Rear Contact Research Articles

Recycling of Photovoltaic Modules – A Strategy for Silicon and Metal Contact Recovery

As the installed capacity of photovoltaic (PV) systems continues to grow, also does the necessity to address the accumulating waste from decommissioned PV modules. Millions of modules will need to be retired in the next few decades, and this poses a challenge that requires the development of cost-effective and efficient recycling strategies, with a focus on essential components such as solar cells, which are known for their significant environmental impact and energy budget. This study explores strategies to recover metal from front and rear contacts, as well as the potentiality of silicon substrate recrystallization. Alkaline-organic solutions allow for complete metal detachment with small-to-minimal silicon loss, and recrystallization of recovered substrates provides promising results in obtaining wafers suitable for the newly established industry requirements. Al-BSF solar cells fabricated from recycled materials exhibit improved performance, proving the feasibility of reclaiming precious metals and silicon substrates from PV modules. These encouraging first results represent an important step towards cycling PV systems within a circular economy framework, thereby minimizing waste and maximizing resource utilization.

Effect of Iron Contamination and Polysilicon Gettering on the Performance of Polysilicon‐Based Passivating Contact Solar Cells

ABSTRACTOver the past decade, silicon solar cells with carrier‐selective passivating contacts based on polysilicon capping an ultra‐thin silicon oxide (commonly known as TOPCon or POLO) have demonstrated promising efficiency potentials and are regarded as an evolutionary upgrade to the PERC (passivated emitter and rear contact) cells in manufacturing. The polysilicon‐based passivating contacts also exhibit excellent gettering effects that relax the wafer and cleanroom requirements to some extent. In this work, we experimentally explore the impact of bulk iron contamination and polysilicon gettering on the passivation quality of the polysilicon/oxide structure and the resulting solar cells performance. Results show that both n‐ and p‐type polysilicon/oxide passivating contacts are not affected by iron gettering, demonstrating robust and stable passivation quality. However, for a very high bulk iron contamination (1 × 1013 cm−3), the accumulated iron in the p‐type lightly boron‐doped emitter in crystalline silicon would degrade the emitter saturation current density. This can cause a reduction in both open‐circuit voltage and short‐circuit current. Meanwhile, this very high iron content (1 × 1013 cm−3) can further degrade the fill factor and temperature coefficient of the cells. On the other hand, for an initial iron content of 2 × 1012 cm−3, which should be well above the iron level in the current industrial Czochralski silicon wafers, the resulting cells demonstrate similar performance as the control group with no intentional iron contamination. This work brings attention to both the benefits of polysilicon gettering effects as well as the potential degradation due to the accumulation of metal impurities in the p‐type emitter region.

Enhancing kesterite-based thin-film solar cells: A dual-strategy approach utilizing SnS back surface field and eco-friendly ZnSe electron transport layer

The development of kesterite-based thin-film solar cells (TFSCs) has faced significant challenges, particularly due to unstable rear contact properties and low power conversion efficiency (PCE). Despite various individual approaches aimed at addressing these issues, progress has remained limited. In this study, a dual strategy is explored to address these problems simultaneously. First, the impact of an SnS intermediate layer at the back surface field in conjunction with an FTO back contact is examined. Second, the introduction of a stable PN Mott-Schottky junction is assessed by utilizing an eco-friendly ZnSe electron transport layer (ETL) as a replacement for the conventional, yet toxic, CdS ETL. The combined application of these strategies produces a synergistic effect, leading to significant improvements in the solar cell’s microstructure and key electrical parameters, including open-circuit voltage (VOC), short-circuit current density (JSC), and overall PCE. Additionally, this approach mitigates band-tailing states and reduces deep-level defects often associated with the annealing process. As a result, the power conversion efficiency is significantly enhanced, rising from 1.31 ± 0.13 % to 7.68 ± 0.98 %. This effective dual-strategy offers new insights into overcoming the challenges of unstable rear contact properties and suboptimal device parameters, paving the way for further advancements in the performance of kesterite-based TFSCs.

UV‐Induced Degradation of Industrial PERC, TOPCon, and HJT Solar Cells: The Next Big Reliability Challenge?

