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We present a comprehensive comparative analysis of acid textured and MACE (Metal Assisted Chemical Etching) nano-textured multi crystalline silicon (mc-Si) solar cells processed in an industrial cell line in terms of performance parameters. The batch average open circuit voltage of nano-textured solar cells was marginally lower and the measures for improving the same are discussed. Batch average short circuit current (J S C ) and fill factor (FF) were respectively 0.65 mA-cm−2 and 0.7% (absolute) higher for MACE nano-textured solar cells. Significantly lower surface reflectance in MACE nano-textured cells in the blue and near infrared regions are found to be the reason for the enhancement in J S C . The main component of FF gain is identified as the lower series resistance in MACE cells. The contact formation mechanism in screen printed mc-Si solar cells, investigated using scanning electron microscopy, revealed that the elevated portions at the boundaries of the textures act as favorable sites for silver crystallite precipitation. A larger areal density of such sites is observed on the MACE nano-textured surface than in case of acid textured solar cells, leading to a much lower series resistance. The results suggest the potential for the application of MACE in the more popular mono-crystalline silicon cell technology for further reduction of contact resistance. Alternatively, MACE may be used to obtain similar contact resistance with lower amount of silver paste, compared to iso- and pyramid textured solar cells.

Carrier selective contact (CSC) architecture is one of several promising candidates for high-efficiency silicon solar cells operating close to the thermodynamic limit. However, an industrially feasible process is lacking for manufacturable CSC cells. Specifically, although evaporated molybdenum oxide (MoOx) has been actively researched as a hole selective layer, a more industry-compatible deposition process is critically needed. Atomic layer deposition (ALD) has been widely employed in the industry for material stacks requiring precise thickness control and uniformity. In this paper, we present a performance analysis of CSC solar cells fabricated using ALD MoOx as the hole selective layer. As a first step, the standard ALD recipe was modified to obtain sub-stoichiometric MoOx with a higher work function due to increased oxygen vacancy concentration. The modified MoOx recipe resulted in low open-circuit voltage values in fabricated not-passivated CSC solar cells. A 4 nm thick amorphous silicon layer inserted in the hole selective stack showed significant improvement in minority lifetime but worse solar cell performance due to increased series resistance. Besides indicating a strong trade-off between passivation and series resistance, the solar cell data highlights series resistance as a key performance limiter in CSC solar cells.

Variation in electrical performance measurement of industrial crystalline Si (c-Si) solar cells is commonly observed. The probable reasons include non-uniform illumination, spectral mismatch, shadow due to dissimilar probing bars and probing schemes incompatible to cell front metal contact design. In the present work, we have studied the impact of shadow of probing bars on the I-V measurement of Al-BSF c-Si test solar cell. The shadow created due to fixed width of probe bars (PB) reduce the current generation along the contact bus bars (BB). A correction factor is devised for shadow loss in short circuit current of the test cell and applied in the I-V measurements. Additionally, we observed the variation in correction factor due to the difference in BB and PB width resulted in the difference in power loss even contacting using the same bus bars. In conclusion, we have successfully applied shadow correction in our I-V testing facility (B) and reduced the magnitude of variation from 2.75% to 0.25% in solar cell performance when compared with other testing facility (A).

Silver (Ag) based front contact metallisation is a crucial process step in industrial Si solar cell fabrication. Lesser front metal coverage leads to high resistive losses, whereas higher coverage results in shadowing loss as well as increased metal-induced recombination losses. Both scenarios impede the power conversion efficiency of solar cells. Therefore, it is essential to monitor the shadow, resistive, and metal-induced recombination losses associated with the design of front Ag contact. In this work, we demonstrate the application of photoluminescence (PL) imaging technique in association with the other conventional characterization techniques used in the optimization of front contact metallisation.

