Systematic inspection on the interplay between MoNa-induced sodium and the formation of MoSe2 intermediate layer in CIGSe/Mo heterostructures.

The critical impact of sodium-doped molybdenum (MoNa) in shaping the MoSe2 interfacial layer, influencing the electrical properties of CIGSe/Mo heterostructures, and achieving optimal MoSe2 formation conditions, leading to improved hetero-contact quality. Notably, samples with a 600-nm-thick MoNa layer demonstrate the highest resistivity (73 µΩcm) and sheet resistance (0.45 Ω/square), highlighting the substantial impact of MoNa layer thickness on electrical conductivity. Controlled sodium diffusion through MoNa layers is essential for achieving desirable electrical characteristics, influencing Na diffusion rates, grain sizes, and overall morphology, as elucidated by EDX and FESEM analyses. Additionally, XRD results provide insights into the spontaneous peeling-off phenomenon, with the sample featuring a ~ 600-nm MoNa layer displaying the strongest diffraction peak and the largest crystal size, indicative of enhanced Mo to MoSe2 conversion facilitated by sodium presence. Raman spectra further confirm the presence of MoSe2, with its thickness correlating with MoNa layer thickness. The observed increase in resistance and decrease in conductivity with rising MoSe2 layer thickness underscore the critical importance of optimal MoSe2 formation for transitioning from Schottky to ohmic contact in CIGSe/Mo heterostructures. Ultimately, significant factors to the advancement of CIGSe thin-film solar cell production are discussed, providing nuanced insights into the interplay of MoNa and MoSe2, elucidating their collective impact on the electrical characteristics of CIGSe/Mo heterostructures.

Dopant engineering for ZnO electron transport layer towards efficient perovskite solar cells.

The conventional electron transport layer (ETL) TiO2 has been widely used in perovskite solar cells (PSCs), which have produced exceptional power conversion efficiencies (PCE), allowing the technology to be highly regarded and propitious. Nevertheless, the recent high demand for energy harvesters in wearable electronics, aerospace, and building integration has led to the need for flexible solar cells. However, the conventional TiO2 ETL layer is less preferred, where a crystallization process at a temperature as high as 450 °C is required, which degrades the plastic substrate. Zinc oxide nanorods (ZnO NRs) as a simple and low-cost fabrication material may fulfil the need as an ETL, but they still suffer from low PCE due to atomic defect vacancy. To delve into the issue, several dopants have been reviewed as an additive to passivate or substitute the Zn2+ vacancies, thus enhancing the charge transport mechanism. This work thereby unravels and provides a clear insight into dopant engineering in ZnO NRs ETL for PSC.

Elucidating the Effects of Interconnecting Layer Thickness and Bandgap Variations on the Performance of Monolithic Perovskite/Silicon Tandem Solar Cell by wxAMPS.

In this study, we investigated the pathways for integration of perovskite and silicon solar cells through variation of the properties of the interconnecting layer (ICL). The user-friendly computer simulation software wxAMPS was used to conduct the investigation. The simulation started with numerical inspection of the individual single junction sub-cell, and this was followed by performing an electrical and optical evaluation of monolithic 2T tandem PSC/Si, with variation of the thickness and bandgap of the interconnecting layer. The electrical performance of the monolithic crystalline silicon and CH3NH3PbI3 perovskite tandem configuration was observed to be the best with the insertion of a 50 nm thick (Eg ≥ 2.25 eV) interconnecting layer, which directly contributed to the optimum optical absorption coverage. These design parameters improved the optical absorption and current matching, while also enhancing the electrical performance of the tandem solar cell, which benefited the photovoltaic aspects through lowering the parasitic loss.

Metal organic framework derived NiO x nanoparticles for application as a hole transport layer in perovskite solar cells.

NiO x as a hole transport layer (HTL) has gained a lot of research interest in perovskite solar cells (PSCs), owing to its high optical transmittance, high power conversion efficiency, wide band-gap and ease of fabrication. In this work, four different nickel based-metal organic frameworks (MOFs) using 1,3,5-benzenetricarboxylic acid (BTC), terephthalic acid (TPA), 2-aminoterephthalic acid (ATPA), and 2,5-dihydroxyterephthalic acid (DHTPA) ligands respectively, have been employed as precursors to synthesize NiO x NPs. The employment of different ligands was found to result in NiO x NPs with different structural, optical and morphological properties. The impact of calcination temperatures of the MOFs was also studied and according to field emission scanning electron microscopy (FESEM), all MOF-derived NiO x NPs exhibited lower particle size at lower calcination temperature. Upon optimization, Ni-TPA MOF derived NiO x NPs calcined at 600 °C were identified to be the best for hole transport layer application. To explore the photovoltaic performance, these NiO x NPs have been fabricated as a thin film and its structural, optical and electrical characteristics were analyzed. According to the findings, the band energy gap (E g) of the fabricated thin film has been found to be 3.25 eV and the carrier concentration, hole mobility and resistivity were also measured to be 6.8 × 1014 cm-3; 4.7 × 1014 Ω cm and 2.0 cm2 V-1 s-1, respectively. Finally, a numerical simulation was conducted using SCAPS-1D incorporating the optical and electrical parameters from the thin film analysis. FTO/TiO2/CsPbBr3/NiO x /C has been utilized as the device configuration which recorded an efficiency of 13.9% with V oc of 1.89 V, J sc of 11.07 mA cm-2, and FF of 66.6%.

Probing the Interplay between Mo Back Contact Layer Deposition Condition and MoSe2 Layer Formation at the CIGSe/Mo Hetero-Interface.