With the surge of UV‐transparent module encapsulants in the photovoltaic industry aiming to boost quantum efficiency, modern silicon solar cells must now inherently withstand UV exposure. UV‐induced degradation (UVID) of nonencapsulated laboratory and industrial solar cells from several manufacturers is investigated. Passivated emitter rear contact (PERC), tunnel oxide passivating contact (TOPCon), and silicon heterojunction (HJT) cells can suffer from severe implied voltage degradation (>20 mV) after UV exposure relating to 3.8 years of module installation in the Negev desert. Front UV‐exposure causes more performance loss than an equal rear dose. This is connected to a higher UV transmission of the cell layers outside the bulk, indicating the photons need to reach the silicon surface to induce damage. Current–voltage measurements of the TOPCon groups most sensitive to UV degradation show more than 7%rel efficiency loss with the Voc as the main contributor. For two TOPCon groups, dark storage for 14 days after UV exposure causes an additional voltage drop on a similar scale as the UV damage itself, impeding straightforward reliability testing. UVID appears to be a complex process general to all dominant cell architectures with the potential to diminish efforts in efficiency optimization within only a few years of field employment.

A comparative numerical simulation study of CIGS solar cells with distinct back surface field layers for enhanced performance

The objective of this study is to explore the impact of various back surface field (BSF) layers including copper aluminium oxide (CuAlO2), Copper Antimony Sulphide (CuSbS2), Formamidinium tin triiodide (FASnI3), poly (3-hexylthiophene) P3HT to boost the output of conventional baseline CIGS solar cells structured. The device performance increases because of the minimized surface recombination velocity through heavily doped BSF layers, which increases the electric field at the rear contact. Among all proposed BSF layers CuAlO2 gives the best photoconversion efficiency (η) of 24.61 % followed by fill factor (FF) of 83.11 %, short circuit current density (JSC) of 35.87 mA/cm2, and open circuit voltage (VOC) of 0.82 V with quantum efficiency (QE) of ∼92 % for the whole visible range with the onset happening at ∼ 560 nm, thanks to the enhancement of carrier collection when BSF layer is incorporated. The novelty in this work is that for the first time with the CuAlO2 BSF layer, 24.61 % efficiency is reported at 1 μm CIGS layer thickness. We also examined how different BSFs affect the PV performance of the devices. The effect of temperature, the doping concentration of the BSFs, varying gallium proportion, JV & QE analysis, band diagram, and radiative recombination coefficient are varied to observe their impact on the PV parameters. This research introduces novel CIGS/CdS heterojunction configurations using various BSF layers to enhance efficiency, supporting the advancement of ultrathin, flexible, and tandem solar cell applications.

Validation of a phase-field approach for contact line hysteresis against a sloshing droplet case

AbstractUnderstanding liquid propellants behavior in microgravity conditions is critical for efficient spacecraft design. For a number of operations, ranging from engine restart to orbital propellant storage and transfer, insight is needed to characterize capillary-dominated flows. In such conditions, surface tension and wetting properties, including contact angle hysteresis, can greatly impact the fluid’s behavior and therefore spacecraft performance. Using experimental data from ESA Propulsion Laboratory, a contact line model for the Cahn–Hilliard phase-field method is validated. The case studied is that of a droplet confined between two oscillating plates, which aims to isolate and observe contact angle-driven physics, limiting the effect of gravity on the flow in a simple and reproducible way on ground. The contact line model allows for the prediction of contact line motion without requiring the computation of dynamic contact angles or contact line velocities, thus simplifying implementation and reducing computational overhead. For the validation, contact line pinning and motion under varying oscillation frequencies is investigated. Specifically, the length between the rear and front contact line edges, as well as the shape of the sloshing droplet are compared. The results show good agreement between simulations and experimental data, confirming the model’s accuracy in predicting contact line behavior and pinning.