Thermally grown SiO2 is widely used for silicon surface passivation in solar cells and other applications due to excellent interfacial properties. SiO2 films with thickness in the range of 17 nm deposited by industrially viable spray-coating technique on both n- and p-type silicon are reported. Low values of interface state density of ${1.4}\times {10}^{{10}}$ cm $^{\boldsymbol -{2}}$ eV $^{\boldsymbol -{1}}$ on n-type and ${2.0}\times {10}^{{10}}$ cm $^{\boldsymbol -{2}}$ eV $^{\boldsymbol -{1}}$ on p-type were achieved. Fixed oxide charges in the range of 7.1– ${9.4}\times {10} ^{{11}}$ cm $^{\boldsymbol -{2}}$ and 3.9– ${6.5}\times {10} ^{{11}}$ cm $^{\boldsymbol -{2}}$ on n- and p-type, respectively, are obtained. Excellent passivation results in the effective surface recombination velocity of 0.97 cms $^{\boldsymbol -{1}}$ and 8.07 cms $^{\boldsymbol -{1}}$ at minority carrier concentration of $10^{{15}}$ cm $^{\boldsymbol -{3}}$ on n- and p-type Czochralski silicon, respectively, without the use of capping layer. SiO2 film exhibits dielectric breakdown field strength of 4.3 MVcm $^{\boldsymbol -{1}}$ and 5.6 MVcm $^{\boldsymbol -{1}}$ and leakage current density of ${2.2}\times 10 ^{\boldsymbol -{8}}$ Acm $^{\boldsymbol -{2}}$ and ${1.1}\times {10} ^{\boldsymbol -{8}}$ Acm $^{\boldsymbol -{2}}$ at 1 MVcm $^{\boldsymbol -{1}}$ on n- and p-type silicon, respectively. These values are superior to sol-gel-based SiO2 films reported previously and are comparable to or better than those reported for other methods for the growth or deposition of SiO2 on silicon. Amorphous nature of the film is validated by high-resolution transmission electron microscopy (TEM). The X-ray photoelectron spectroscopy (XPS) analysis shows nearly stoichiometric SiO x film.

We propose a parasitic BJT-based zero capacitor random access memory (Z-RAM) cell suitable for stand-alone memory applications. In this Z-RAM cell, high-bandgap TiO $$_2$$ is used as the source/drain material and silicon as the channel of an n-channel fully depleted silicon-on-insulator MOSFET. Using well-calibrated TCAD simulations, we demonstrate the programming of the proposed Z-RAM cell at low drain voltages, which is a major advantage from an application perspective. At low drain voltage, hole storage is initiated by band-to-band tunnelling, which is subsequently taken over by impact ionization. Large valence band offset between TiO $$_2$$ and Si ( $$\varDelta { E }_\mathrm{V }\approx$$ 2 eV) is utilized for storing larger number of excess holes inside the body for a longer time. This leads to the improvement of both sense margin and retention time compared to an all-silicon Z-RAM cell. We predict a retention time of 2 s and 70 ms at $$T=300$$ K and 358 K, respectively, for device gate length of 30 nm. We have optimized the device design to obtain a write ‘0’ time of 6 $$\upmu$$ s. Multiple non-destructive reading operation for the proposed Z-RAM cell is also demonstrated.

n-type and p-type silicon of various dopant concentrations (1014 to 1019 cm–3) are electrochemically characterized in a 1% hydrogen fluoride (HF) electrolyte with voltammetry, electrochemical imped...

Diamond-wire-sawing (DWS) technique allows slicing of silicon ingots to produce wafers at cheaper price due to its reduced kerf-loss and increased cutting rate. However, there is no cost-effective and industrially viable method available for texturing DWS wafers, especially for multicrystalline silicon (mc-Si) wafers. Currently additive-based acid texturing process is availed by PV manufacturing units for texturing DWS mc-Si wafers. An additive-free, low cost and energy-efficient acid texturing process is demonstrated for DWS mc-Si wafers in industrial production line. Nearly 10% absolute reduction in weighted average reflectance values (WAR) are noticed for the newly textured wafers from that of as-cut DWS mc-Si wafers and the WAR values are comparable to that of existing additive-based acid textured mc-Si wafers. An absolute reduction in emitter saturation current density by ~ 17 fA - cm - 2 and improved implied open circuit voltage of ~ 5 mV (absolute) are reported for lifetime sample fabricated using newly textured wafers when compared to the additive-based acid textured lifetime samples. An impressive batch average efficiencies of 18.20% and 18.24% are achieved for the additive-free and existing additive-based acid textured mc-Si cells, respectively. Detailed analysis conclude that ~ 1.5% (relative) enhancement in short circuit current density can be achieved by further process optimization. Cost analysis indicates that 60% of the chemical cost involved the texturing process can be cut down by replacing the existing additive-based acid process with the new method using the same process equipment. Hence, the texturing process presented has great potential for producing large area high efficiency mc-Si cells favoring cost considerations without compromising performance.

