Laser scribing is a promising technology for thin-film ablation in photovoltaic device manufacturing, particularly with non-conventional materials. This study explores copper oxides as alternative light absorbers due to their abundance and safe sourcing. Transition metal oxide (TMO) layers, like molybdenum oxide (MoO3), vanadium oxide (V2O5), and tungsten oxide (WO3), are investigated as selective contacts for advanced semiconductor devices. The research employs a high-powered fs laser (EKSPLA FemtoLux30, 30W, 1030 nm) with tunable pulse lengths (350 fs~1ps) and various wavelengths (1064, 532, and 355 nm) to determine the threshold ablation fluence and achieve optimal thin-film removal without substrate alteration. Diode isolation and electrical characteristics demonstrate the process's high quality.

At the junction between a metal and a semiconductor there are always charge transfer phenomena that can disrupt a selective or ohmic contact. This are result of workfunction mismatches either forming a Schottky junction or by Fermi Level Pinning. This effects unless they are used for a specific purpose within the device, can be detrimental to overall efficiency of a photovoltaic solar cell. Dipole thin films are known to modify surface energy being able to completely disrupt fermi level pinning and modify Schottky junction energy barrier. In this work a summary of several dipoles sharing some similarities between them such as PFN, PEI, DNA and PAMAM have been used to prove that upscaling the strength of dipole layers provide enhanced photovoltaic results when in combination with the metallic electrode.

Nowadays, the copper nitride (Cu N) is of great interest as a new solar absorber material, flexible and lightweight thin film solar cells. This material is a metastable semiconductor, non-toxic, composed of earth-abundant elements, and its band gap energy can be easily tunable in the range 1.4 to 1.8 eV. For this reason, it has been proposed for many applications in the solar energy conversion field. The main aim of this work is to evaluate the properties of the Cu N thin films fabricated by reactive radio-frequency (RF) magnetron sputtering at different RF power values to determine its potential as light absorber. The Cu N films were fabricated at room temperature (RT) from a Cu metallic target at the RF power ranged from 25 to 200 W on different substrates (silicon and glass). The pure nitrogen flux was set to 20 sccm, and the working pressures were set to 3.5 Pa and 5 Pa. The XRD results showed a transition from (100) to (111) preferred orientations when RF power increased; the AFM images revealed a granular morphology, while FTIR and Raman spectra exhibited the characteristics peaks related to Cu-N bonds, which became narrower when the RF power increased. Finally, to stablish the suitability of these films as absorber, the band gap energy was calculated from transmission spectra.

Copper nitride (Cu3N) has gained significant attention recently due to its potential in several scientific and technological applications. This study focuses on using Cu3N as a solar absorber in photovoltaic technology. Cu3N thin films were deposited on glass substrates and silicon wafers via radio-frequency magnetron sputtering at different nitrogen flow ratios with total pressures ranging from 1.0 to 5.0 Pa. The thin films’ structural, morphology, and chemical properties were determined using XRD, Raman, AFM, and SEM/EDS techniques. The results revealed that the Cu3N films exhibited a polycrystalline structure, with the preferred orientation varying from 100 to 111 depending on the working pressure employed. Raman spectroscopy confirmed the presence of Cu-N bonds in characteristic peaks observed in the 618–627 cm−1 range, while SEM and AFM images confirmed the presence of uniform and smooth surface morphologies. The optical properties of the films were investigated using UV-VIS-NIR spectroscopy and photothermal deflection spectroscopy (PDS). The obtained band gap, refractive index, and Urbach energy values demonstrated promising optical properties for Cu3N films, indicating their potential as solar absorbers in photovoltaic technology. This study highlights the favourable properties of Cu3N films deposited using the RF sputtering method, paving the way for their implementation in thin-film photovoltaic technologies. These findings contribute to the progress and optimisation of Cu3N-based materials for efficient solar energy conversion.