Optimization of Sr3NCl3-based perovskite solar cell performance through the comparison of different electron and hole transport layers

Strontium Nitride Trichloride (Sr3NCl3) is a promising absorber material for solar cells due to its unique structural, electrical, and optical properties. We conducted a thorough investigation to scrutinize the structural, optical, and electronic characteristics and the photovoltaic efficiency of double-heterojunction solar cells utilizing Sr3NCl3 absorbers. Various metals were evaluated for the front and rear contacts to determine the optimal metal-semiconductor interface, with the study determining that silver (Ag) is the most suitable option for the front contact and nickel (Ni) for the back contact. The PV performance of innovative Sr3NCl3 absorber-based cell structures was evaluated with two different Hole Transport Layers (HTLs), MASnBe3 and CBTS, alongside ZnO and WS2 serving as the transition metal dichalcogenide (TMD) Electron Transport Layers (ETLs). This investigation examined a range of factors, such as layer thickness, operational temperature, doping density, defect densities at both the interfaces and within the bulk, carrier generation and recombination rates, quantum efficiency (QE), series versus shunt resistance, absorption coefficient, and current density-voltage (J-V) characteristics, utilizing the SCAPS-1D simulator software. Fine-tuning of both two HTL and ETL revealed that the highest power conversion efficiency (PCE) of 27.34 % with JSC of 19.78 mA/cm2, fill factor (FF) of 88.84 %, and VOC of 1.56 V was achieved with MASnBe3 HTL and ZnO ETL, while the lowest PCE of 25.55 %, with JSC of 19.77 mA/cm2, FF of 89.07 %, and VOC of 1.45 V was obtained for CBTS HTL and WS2 ETL, respectively. These findings highlight the promising potential of Sr3NCl3 absorbers with ZnO as ETL and MASnBe3 as HTL for developing advanced perovskites heterostructure solar cells for enhanced performance in the future.

Universal droplet propulsion by dynamic surface-charge wetting

Controllable droplet propulsion on solid surfaces plays a crucial role in various technologies. Many actuating methods have been developed; however, there are still some limitations in terms of the introduction of additives, the versatilities of solid surfaces, and the speed of transportation. Herein, we have demonstrated a universal droplet propulsion method based on dynamic surface-charge wetting by depositing oscillating and opposite surface charges on dielectric films with unmodified surfaces. Dynamic surface-charge wetting propels droplets by continuously inducing smaller front contact angles than rear contact angles. This innovative imbalance is built by alternately storing and spreading opposite charges on dielectric films, which results in remarkable electrostatic forces under large gradients and electric fields. The method exhibits excellent droplet manipulation performance characteristics, including high speed (~130 mm/s), high adaptability of droplet volume (1 μL–1 mL), strong handling ability on non-slippery surfaces with large contact angle hysteresis (CAH) (maximum angle of 35°), significant programmability and reconfigurability, and low mass loss. The great application potential of this method has been effectively demonstrated in programmable microreactions, defogging without gravity assistance, and surface cleaning of photovoltaic panels using condensed droplets.

Enhancing Reliability and Regeneration of Single Passivated Emitter Rear Contact Solar Cell Modules through Alternating Current Power Application to Mitigate Light and Elevated Temperature‐Induced Degradation

The study explores a novel method to combat the Light and Elevated Temperature‐Induced Degradation (LeTID) in solar cell modules, which significantly reduces their efficiency and lifespan. This method involves applying alternating current (AC) of various waveforms (triangular, sinusoidal, and square) and frequencies (5 and 100 kHz) to boron‐doped p‐type passivated emitter rear contact (p‐PERC) solar cell modules. This approach effectively lowers the series resistance at the critical junction between the silver (Ag) contact and the silicon emitter layer of the PERC solar cell, thereby reducing charge recombination hindered by high resistance, especially at elevated temperatures. As a result, there is an improved flow of electrical charges, leading to decreased energy loss and increased solar cell efficiency. The study's findings indicate that a slow, smooth sinusoidal AC waveform at 100 kHz is particularly effective, restoring about 100% of the original performance of the panel. Moreover, oscillations at 5 kHz also show considerable efficacy, recovering more than 96% of the performance. The sinusoidal waveform is noted to surpass both triangular and square waveforms in recovery efficiency. This research highlights the use of high‐frequency AC electricity as a viable strategy to extend the lifespan and enhance the performance of solar panels.