The analysis of performance degradation in photovoltaic (PV) modules with c-Si technologies as observed in the All-India Survey of PV Module Reliability 2018 is presented in this article. The degradation rates are correlated with the module age, system size, mounting configuration, and climate of deployment. Key failure modes responsible for the higher degradation rates seen in certain sites are identified using visual, infrared, and electroluminescence imaging. Potential-induced degradation is found to be the key mechanism responsible for higher degradation rates seen in Young sites. Also, deployment in hot climates and rooftops is seen to accelerate degradation. Multipoint analysis of degradation rates is presented at sites inspected in prior All-India Surveys.

We experimentally identified significant stressors that degrade the hydrophobic (contact angle > 90°) antisoiling coatings on exposure to Mumbai weather conditions, where losses due to dust deposition go up to 50% in three months. The contact angle of the antisoiling coatings changed from hydrophobic to hydrophilic (contact angle < 90°) in 12 weeks of field exposure. By testing the weakest performing coating on photovoltaic (PV) modules, no significant reduction of rate of dust deposition was observed on the coated PV module throughout the year. Soiling loss of the coated module went back to zero after every cleaning run (not seen in the uncoated module), which signifies ease of cleaning in the coated module. This resulted in a 2.2% lower soiling loss than the uncoated weekly cleaned module. This trend was reversed after four months of heavy rainfall, after which the uncoated module shows lower soiling loss than the coated module. Signatures of stressors identified by the field exposure test were: 1) rainfall—frequent natural cleaning during rain caused significant abrasion on the coated surface, and the acidic component of the rainfall reacted with the coating (which was verified by the indoor individual stress test), and 2) frequent manual cleaning runs, which lead to abrasion by dust and water (verified by the indoor individual stress test). The effect of frequent cleaning on the field was more severe, as, in real field condition, the combination of stressors acted concurrently. The effect of UV exposure and condensation was also studied by the indoor stress test, where the combination of UV exposure and condensation showed a statistically significant decrease in the contact angle (for all coatings). The rate of decrease in the contact angle was the highest for coating C, making it completely hydrophilic after 32 kWh/m2 of UV dose and 441 h of condensation. However, in indoor stress tests with individual stressors (UV exposure and water immersion), very high stress levels are required for producing a similar extent of degradation.

In this work, a nanosecond green laser (532 nm) is used to generate narrow openings by removing an ultra-thin (85 nm) SiN x layer that is coated on a silicon substrate for application in the fabrication of Passivated Emitter and Rear Contact (PERC) solar cells. An experimental analysis is presented to identify the optimal range of laser parameters for an efficient ablation with minimal damage to the silicon substrate. The ablated samples were characterized using a 3D profilometer to obtain the surface profiles and scanning electron microscope imaging to observe the surface quality. Further, energy-dispersive X-ray line analysis and atom probe tomography were performed to evaluate the nitrogen content on the surface and along the depth, respectively. The experimental results suggest that the SiN x layer starts to ablate only above a threshold laser fluence of 1.4 J/cm2, while the surface bulged out for laser fluence slightly below the ablation threshold. The central part of the ablated region was clean with a negligible nitrogen concentration at the surface, about ∼0.03% at a fluence of 2.4 J/cm2. Nitrogen concentration reduces continuously and almost becomes zero at 80 nm depth, suggesting complete ablation of the SiN x layer for establishing electrical contacts. The ablation width was close to the laser spot diameter only at lower values of the laser fluence. The lowest value of ablation depth was about 180 nm, suggesting that only about 95 nm layer of the silicon is ablated. The study demonstrates that nanosecond laser ablation is a potential technique for ablation of the SiN x layer of PERC solar cells but requires choosing the optimal parameters.

A photon-initiated chemical route for hydroxylation of CVD graphene and exfoliated graphene is presented. Hydroxyl functionalities have been bonded covalently to exfoliated and CVD graphene by treating the graphene with H2O2 in the presence of UV light. Back-gated graphene field effect transistors fabricated from hydroxyl functionalized graphene shows p-type doping and mobility in the range of 1000 cm2 V−1 s−1 which is much higher than reported in graphene oxide and reduced graphene oxide. Vacuum stability of hydroxyl functional groups is demonstrated by keeping hydroxyl functionalized graphene in vacuum for 22 h and comparing the electrical characteristics. As a further proof of –OH functionalization, we demonstrate the deposition of Al2O3 by atomic layer deposition, which is not possible on pristine graphene.