Development of carrier selective contacts for crystalline silicon solar cells has been recently of great interest toward the further expansion of silicon photovoltaics. The use of new electron and hole selective layers has opened an array of possibilities due to the low‐cost processing and non‐doping contacts. Here, a non‐doped heterojunction silicon solar cell without the use of any intrinsic amorphous silicon is fabricated using Deoxyribonucleic acid (DNA) as the electron transport layer (ETL) and transition metal oxide V 2 O 5 as the hole transport layer (HTL). The deposition and characterization of the DNA films on crystalline silicon have been studied, the films have shown a n ‐type behavior with a work function of 3.42 eV and a contact resistance of 28 mΩ cm 2 . This non‐doped architecture has demonstrated a power conversion efficiency of 15.6%, which supposes an increase of more than 9% with respect to the cell not containing the biomolecule, thus paving the way for a future role of nucleic acids as ETLs.

In this work we study conjugated polyelectrolyte (CPE) films based on polyamidoamine (PAMAM) dendrimers of generations G1 and G3. These fractal macromolecules are compared to branched polyethylenimine (b-PEI) polymer using methanol as the solvent. All of these materials present a high density of amino groups, which protonated by methoxide counter-anions create strong dipolar interfaces. The vacuum level shift associated to these films on n-type silicon was 0.93 eV for b-PEI, 0.72 eV for PAMAM G1 and 1.07 eV for PAMAM G3. These surface potentials were enough to overcome Fermi level pinning, which is a typical limitation of aluminium contacts on n-type silicon. A specific contact resistance as low as 20 mΩ·cm2 was achieved with PAMAM G3, in agreement with the higher surface potential of this material. Good electron transport properties were also obtained for the other materials. Proof-of-concept silicon solar cells combining vanadium oxide as a hole-selective contact with these new electron transport layers have been fabricated and compared. The solar cell with PAMAM G3 surpassed 15% conversion efficiency with an overall increase of all the photovoltaic parameters. The performance of these devices correlates with compositional and nanostructural studies of the different CPE films. Particularly, a figure-of-merit (Vσ) for CPE films that considers the number of protonated amino groups per macromolecule has been introduced. The fractal geometry of dendrimers leads to a geometric increase in the number of amino groups per generation. Thus, investigation of dendrimer macromolecules seems a very good strategy to design CPE films with enhanced charge-carrier selectivity.

The pursuit of efficient, profitable, and ecofriendly materials has defined solar cell research from its inception to today. Some materials, such as copper nitride (Cu3N), show great promise for promoting sustainable solar technologies. This study employed reactive radio-frequency magnetron sputtering using a pure nitrogen environment to fabricate quality Cu3N thin films to evaluate how both temperature and gas working pressure affect their solar absorption capabilities. Several characterization techniques, including X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), Raman spectroscopy, scanning electron microscopy (SEM), nanoindentation, and photothermal deflection spectroscopy (PDS), were used to determine the main properties of the thin films. The results indicated that, at room temperature, it is possible to obtain a material that is close to stoichiometric Cu3N material (Cu/N ratio ≈ 3) with (100) preferred orientation, which was lost as the substrate temperature increases, demonstrating a clear influence of this parameter on the film structure attributed to nitrogen re-emission at higher temperatures. Raman microscopy confirmed the formation of Cu-N bonds within the 628–637 cm−1 range. In addition, the temperature and the working pressure significantly also influence the film hardness and the grain size, affecting the elastic modulus. Finally, the optical properties revealed suitable properties at lower temperatures, including bandgap values, refractive index, and Urbach energy. These findings underscore the potential of Cu3N thin films in solar energy due to their advantageous properties and resilience against defects. This research paves the way for future advancements in efficient and sustainable solar technologies.

