Thin TiO2 films are demonstrated to be an excellent electron-selective contact for crystalline silicon solar cells. An efficiency of 21.6% is achieved for crystalline silicon solar cells featuring a full-area TiO2 -based electron-selective contact.

We report on the fabrication and characterization of solar blind photodetectors (SBPs) based on undoped β‐Ga2O3 and Zn doped (∼5 × 1020 cm−3) β‐Ga2O3 (ZnGaO) epitaxial films with cutoff wavelength of ∼260 nm. The epilayers were grown on c‐sapphire by the metal organic chemical vapor deposition technique and their structural, electrical and optical properties were characterized using various methods. As grown films have a large number of defects, resulting in detectors with enhanced internal gain, hence, high spectral responsivity >103 A/W. Post growth annealing in oxygen improved the quality of the epilayers, leading to detectors with reduced dark current (∼nA to ∼pA) and increased out of band rejection ratio. At 20 V bias, a ZnGaO detector showed a peak responsivity of 210 A/W (at 232 nm) and an out of band rejection ratio (i.e., R232 nm/R320 nm) of 5 × 104. Alternatively, for a β‐Ga2O3 detector these parameters were found to be five times and three times lower, respectively, suggesting that ZnGaO detectors have superior performance characteristics. These results provide a roadmap toward achieving high responsivity SBPs based on epitaxial ZnGaO films, laying a solid foundation for future applications.

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In this study, the cross-section of electron-selective titanium oxide (TiO2) contacts for n-type crystalline silicon solar cells were investigated by transmission electron microscopy. It was revealed that the excellent cell efficiency of 21.6% obtained on n-type cells, featuring SiO2/TiO2/Al rear contacts and after forming gas annealing (FGA) at 350°C, is due to strong surface passivation of SiO2/TiO2 stack as well as low contact resistivity at the Si/SiO2/TiO2 heterojunction. This can be attributed to the transformation of amorphous TiO2 to a conducting TiO2-x phase. Conversely, the low efficiency (9.8%) obtained on cells featuring an a-Si:H/TiO2/Al rear contact is due to severe degradation of passivation of the a-Si:H upon FGA.

Para-, or 4-nitrophenol, and related nitroaromatics are broadly used compounds in industrial processes and as a result are among the most common anthropogenic pollutants in aqueous industrial effluent; this requires development of practical remediation strategies. Their catalytic reduction to the less toxic and synthetically desirable aminophenols is one strategy. However, to date, the majority of work focuses on catalysts based on precisely tailored, and often noble metal-based nanoparticles. The cost of such systems hampers practical, larger scale application. We report a facile route to bulk cobalt oxide-based materials, via a combined mechanochemical and calcination approach. Vibratory ball milling of CoCl2(H2O)6 with KOH, and subsequent calcination afforded three cobalt oxide-based materials with different combinations of CoO(OH), Co(OH)2, and Co3O4 with different crystallite domains/sizes and surface areas; Co@100, Co@350 and Co@600 (Co@###; # = calcination temp). All three prove active for the catalytic reduction of 4-nitrophenol and related aminonitrophenols. In the case of 4-nitrophenol, Co@350 proved to be the most active catalyst, therein its retention of activity over prolonged exposure to air, moisture, and reducing environments, and applicability in flow processes is demonstrated.

alignment for charge transport. [11] TMOs have work functions ranging from 3 (ZrO 2) to 7 eV (V 2 O 5), making them suitable candidates for energy-level alignment in a variety of devices. [12] In crystalline silicon (c-Si) solar cells, TMOs are being used as transparent, dopant-free heterocontacts to the silicon absorber. [13] These have the potential to replace the heavily doped contacts found in current state-of-the-art heterojunction solar cells, [14,15] which can suffer from parasitic optical absorption and increased Auger recombination at the silicon surface. [16,17] TMOs are commonly deposited using different physical vapor deposition (PVD) techniques such as thermal evaporation and sputtering. [18,19] Atomic layer deposition (ALD) has emerged as an alternative for TMO deposition. [20] ALD offers greater thickness control and uniformity than PVD due to its reaction-limited growth process, making it ideal for applications requiring ultra-thin, conformal oxides on textured silicon surfaces. [21-24] While this technique has many advantages over PVD, depending on molecular precursor choice, it may require "energy enhancement" of the oxidant pulse, most commonly in the form of plasma or ozone, to achieve efficient growth. [25] Additionally, the growth rate of ALD is typically on the order of angstroms per Molybdenum oxide thin films are successfully deposited using spatial atomic layer deposition (SALD), a tool designed for high-throughput industrial film growth. The structural and optical properties of the film are evaluated using ultraviolet photoelectron spectroscopy, high-resolution transmission electron microscopy, and spectroscopic ellipsometry. To demonstrate the applicability of molybdenum oxide in industrial settings the films are applied as holeselective silicon heterojunction contacts for solar cells. When paired with intrinsic amorphous silicon passivation layers, implied open-circuit voltages of 699 mV are achieved. The carrier transport is unaffected by low-temperature contact anneals up to 300 °C with contact resistivities of ≈ 10 mΩ cm 2. Finally, the optical performance of silicon solar cells featuring different front hole-selective heterojunction structures are simulated. It is shown that the generation current density of heterojunction solar cells can be significantly increased with the addition of SALD molybdenum oxide contacts.

In this study, a molybdenum oxide (MoO x ) and aluminum (Al) contact structure for crystalline silicon (c-Si) solar cells is investigated using a combination of transmission line measurements (TLM) and in-situ transmission electron microscopy (TEM). Cross-sectional high-resolution TEM (HRTEM) micrographs reveal a %2 nm silicon oxide (SiO x ) interlayer at c-Si/ MoO x interface in the as-deposited state, indicating that formation of SiO x occurs during deposition of MoO x . Moreover, oxygen diffusion takes place from MoO x toward Al resulting in the formation of a %2-3 nm aluminum oxide (AlO x ) interlayer at the MoO x /Al interface. Overall, it is observed that MoO x /Al contact is relatively stable upon annealing up to 200 C and still retains ohmic transport with sufficiently low contact resistivity.

In this study, the thermal stability of a contact structure featuring hole-selective tungsten oxide (WOx) and aluminum deposited onto p-type crystalline silicon (c-Si/WOx/Al) was investigated using a combination of transmission line measurements (TLM) and in situ transmission electron microscopy (TEM) studies. The TEM images provide insight into why the charge carrier transport and recombination characteristics change as a function of temperature, particularly as the samples are annealed at temperatures above 500 °C. In the as-deposited state, a ≈ 2 nm silicon oxide (SiOx) interlayer forms at the c-Si/WOx interface and a ≈ 2–3 nm aluminum oxide (AlOx) interlayer at the WOx/Al interface. When annealing above 500 °C, Al diffusion begins, and above 600 °C complete intermixing of the SiOx, WOx, AlOx and Al layers occurs. This results in a large drop in the contact resistivity, but is the likely reason surface recombination increases at these high temperatures, since a c-Si/Al contact is basically being formed. This work provides some fundamental insight that can help in the development of WOx films as hole-selective rear contacts for p-type solar cells. Furthermore, this study demonstrates that in situ TEM can provide valuable information about thermal stability of transition metal oxides functioning as carrier-selective contacts in silicon solar cells.