A simple yet reproducible method to deposit high quality aluminium oxide (AlOx) film by spray coating is presented. Excellent thickness and refractive index uniformity is demonstrated. The AlOx film was found to be nearly stoichiometric with an oxygen to aluminium ratio of 1.7 from X-ray photoelectron spectroscopy (XPS) measurements. An interfacial layer with thickness of about 2 nm was observed in transmission electron microscopy analysis. The interfacial layer was determined to be aluminium silicate from XPS data. Electrical characterization of the films on Czochralski (Cz) p-type silicon yielded dielectric constant of 6.5 and mean breakdown field of 4.7 MV cm−1. Interface state density of 8.7 × 10 10 eV−1cm−2 and fixed charge density of − 5.5 × 10 12 cm−2 were obtained from the electrical characterization of metal insulator semiconductor capacitors. The excellent interface quality with low interface state density and high negative charge is suitable for passivation of p-type silicon in solar cell applications. Effective surface recombination velocity of 12 cm s−1 and 48 cm s−1 were obtained for Cz p-type silicon surface for annealing temperature of 750°C and 790°C respectively without the use of capping layer.

The fundamental building block of an artificial spiking neural network (SNN) is an element which can effectively mimic a biological neuron. There are several electronic and spintronic devices which have been demonstrated as a neuron. But the main concern here is the energy consumption and large area of those artificial neurons. In this letter, we propose and demonstrate a highly scalable and CMOS compatible bulk FinFET with an ${n}^{+}$ buried layer for ultra low energy artificial neuron using well calibrated TCAD simulations. The proposed device shows the signature spiking frequency versus input voltage curve of a biological neuron. The energy per spike of the integrate block of the proposed leaky integrate and fire (LIF) neuron is ${6.3}~\textit {fJ}$ /spike which is the minimum reported till date.

Texturing of diamond wire sawn (DWS) monocrystalline silicon (c-Si) wafers by alkaline process is well established. However, texturing of multicrystalline silicon wafers (mc-Si) is discerned to be a concern. All the DWS mc-Si texturing schemes reported so far either use additives or require additional processing steps which entail additional monetary investment. An additive-free, cost-effective, non-metallic, energy efficient acid based texturing scheme is demonstrated here for the DWS mc-Si wafers. The proposed novel texturing technique recommends hydrofluoric (HF) acid rich acidic solution for obtaining uniform porous silicon (Por-Si) layer, followed by a dilute alkaline dip to obtain a porous inverted rounded structures on the DWS mc-Si wafer surface. The percentage of HF volume in acid texturing solution was varied from 40% to 60% in achieving the best minority carrier lifetime of ∼90 μ s in our optimized recipe, therefore suitable for industrial texturing process. The weighted average reflectance (WAR) of our textured mc-Si wafers are ∼29.0% and ∼6.5% after texturing and after final anti-reflective coating, respectively. The cells fabricated using the new acid texturing scheme exhibited an excellent batch average efficiency of 18.46% in industry environment. In the present study, DWS textured wafers are characterized for optoelectronic properties like total reflectance and Photoluminescence (PL) imaging on full wafer area and benchmarked in detail against standard acid textured multi-wire slurry sawn (MWSS) mc-Si wafers, and promising results are reported. A detailed methodology to understand the chemical process of texturing mc-Si wafers using HF-rich acid chemistry is discussed. The reported HF-rich acid texturing process can be easily implemented in any industrial acid texturing tool without any additional investment.

In this paper, we have developed a physics-based analytical model for the electrical characteristics of passivated silicon carrier-selective contact (CSC) solar cells and validated it with numerical simulations. The model comprises analytical solutions of: 1) the Poisson equation, accurately capturing the level of inversion and accumulation at the crystalline silicon (c-Si) layer interfaces, and 2) the recombination current capturing the various recombination mechanisms at work in the solar cell. The calculations establish that CSC solar cells have the potential to achieve an efficiency greater than 26% even when both c-Si interfaces have realistic SRV values of 100 cm/s. The model helps illustrate the physics underlying the performance of CSC solar cells for variation in key device parameters such as surface recombination velocities, bulk lifetime, contact layer doping, and amorphous silicon (a-Si) thickness amongst others. By circumventing the need for resource-intensive numerical simulations, the analytical model described in this paper can assist in the design and development of high-performance CSC solar cells.