Poly(amidoamine) (PAMAM) dendrimers are used to modify the interface of metal-semiconductor junctions. The large number of protonated amines contributes to the formation of a dipole layer, which finally serves to form electron-selective contacts in silicon heterojunction solar cells. By modification of the work function of the contacts, the addition of the PAMAM dendrimer interlayer quenches Fermi level pinning, thus creating an ohmic contact between the metal and the semiconductor. This is supported by the observation of a low contact resistivity of 4.5 mΩ cm2, the shift in work function, and the n-type behavior of PAMAM dendrimer films on the surface of crystalline silicon. A silicon heterojunction solar cell containing the PAMAM dendrimer interlayer is presented, which achieved a power conversion efficiency of 14.5%, an increase of 8.3% over the reference device without the dipole interlayer.

This material can be considered to be an interesting eco-friendly choice to be used in the photovoltaic field. In this work, we present the fabrication of Cu3N thin films by reactive radio-frequency (RF) magnetron sputtering at room temperature, using nitrogen as the process gas. Different RF power values ranged from 25 to 200 W and gas pressures of 3.5 and 5 Pa were tested to determine their impact on the film properties. The morphology and structure were exhaustively examined by Atomic Force Microscopy (AFM), Fourier Transform Infrared (FTIR) and Raman Spectroscopies and X-ray Diffraction (XRD), respectively. The AFM micrographs revealed different morphologies depending on the total pressure used, and rougher surfaces when the films were deposited at the lowest pressure; whereas FTIR and Raman spectra exhibited the characteristics bands related to the Cu-N bonds of Cu3N. Such bands became narrower as the RF power increased. XRD patterns showed the (100) plane as the preferred orientation, that changed to (111) with the RF power, revealing a worsening in structural quality. Finally, the band gap energy was estimated from transmission spectra carried out with a Perkin Elmer 1050 spectrophotometer to evaluate the suitability of Cu3N as a light absorber. The values obtained demonstrated the capability of Cu3N for solar energy conversion applications, indicating a better film performance under the sputtering conditions 5.0 Pa and RF power values ranged from 50 to 100 W.

High open-circuit voltage in Sb2Se3 thin-film solar cells is a key challenge in the development of earth-abundant photovoltaic devices. CdS selective layers have been used as the standard electron contact in this technology. Long-term scalability issues due to cadmium toxicity and environmental impact are of great concern. In this study, we propose a ZnO-based buffer layer with a polymer-film-modified top interface to replace CdS in Sb2Se3 photovoltaic devices. The branched polyethylenimine layer at the ZnO and transparent electrode interface enhanced the performance of Sb2Se3 solar cells. An important increase in open-circuit voltage from 243 mV to 344 mV and a maximum efficiency of 2.4% was achieved. This study attempts to establish a relation between the use of conjugated polyelectrolyte thin films in chalcogenide photovoltaics and the resulting device improvements.

This work studies the use of thin layers of polyethylenimine (PEI) as an interface film to produce electron selective contacts for photovoltaic applications in crystalline silicon. Generally, in conjugated polyelectrolytes such as PEI with a high Lewis basicity, charge is accumulated along the chain of the polymer and counter anions from the solvent create an intense dipole array. In this work, part of the amine groups in PEI are protonated by the solvent that behaves as a weak Brønsted acid during the process. The PEI band modification is able to eliminate Fermi level pinning at metal/semiconductor junctions as it shifts the work function of the metallic electrode by more than 1 eV. As a consequence, induced charge transport between the metal and the semiconductor forms an electron accumulation region and promotes enhanced selectivity.