Characterization of rear-side potential-induced degradation in bifacial p-PERC solar modules

Bifacial solar modules are increasingly preferred over monofacial modules to maximize the solar power output within a limited space. Owing to their high efficiency and compatibility with existing production lines, bifacial p-type passivated emitter and rear contact (p-PERC) solar modules have dominated the market since their commercialization. This study analyzes the influence of Al2O3, a passivation layer of p-PERC solar cells, on the PID and its underlying mechanism. Experiments were conducted on bifacial p-PERC module samples to analyze their electrical properties. Additionally, cell-like samples were fabricated to measure characteristics, for example, carrier lifetime, that are difficult to assess in full modules. To accelerate module degradation, experiments were conducted at 85 °C and 85 % humidity, while a voltage of −1000 V was applied to investigate the PID phenomenon. The results reveal degradation at the rear of the module caused by polarization effects, which were confirmed through changes in solar cell parameters and recombination current. The proposed mechanism indicates that the degradation in bifacial p-PERC solar modules is caused by the field-effect deterioration of the Al₂O₃ layer caused by alkali ions diffusing from the glass. This is observed through changes in the carrier concentration within Si and the detection of alkali ions within Al2O3. Our analysis considers both module and cell structure samples to delineate the influence of Al2O3 on the PID, which has not been previously reported. This study enhances the understanding of the polarization effect in bifacial p-PERC solar cells, thus contributing to the advancement of solar cell passivation strategies.

Tantalum doped tin oxide enabled indium-free silicon heterojunction solar cells with efficiency over 25 %

Reducing indium consumption has received increasing attention in contact schemes of high efficiency silicon heterojunction (SHJ) solar cells. It is imperative to discover suitable, low-cost, and resource-abundant transparent electrodes to replace the conventional, resource-scarce indium-based transparent electrodes. Herein, tantalum doped tin oxide (TTO), prepared through low-temperature sputtering, is selected as an alternative material. Notably, the Anti-Burstein-Moss effect of TTO is observed, which is ascribed to variations of stress in films. Based on this finding, TTO was first applied to SHJ solar cells, and the photoelectric tradeoff in front and rear contacts is gained by matching nanocrystalline silicon layers and adjusting TTO thickness. Ultimately, an indium-free SHJ solar cell with an efficiency of 25.15 % is obtained (certified efficiency 25.10 %, 274.30 cm2).

Solar Cells on Multicrystalline Silicon Thin Films Converted from Low‐Cost Soda‐Lime Glass

AbstractFabrication and characterization of solar cells based on multicrystalline silicon (mc‐Si) thin films are described and synthesized from low‐cost soda‐lime glass (SLG). The aluminothermic redox reaction of the silicon oxide in SLG during low‐temperature annealing at 600 – 650 °C leads to an mc‐Si thin film with large grains of lateral dimensions in the millimeter range, and moderate p‐type conductivity with an average Al acceptor concentration between 5 × 1016 and 1.2 × 1017 cm−3 in the bulk. A residual composite layer of mainly alumina and unreacted Al forms beneath the mc‐Si thin film as the second product of the crystalline silicon synthesis (CSS) process, which can be used as rear contact in a vertical solar cell design. The mc‐Si absorber (≈10 µm) is thin enough that the diffusion length given by a minority carrier lifetime of ≈1 µs exceeds the path length to the top contact several times. Homojunction and heterojunction diodes have been fabricated on the mc‐Si thin films and show great potential of CSS for the realization of high‐performance solar cells.

Electrical Performance, Loss Analysis, and Efficiency Potential of Industrial‐Type PERC, TOPCon, and SHJ Solar Cells: A Comparative Study

ABSTRACTCurrently, the efficiency of p‐type passivated emitter and rear contact (PERC) cells has been growing at an absolute efficiency of 0.5% per year and has reached 23%–23.5% in mass production while getting closer to its theoretical efficiency limit. n‐Type tunnel oxide passivated contact (TOPCon) and silicon heterojunction (SHJ) cells with their superior “passivating selective contacts” technology were the most interesting photovoltaics (PV) technology in the industry. The effect of different passivated contact layers with respect to their influence on the J0, J0,metal, ρc, and the carrier selectivity (S10) and the loss analysis and efficiency potential of industrial‐type PERC, TOPCon, and SHJ solar cells were studied and compared. The results showed that TOPCon structure with a high passivation performance and good optical performance is more suitable for bifacial solar cell and the highest theoretical limiting efficiency with metal shading on the n‐type Si wafer (ηb,e,h,m,max) can be achieved to 27.62%. Although SHJ structure with the highest passivation performance but the worst optical performance owing to the parasitic absorption of a‐Si:H layer and high contact resistivity, the value of ηb,e,h,m,max is 0.7% lower than that of TOPCon solar cells. PERC structure has superior optical performance than SHJ structure, but due to poor passivation performance, the ηb,e,h,m,max is only 26.42%. The next‐generation products may be heterojunction back‐contact (HBC) and TOPCon back‐contact (TBC) cells with high ηb,e,h,m,max of 28.12% and 27.99%, respectively. Exploiting a perfect passivation of the noncontact area, the wide process window and low cost are required and transferring these new concepts to industrial solar cell production will be the next major challenge.