The natural soiling of photovoltaic cover glass has recently been shown to include both an inorganic and organic particulate matter. Under favorable growth conditions, the latter can lead to the growth of dense colonies of filamentous fungi, which potentially leads to measurable performance losses over time. Herein, we report on a field study where glass coupon samples were deployed in soiling-prone locations, which focused on Dubai (United Arab Emirates) and Mumbai (India). For each site location, clear differences in the soiling were observed. The samples from Mumbai were contaminated with an abundance of filamentous fungi, whereas the samples from Dubai had primarily inorganic contamination. The effectiveness of soiling mitigation strategies, which include cleaning techniques and glass coatings, are discussed in detail.

We experimentally explored vertical mounting of bifacial modules of different bifacialities for mitigating soiling in Mumbai, where the dust accumulation rate in terms of energy loss per day can be as much as 0.45%. Bifaciality is commonly referred to the ratio of the back side value to the front side value of any of the performance parameters I sc, P max, or ῃ. The energy loss due to soiling in vertically mounted bifacial modules and monofacial and bifacial modules mounted at the latitude angle are compared. The experiments reveal that the vertically mounted bifacial modules have nearly zero soiling loss; bifacial modules mounted at latitude angle with 90% bifaciality have lower soiling rate; the energy yield of vertically mounted bifacial modules with 90% bifaciality can exceed that of bifacial modules mounted at latitude angle after three weeks if the modules are left to soil without cleaning; the peak temperature of operation of vertically mounted bifacial modules is seen to be 15 °C lower than that of bifacial modules mounted at latitude angle, implying potential benefits in long-term reliability and performance ratio; combining vertically mounted bifacial modules and bifacial modules mounted at latitude angle, a nearly flat, extended generation profile can be obtained.

This paper presents the study of the effect of mechanical loading cycle parameters on the crack generation and power loss for two different types of interconnect designs. Mechanical loading at a lower pressure has been found to cause cracks in the cell, whereas higher pressure causes cell cracks along with interconnect breakages. It has been found that there is saturation in the power loss and cell cracks after a certain number of cycles. Lower frequency (slow) DML requires more number of DML cycles to create same level of cracks as compared to high frequency (fast) DML. This helps us to identify an accelerated test protocol for dynamic mechanical loading.

As solar deployment world-wide prepares to accelerate after the pandemic, many regions and countries will attempt to build up a sustainable solar manufacturing ecosystem. The reasons for this may be manifold – energy security, job creation, investment in new green technologies, and potential reduction in costs. Questions which arise are whether the full value chain of manufacturing should be taken up, and what are the types of technology to be used. This paper addresses these points, and proposes possible policy and technology paths to be followed for India. It also suggests how lessons being learned in India in solar manufacturing could be applied globally.

Cleaning solar PV panels’ surface is a standard method for mitigating soiling-related losses. The cleaning process may result in the abrasion of any coatings on the surface of the glass. We have developed a cleaning cycle simulator to emulate the various stressors that influence abrasion during cleaning events in the field. Using this simulator, we investigated the effect of abrasion caused by two different types of brush designs (linear and rotary cleaning brushes) used in robotic cleaning on coated (with anti-soiling coatings) and not-coated solar glass samples. Coated samples (A, B, C and D) that went through linear abrasion cycles showed higher degradation than rotary abrasion. This is shown to be due to the higher weight applied by the linear brush on the surface of the sample compared to the rotary brush bristles. The not-coated sample shows an increase in contact angle and roughness after 3700 linear and rotary abrasion cycles. This is demonstrated by XPS analysis to be due to the deposition of nylon on the glass during cleaning. The brush bristles' tips show significant damage to its shape after linear and rotary abrasion. Bristle diameter of the linear brush bristle decreased significantly after 3700 cycles of linear abrasion. The hardness of the brush bristles’ tips showed a significant decrease after undergoing 3700 abrasion cycles, with more severe damage in the case of linear abrasion. Brush designs may have to be accordingly modified to account for these observations.