This work studies the use of polymeric layers of polyethylenimine (PEI) as an interface modification of electron-selective contacts. A clearly enhanced electrical transport with lower contact resistance and significant surface passivation (about 3 ms) can be achieved with PEI modification. As for other conjugated polyelectrolytes, protonated groups of the polymer with their respective counter anions from the solvent create an intense dipole. In this work, part of the amine groups in PEI are protonated by ethanol that behaves as a weak Bronsted acid during the process. A comprehensive characterization including high-resolution compositional analysis confirms the formation of a dipolar interlayer. The PEI modification is able to eliminate completely Fermi-level pinning at metal/ semiconductor junctions and shifts the work function of the metallic electrode by more than 1 eV. Induced charge transport between the metal and the semiconductor allows the formation of an electron accumulation region. Consequently, electron-selective contacts are clearly improved with a significant reduction of the specific contact resistance (less than 100 m omega.cm(2)). Proof-of-concept dopant-free solar cells on silicon were fabricated to demonstrate the beneficial effect of PEI dipolar interlayers. Full dopant-free solar cells with conversion efficiencies of about 14% could be fabricated on flat wafers. The PEI modification also improved the performance of classical high-efficiency heterojunction solar cells.

Sputtered films of reduced molybdenum oxide (MoOx) with a molybdenum trioxide target in different pressures and atmospheres were deposited in varying temperatures. Compositional, optic, and electric characteristics of the samples were studied. X-ray photoelectron spectroscopy revealed reduced states when working in the hydrogen + argon atmosphere implying that stoichiometry could be controlled by adding some hydrogen in the sputtering chamber. The effect of slightly increasing the substrate temperature during deposition was also studied and lead to the presence of metastable Mo4+ states at 3 mTorr. Optical properties match the ones already in the literature, and transmittances of 90% were achieved. The results support sputtering as a viable method of depositing MoOx films apart from thermal evaporation for many applications.

As optoelectronic devices continue to improve, control over film thickness has become crucial, especially in applications that require ultra-thin films. A variety of undesired effects may arise depending on the specific growth mechanism of each material, for instance a percolation threshold thickness is present in Volmer-Webber growth of materials such as silver. In this paper, we explore the introduction of aluminum in silver films as a mechanism to grow ultrathin metallic films of high transparency and low sheet resistance, suitable for many optoelectronic applications. Furthermore, we implemented such ultra-thin metallic films in Dielectric/Metal/Dielectric (DMD) structures based on Aluminum-doped Zinc Oxide (AZO) as the dielectric with an ultra-thin silver aluminum (Ag:Al) metallic interlayer. The multilayer structures were deposited by magnetron sputtering, which offers an industrial advantage and superior reliability over thermally evaporated DMDs. Finally, we tested the optimized DMD structures as a front contact for n-type silicon solar cells by introducing a hole-selective vanadium pentoxide (V2O5) dielectric layer.

Amorphous Silicon p-i-nphotodiodes were obtained by PECVD in a reactor with a rotating substrate holder. Reverse currents as low as 5 × 10−11 A/cm2 at a bias of − 2V were measured using a guard ring electrode to minimize lateral edge currents. The devices were degraded by a Xenon flash lamp in open circuit conditions. The kinetics of the degradation process was evaluated by studying the long time dark current transient under reverse bias.

Dielectric/metal/dielectric structures based on vanadium pentoxide with a thin silver interlayer have been optimized to replace traditional transparent electrodes. As would be expected, there is a tradeoff in the metal thickness to achieve high transparency and low sheet resistance simultaneously. It has been demonstrated that an ultra-thin gold seed prevents the tendency of silver to form clusters. This wetting effect reduces the metal thickness needed to form a continuous film, which leads to a higher averaged transmittance and very low sheet resistance. On the other hand, vanadium pentoxide on silicon forms a high-quality hole-selective contact. Thus, these structures can be used as an all-in-one transparent electrode and selective contact for a new kind of heterojunction solar cells. This concept has been proved in a 13.3% efficient solar cell fabricated on n-type silicon wafers. Besides being dopant-free, the complete fabrication route did not require any sputtered transparent electrode.