Drive-By Identification of Joint Bridge Damage and Surface Roughness Based on Sensitivity Analysis of Residual Contact Point Deflections

Drive-by inspection of bridge damage using a passing vehicle’s dynamic response has great potential in bridge damage identification. Among the current drive-by methodologies, the methods based on bridge modeling have been proposed for the quantitative identification of bridge damage and bridge surface roughness. However, the coupling of bridge damage and unknown surface roughness increases the difficulty of the identification problem and most previous studies conduct the identification task of bridge damage or bridge surface roughness separately. In this paper, a novel method is proposed for the identification of joint bridge damage and bridge surface roughness based on the residual bridge deflections from the front and rear wheels contact points of an instrumented passing vehicle. The vehicle–bridge interaction is analyzed using a half-car model of a four degrees of freedom (4-DOF) with front and rear vehicle wheels. First, the vehicle–bridge unknown forces and displacement of the vehicle axles are identified by the generalized Kalman filter under unknown input (GKF-UI) proposed by the authors. The sensors can be installed conveniently on the vehicle body due to GKF-UI. Then, the residual bridge deflections from the front and rear vehicle wheels contact points are utilized to eliminate the effect of road surface roughness. Afterward, bridge structural damage is identified based on the sensitivity analysis of residual bridge deflections from the front and rear contact points with [Formula: see text]1-norm regularization. Finally, bridge road surface roughness is estimated based on the identified unknown forces and updated bridge model with damage. The results of numerical identification examples demonstrate the effectiveness of the proposed method for the identification of joint bridge damage and surface roughness.

Exploratory analysis of injury severity under different levels of driving automation (SAE Levels 2 and 4) using multi-source data

Vehicles equipped with automated driving capabilities have shown potential to improve safety and operations. Advanced driver assistance systems (ADAS) and automated driving systems (ADS) have been widely developed to support vehicular automation. Although the studies on the injury severity outcomes that involve automated vehicles are ongoing, there is limited research investigating the difference between injury severity outcomes for the ADAS and ADS equipped vehicles. To ensure a comprehensive analysis, a multi-source dataset that includes 1,001 ADAS crashes (SAE Level 2 vehicles) and 548 ADS crashes (SAE Level 4 vehicles) is used. Two random parameters multinomial logit models with heterogeneity in the means of random parameters are considered to gain a better understanding of the variables impacting the crash injury severity outcomes for the ADAS (SAE Level 2) and ADS (SAE Level 4) vehicles. It was found that while 67 percent of crashes involving the ADAS equipped vehicles in the dataset took place on a highway, 94 percent of crashes involving ADS took place in more urban settings. The model estimation results also reveal that the weather indicator, driver type indicator, differences in the system sophistication that are captured by both manufacture year and high/low mileage as well as rear and front contact indicators all play a role in the crash injury severity outcomes. The results offer an exploratory assessment of safety performance of the ADAS and ADS equipped vehicles using the real-world data and can be used by the manufacturers and other stakeholders to dictate the direction of their deployment and usage.