We demonstrate a method to dope monolayer chemical vapor deposited (CVD) graphene with nitrogen and make it ferromagnetic. CVD graphene was first functionalized with hydroxyl groups by treating with H2O2 in the presence of UV light and then annealed in ammonia gas to dope it with nitrogen. Magnetization measurements showed a ferromagnetic hysteresis loop at low temperatures with a coercivity of 222 Oe at 2 K. We also investigated the effect of a change in the angle of the applied magnetic field on the anisotropic magnetoresistance effect (AMR) in the doped CVD graphene devices. Graphene shows positive AMR for temperatures from 2 K to 50 K, negative AMR at 100 K and 150 K, and no AMR for temperatures higher than 150 K. A maximum AMR of 0.92% was observed at 2 K for an in-plane magnetic field of 30 kOe. Magnetic force microscopy also confirms the introduction of magnetism in CVD graphene after doping, and electron spin resonance spectroscopy shows resonance when scanned in a magnetic field, which confirms the presence of unpaired electrons in doped graphene. The process introduced in this paper for nitrogen doping of graphene with attendant magnetism could pave the way for the applications of graphene in spintronics and other devices.

We report a technical survey of the Solar Pump Irrigators Cooperative Enterprise (SPICE), which started operation in May 2016. Survey mostly followed the methodology developed as part of the All India Survey of PV Module Reliability. High rates of PV module performance degradation, high rate of soiling, and instances of PV panel shadowing due to overgrowth of crop are observed. Leveraging the scale brought in by the cooperative model for addressing the technical issues, by better negotiations for quality hardware, and training of farmers for better operation and maintenance of the PV systems could improve the economic yield of the agrophotovoltaic experiments like SPICE.

Simulation models for I-V characteristics of PV modules under mismatch conditions often assume ideal bypass diode and ignore the reverse leakage current of cells. In this paper, we present a SPICE based model in which customized reverse leakage current and real I-V characteristics of bypass diodes can be specified. This model is used to gain insight into root causes of some of the unusual I-V characteristics seen in field deployed modules. Different mismatch scenarios for a PV module were simulated for both the modules made up of leaky and non-leaky cells, and the resultant I-V curves were compared. The effect of Potential Induced Degradation (PID) on the I-V curves of PV modules was also simulated under the presence of mismatch. Using this model, we accurately reproduced the I-V characteristics of fielded modules degraded due to PID, and Bypass Diode failure in the short circuit condition.

Low cost metal assisted chemical etching (MACE) based black silicon (b-Si) texturization process is demonstrated for diamond wire sawn (DWS) multi-crystalline (mc-Si) wafers. Acid etching followed by diluted alkaline solution based polishing processes are used for modifying the b-Si surface for suppressing the heavy recombination associated with b-Si surfaces. Surface modification of b-Si results in random inverted pyramid textures with balanced optical and electrical properties. Correlation between surface morphology and its opto-electronic properties are investigated in detail. Low weighted average reflectance of 16.8% (without ARC) and minority carrier lifetime of $72\ \mu\mathrm{s}$ is reported for optimized b-Si modified textured mc-Si wafers.

Energy loss due to soiling of photovoltaic modules is one of the most reported problems in sunbelt countries. Anti-soiling coatings (ASC) which reduces soiling, offers an economical and universal solution. Since ASC is applied on the outer surface of the PV module, durability of these coatings is essential. In this paper, we compared the field degradation rates of 4 different (named A, B, C and D) commercial hydrophobic ASC in Mumbai, India (warm and humid climate). The degradation rate of ASC was determined in terms of reduction of contact angle per day. Contact angle of one of the ASC changed from hydrophobic to hydrophilic in 5 days of field exposure and all other coatings became hydrophilic in 40 days of field exposure during rainy season. Degradation rates of ASC during rainy season was more than 4 times than that of non-rainy season for all coated samples. Accelerated laboratory tests using acidic water (pH 6) showed good correlation with field exposure for coatings A and C. Laboratory studies on the mechanical impact of rain showed linear rates of degradation for all coated samples, which correlated well with the field exposure study during rainy season. This indicates that the mechanical impact of rain, in addition to the pH and UV exposure reported earlier, as a significant stressor for ASC.