The use of solid particles as heat transfer fluid (HTF) presents a great potential to overcome drawbacks addressed in commercial Concentrated Solar Power (CSP) plants. The solid particles thermal energy storage (TES) system allows achieving both high thermal performance at high temperature and low cost from the material perspective. The conversion efficiency of CSP solid particles-based systems at high temperatures strongly depends on the optical properties and thermophysical properties of materials used both as HTF and as storage medium. The present study is aimed to provide more experimental data and evidences of the potential in using particulate solids for CSP application. The solar absorptance and the specific heat capacity of silicon carbide (SIC), silica sand (SiO2), and hematite (Fe2O3) are studied after different aging times at 750 degrees C and 900 degrees C. The solar absorptance slightly increases over the aging process except for the silica sand, which decreases its absorptance in the first 100 h, reaching a plateau. After the aging treatment, the specific heat capacity is increased for both SiC and silica sand. However, for the iron oxide the specific heat capacity is lower after aging. The black silicon carbide SiC is proven to be the best option to be used up to 900 degrees C as it shows the highest solar absorptance (96%) and the highest heat storage capacity.

In a previous paper, we reported that thin films of ZnO:Al [aluminum-zinc oxide (AZO)] deposited after achieving a very low base pressure [from 4.0×10–7 Torr (5.6×10–5 Pa) to 5.7×10–7 Torr (7.6×10–5 Pa)] result dark yellow in color and are resistive. These are undesirable characteristics for the application of AZO thin films as front electrodes in solar cells. However, given the increasingly tendency in the acquisition of equipment that allow us to reach excellent vacuum levels, it is necessary to find the deposition conditions that lead to an improving of transmittance without greatly impacting the electrical properties of materials deposited after achieving these levels of vacuum. In this way, the present work is focused on AZO thin films deposited after achieving a very low base pressure value: 4.2×10–7 Torr (5.6×10–5 Pa). For this, we studied the effect of the variation of the oxygen volume percent in the argon/oxygen mixture (by maintaining the deposition pressure constant) and the effect of deposition pressure with only argon gas on the main properties of AZO thin films. The depositions were done at room temperature on glass substrates by direct-current magnetron sputtering with a power of 120 W (corresponding to a power density of 2.63 W/cm2). As results, we found that the variation of deposition pressure with only argon gas is a good option for the control of optical and electrical properties, since the addition of oxygen, although improves transmittance, greatly impacts on the electrical properties. Furthermore, an interesting correlation was found between the optical and electrical properties and the chemical composition of the AZO films, the latter depending on the argon pressure (for this, a careful X-ray photoelectron spectroscopy analysis was performed). Also, the inverse relationship between crystallinity and deposition rate was confirmed, in which deposition rate inversely depends on argon pressure.

This paper reports on the effect of yttrium oxide as a novel treatment to improve the photoluminescence (PL) intensity and stability of porous silicon (PS). Yttrium oxide (Y 2 O 3 ) was incorporated into the PS layers by impregnation method using a saturated aqueous solution. The penetration of yttrium into the PS microstructure was examined using the Energy dispersive X-ray spectrometry (EDS) and the backscattered electron detector (BED-C) for composition imaging and analysis. The morphology of the front surface was studied using a field emission scanning electron microscope. The deposited yttrium oxide onto the PS layers was thermally activated to passivate efficiently the silicon dangling bonds, and prevent the PS from huge oxidation. The PL peak intensity of impregnated PS was increased noticeably compared to the as-prepared untreated PS. Unlike the as-prepared PS photoluminescence dependence with aging, the yttrium-passivated PS layers PL peak shows no shifts during aging allowing a high stability. Furthermore, we obtained a significant improvement of the effective minority carrier lifetime (τ eff ) after a short anneal at 600 °C, while increasing the temperature reduces noticeably the passivation properties. The improved surface passivation experienced after the thermal annealing can be ascribed to yttrium diffusion into the PS layer, with a resulting redistribution of yttrium oxide and subsequent passivation of silicon dangling bonds in the sub-interface region, this was confirmed by EDS analysis. The internal quantum efficiency measurements were performed to study the optoelectronic properties of the processed monocrystalline silicon substrates.