The effect of Mo thin film deposition power in DC sputtering on the formation of a MoSe2 interfacial layer grown via the annealing of CIGSe/Mo precursors in an Se-free atmosphere was investigated. A Mo layer was deposited on glass substrates using the DC magnetron sputtering method. Its electrical resistivity, as well as its morphological, structural, and adhesion characteristics, were analyzed regarding the deposition power. In the case of thinner films of about 300 nm deposited at 80 W, smaller grains and a lower volume percentage of grain boundaries were found, compared to 510 nm thick film with larger agglomerates obtained at 140 W DC power. By increasing the deposition power, in contrast, the conductivity of the Mo film significantly improved with lowest sheet resistance of 0.353 Ω/square for the sample deposited at 140 W. Both structural and Raman spectroscopy outputs confirmed the pronounced formation of MoSe2, resulting from Mo films with predominant (110) orientated planes. Sputtered Mo films deposited at 140 W power improved Mo crystals and the growth of MoSe2 layers with a preferential (103) orientation upon the Se-free annealing. With a more porous Mo surface structure for the sample deposited at higher power, a larger contact area developed between the Mo films and the Se compound was found from the CIGSe film deposited on top of the Mo, favoring the formation of MoSe2. The CIGSe/Mo hetero-contact, including the MoSe2 layer with controlled thickness, is not Schottky-type, but a favourable ohmic-type, as evaluated by the dark I-V measurement at room temperature (RT). These findings support the significance of regulating the thickness of the unintentional MoSe2 layer growth, which is attainable by controlling the Mo deposition power. Furthermore, while the adhesion between the CIGSe absorber layer and the Mo remains intact, the resistance of final devices with the Ni/CIGSe/Mo structure was found to be directly linked to the MoSe2 thickness. Consequently, it addresses the importance of MoSe2 structural properties for improved CIGSe solar cell performance and stability.

Raytracing Modelling of Infrared Light Management Using Molybdenum Disulfide (MoS2) as a Back-Reflector Layer in a Silicon Heterojunction Solar Cell (SHJ).

The silicon heterojunction solar cell (SHJ) is considered the dominant state-of-the-art silicon solar cell technology due to its excellent passivation quality and high efficiency. However, SHJ's light management performance is limited by its narrow optical absorption in long-wave near-infrared (NIR) due to the front, and back tin-doped indium oxide (ITO) layer's free carrier absorption and reflection losses. Despite the light-trapping efficiency (LTE) schemes adopted by SHJ in terms of back surface texturing, the previous investigations highlighted the ITO layer as a reason for an essential long-wavelength light loss mechanism in SHJ solar cells. In this study, we propose the use of Molybdenum disulfide (MoS2) as a way of improving back-reflection in SHJ. The text presents simulations of the optical response in the backside of the SHJ applying the Monte-Carlo raytracing method with a web-based Sunsolve high-precision raytracing tool. The solar cells' electrical parameters were also resolved using the standard electrical equivalent circuit model provided by Sunsolve. The proposed structure geometry slightly improved the SHJ cell optical current density by ~0.37% (rel.), and hence efficiency (η) by about 0.4% (rel.). The SHJ cell efficiency improved by 21.68% after applying thinner back ITO of about 30 nm overlayed on ~1 nm MoS2. The efficiency improvement following the application of MoS2 is tentatively attributed to the increased NIR absorption in the silicon bulk due to the light constructive interface with the backside components, namely silver (Ag) and ITO. Study outcomes showed that improved SHJ efficiency could be further optimized by addressing front cell components, mainly front ITO and MoS2 contact engineering.

A Comparative Study on p- and n-Type Silicon Heterojunction Solar Cells by AFORS-HET.

Despite the increasing trend of n-type silicon wafer utilization in the manufacturing of high-efficiency heterojunction solar cells due to the superior advantages over p-type counterparts, its high manufacturing cost remains to be one of the most crucial factors, which impedes its market share growth with state-of-the-art silicon heterojunction (SHJ) solar cells demonstrating high conversion efficiencies from various configurations, the prospect of using an n-type wafer is debatable from a cost-efficiency point of view. Hence, a systematic comparison between p- and n-type SHJ solar cells was executed in this work using AFORS-HET numerical software. Front and rear-emitter architectures were selected for each type of wafer with ideal (without defects) and non-ideal (with defects) conditions. For ideal conditions, solar cells with p-type wafers and a front-emitter structure resulted in a maximum conversion efficiency of 28%, while n-type wafers demonstrated a maximum efficiency of 26% from the rear-emitter structure. These high-performance devices were possible due to the optimization of the bandgap and electron-affinity for all passivating and doping layers with values ranging from 1.3 to 1.7 eV and 3.9 to 4 eV, respectively. The correlation between the device structure and the type of wafers as demonstrated here will be helpful for the development of both types of solar cells with comparable performance.

High Quality CdS Thin Film Growth by Avoiding Anomalies in Chemical Bath Deposition for Large Area Thin Film Solar Cell Application.

Many high efficiency thin-film solar cells incorporate a thin layer of CdS in the device structure to form a heterojunction. Chemical bath deposition (CBD) is the most preferred method of deposition especially for large area thin film solar cells. This study explored the effects of ammonium sulfate on the CdS film produced by CBD using cadmium sulfate as the cadmium source. The concentration of ammonium sulfate was varied from 0 M up to 0.006 M. The resulting optical, structural and surface morphological properties of the films were characterized. Results have shown that the films obtained at higher concentrations of ammonium sulfate were smoother and the occurrence of pinholes was also reduced. Agglomeration of CdS particles that is usually present in films deposited using cadmium sulfate as a precursor was also noticeably reduced. It was also observed that the rate of deposition also increased, resulting in a thicker film for identical deposition time and temperature. The average thickness of the films produced ranged from 60 nm to 180 nm.