ASTM D4169, the main reference for vibration profiles in IEC62759-1:2015 recommends to simulate only the vertical vibration for evaluation of the robustness of PV modules to transportation. This study focusses on the lateral vibrations measured in vertically placed modules. Acceleration data was collected from the transportation of 2 standard pallets of 25 PV modules. It is found that the lateral vibrations at around 15 Hz is severe and sometimes it is higher than the vertical vibration test profile recommended by ASTM D4169. The modules placed front side facing front side showed lesser vibrations compared to the modules placed front side facing backside. Also, the module placed at the middle of the pallet is found to have lesser lateral vibrations.

Dust deposition on photovoltaic module can reduce energy generation up to 50% if not cleaned for 4 months in Mumbai, India (warm and humid climate). Hydrophobic (contact angle> 90°) anti-soiling coating (ASC) is a cost-effective mitigation strategy to reduce soiling. In this paper, we compared the cleaning efficacy of 4 different commercial hydrophobic anti-soiling coatings (on solar glass and PV modules) with a not-coated sample. All coated glass samples (A, B, C and D) showed higher cleaning efficacy (lower soiling loss) than the not-coated glass sample after cleaning with a 45 µl deionized water droplet. This was also confirmed by field exposure study done on PV modules (for coating B,C and D). Cleaning efficacy of the coating D (on PV module) decreased significantly after 2nd manual cleaning run, indicating abrasion caused by the cleaning tool, implying that the selection of cleaning methods/tools is critical. Under controlled environment (on solar glass) cleaning efficacy of all coated glass samples reduced by a factor of 6 (average) as the rolling water droplet travels from top to bottom, covering a total distance of 3.6 cm, This is due to the reduction in speed of the water droplet rolling off the surface as it accumulates more dust. Roll of angle for clean coated glass increases by a factor of 2 (for coating A,C and D) when measured on dust deposited glass substrate, indicating that roll-off angle depends on the surface of the ASC coatings, which may vary with exposure time and environmental conditions like soiling rate. Ranking of cleaning efficacy of ASC under field exposure correlated well with the roll-off angle measured on soiled samples in controlled experiments. This suggest roll - off angle as an important measure for the evaluation of the anti-soiling coatings.

An industrially viable spray-coating technique is demonstrated for silicon dioxide (SiO 2 ) thin film deposition to passivate n-type silicon surface. SiO 2 films of ~10 nm thickness are deposited. XPS analysis reveals nearly stoichiometric film. An effective surface recombination velocity (S eff ) of 8 cm sec−1 and 6 cm sec−1 is achieved on n-type Czochralski silicon after aluminum anneal (alneal) and forming gas annealing (FGA) processes, respectively without any capping layer. Low S eff values are explained using interface state density (D it ) and fixed oxide charge density (Qf) extracted from conductance-voltage and capacitance-voltage characteristics of fabricated metal-oxide-semiconductor capacitors. In case of FGA, field-effect passivation is dominant, whereas chemical passivation is dominant in case of alneal.

In this paper, we have proposed a deep learning network for classification of electroluminescence (EL) image of solar cells into good or cracked cells for low resolution images captured in the field. Such crack detection in EL images is becoming important to reduce the time required for manual inspection and to minimize human error. Most implemented deep learning methods use high-resolution images captured in controlled environment inside a lab for training the network model. This model, when used for field data will not perform well due to non-ideal conditions. In our work we use, EL images collected from PV power plants located in different parts of India during ‘All India Survey 2018’, which include 5 climatic zones and modules from 20 different module manufacturers to train the deep neural network. The EL images were captured using a customized CMOS-based camera having comparatively lower resolution. Thus the deep neural network model is trained for on field variations and the accuracy of crack detection is 98.59% even for the lower resolution.

In this paper, role of cloud movement in generation of spurious data in PV power plant SCADA systems has been described. Significant deviation from linear relationship between SCADA recorded current vs irradiance in a multi-megawatt PV power plant, which has only one weather station recording the irradiance, is seen in many instances. Such deviations were shown to be the attribution of cloud movements causing varying shading on different blocks of modules connected to different string monitoring boxes (SMBs) and the pyranometer. Such issues leading to spurious signals in SCADA records can be minimized by having more number of pyranometers spread across the plant or by detecting and eliminated these spurious signals from analvsis by looking at the time-series data.