysis revealed the ground state electronic interactions between donor‐acceptor moieties in both types of dyads. Driving force (?ΔGoET) for intramolecular electron transfer process was calculated by first oxidation and reduction potentials of dyads. The excited state electronic interactions were characterized by time‐resolved fluorescence and pump‐probe transient absorption experiments. Strong fluorescence quenching of porphyrin along with reduced lifetimes in dyads due to deactivation of singlet excited states by photoinduced charge transfer process between porphyrin/Zn‐porphyrin core and fullerene in different polarity solvents was observed. Transient absorption spectroscopy was also applied to identify the transient spectral features, ie, cationic (H2P+/ZnP+) and anionic (C60?) radicals formed because of the charge separation in both types of dyads. Finally, organic solar cell device was also fabricated using the dyads. We obtained higher Voc, Jsc, and fill factor in single material organic solar cell using H2P‐C60 compared to previous reports. 相似文献
The present study investigates the electrical properties of transition metal oxide (TMO) emitters in dopant‐free n‐Si back contact solar cells by comparing the properties of solar cells employing three TMOs (WOx, MoOx and V2Ox) with varying electrical properties acting as p‐type contacts. The TMOs are found to induce large band bending in n‐Si, which reduces the injection level dependent interfacial recombination speed Seff and contact resistivity ρc. Among the TMO/n‐Si contacts considered, the V2Ox/n‐Si contact achieves the lowest Seff of 138 cm/s and ρc of 0.034 Ω cm2, providing the significant advantages over heavily doped a‐Si:H(p)/n‐Si contacts. The best device performance was achieved by the V2Ox/n‐Si solar cell, demonstrating an efficiency of 16.59% and an open‐circuit voltage of 610 mV relative to solar cells based on MoOx/n‐Si (15.09%, 594 mV) and WOx/n‐Si (12.44%, 539 mV). Furthermore, the present work is the first to employ WOx, V2Ox and Cs2CO3 in back contact solar cells. The fabrication process employed offers great potential for the mass production of back contact solar cells owing to simple, metal mask patterning with high alignment quality and dopant‐free steps conducted at a lower temperature. 相似文献
An ultrathin Mg(OH)2 layer was solution‐deposited onto the ZnO nanowires to solve the problem of interfacial charge recombination, caused by the increase of interfacial area in bulk heterojunction (BHJ) PbS colloidal quantum dot solar cells (CQDSCs). This Mg(OH)2 interlayer efficiently passivated the surface defects of ZnO nanowires and provided tunnel barrier at ZnO/PbS interface. As a result, the charge recombination at ZnO/PbS interface was largely suppressed, proved by the significantly elongated electron lifetime and the increased open‐circuit voltage of the Mg(OH)2‐involved BHJ CQDSCs. Careful thickness optimization of Mg(OH)2 interlayer finally brought a ~33% increase in Voc and ~25% improvement in power conversion efficiency. 相似文献
The N-channel metal oxide semiconductor field effect transistors (MOSFETs) were exposed to 95 MeV oxygen ions in the fluence range of 5 × 1010 to 5 × 1013 ions/cm2. The influence of ion irradiation on threshold voltage (VTH), linear drain current (IDLin), leakage current (IL), drain conductance (gD), transconductance (gm), mobility (μ) and drain saturation current (IDSat) of MOSFETs was studied systematically for various fluence. The VTH of the irradiated MOSFET was found to decrease significantly after irradiation. The interface (Nit) and oxide trapped charge (Not) were estimated from the subthreshold measurements and were found to increase after irradiation. The densities of oxide-trapped (ΔNit) charge in irradiated MOSFETs were found to be higher than those of the interface trapped charge (ΔNot). The IDLin and IDSat of MOSFETs were also found to decrease significantly after irradiation. Studies on effects of 95 MeV oxygen ion irradiation on gm, gD and μ show a degradation varying from 70 to 75% after irradiation. The mobility degradation coefficients for Nit(αit) and Not(αit) were estimated. The results of these studies are presented and discussed. 相似文献
An organic–inorganic hybrid solar cell based on CdSe quantum dots (QDs) and poly(3-hexylthiophene) (P3HT) was fabricated. Its temperature-dependent photovoltaic behaviors, such as I–V characteristic curves and open circuit voltage (Voc) transient response, were measured. The photovoltaic behavior of this hybrid thin film device was similar with that of organic thin film solar cells, according to analysis results based on the equivalent circuit method. The exact carrier lifetime was remarkably different between under low-temperature region and under temperature above 197 K. 相似文献
Alkali‐free Cu(In,Ga)Se2(CIGS) absorbers grown on Mo‐coated alumina (Al2O3) substrates were doped with potassium (K) after CIGS growth by a potassium fluoride (KF) post‐deposition treatment (PDT). The addition of K to the absorber leads to a strong increase in cell efficiency from 10.0% for the K‐free cell to 14.2% for the K‐doped cell, mainly driven by an increase in the open‐circuit voltage Voc and the fill factor FF, and to an increase in the net charge carrier density. Hence K doping by KF‐PDT is comparable to doping with Na.