Inorganic charge transport layer for efficient Pb-free KSnI3 based perovskite solar cells: a theoretical study

The power conversion efficiency (PCE) of lead (Pb)-based perovskite solar cells (PSCs) is remarkably high; however, the toxicity of Pb poses a significant barrier to their commercial viability. In the current study, the effect of different charge transport layer (CTL) materials on the performance of the Pb free Sn-based (KSnI3) PSCs has been studied by using SCAPS simulations. Tin oxide (SnO2), zinc oxide, and titanium dioxide as electron transport materials, whereas spiro-OMeTAD, copper oxide (Cu2O), and nickel oxide as hole transport layer materials were iterated to achieve the optimum photovoltaic parameters. The photovoltaic parameters were optimized in terms of the active layer and CTL thicknesses, as well as the doping concentration, defect density, and interfacial defect density. Moreover, the impact of series and shunt resistance on the performance of PSCs is also investigated. The most efficient PSC with PCE of 21.75% was achieved with the device structure of FTO/SnO2/KSnI3/Cu2O. This efficiency is higher than previously reported KSnI3 based-PSCs. The SnO2 (ETL) and Cu2O were proven to be most efficient choices for the CTL materials. It was also observed that the carbon, nickel, and selenium can be a cost-effective alternative to gold for the rear contact. This study showcases how KSnI3 with inorganic charge transport layers stands as a prospective stable PSC with the potential to deliver clean, and green renewable energy solutions.

The development of a bilayer absorption scenario of CsPbI3/Cs2SnI6 PSCs for enhanced efficiency and stability

The introduction of heterojunction structures in perovskite solar cells (PSCs) can lead to substantial enhancements in power conversion efficiency (PCE) and stability. Using the SCAPS-1D software, we have theoretically investigated the performance potential of CsPbI3/Cs2SnI6 heterojunction PSCs. The purpose of incorporating a thin layer of Cs2SnI6 perovskite onto the CsPbI3 layer is to enhance the stability of the device through the formation of a protective barrier that prevents the continuous degradation of CsPbI3. The device's overall efficiency was found to be greatly enhanced by meticulously optimizing the acceptor concentration (NA), defect density (Nt), and absorber thickness of CsPbI3. In addition, the influence of various physical parameters such as the operating temperature, the work function of the metal rear contact, and series and shunt resistance on the photovoltaic performance of the device is comprehensively examined. With the systematic optimization of these parameters, the device exhibited improved performance and attained an outstanding PCE of 20.86 %, an open circuit voltage (VOC) of 1.19 V, a fill factor (FF) of 81.77%, and a current density voltage (JSC) of 21.32 mA/cm2. We think that our work will provide theoretical guidance in the advancement of heterojunction devices with much improved efficiency and stability.

Perspectives on life cycle analysis of solar technologies with emphasis on production in India

The COVID-19 pandemic impacted the solar power industry, business, and supply chain for 2019–2021, and installations are falling behind the mission plan. However, Indian PV manufacturers see it as a chance to engage in solar manufacturing to establish a competitive, sustainable, and robust domestic solar industry instead of import-based installations. Given the country's current environmental concerns, green and sustainable local manufacturing is the only viable alternative. By conducting a life cycle assessment (LCA), this study compared the environmental impacts generated by the five most promising photovoltaic technologies-mono-silicon, polysilicon, copper indium gallium selenide (CIGS), cadmium telluride (CdTe), and passivated emitter and rear contact (PERC) solar modules considering manufacturing in India. The study utilizes the ReCiPe method supported by Ecoinvent 3 databases and Simapro V9.0 software, and the functional unit for the data collection is in ‘per square meter’, which is later converted to ‘per kWh’ standard for comparison with the existing studies. The system boundary selected is from cradle to gate. The results demonstrate that cadmium telluride (CdTe) is the best technology for Indian climatic conditions in terms of environmental impact, with a global warming potential of 0.015 kg CO2 eq/kWh, stratospheric ozone depletion of 5.41E-09 kg CFC11 eq/kWh, human carcinogenic and non-carcinogenic toxicity of 6.67E-04 kg 1,4-DCB/kWh and 1.48E-02 kg 1,4-DCB/kWh, respectively and fine particulate matter formation of 3.96E-05 kg PM 2.5 eq/kWh assuming a lifetime of 25 years for these modules. CIGS follows CdTe in almost every environmental impact category.

High‐Performance Transparent Electron‐Selective Contact for Crystalline Silicon Solar Cells

AbstractHigh‐efficiency silicon solar cells featuring doped silicon layer‐based carrier‐selective contacts suffer from optical losses due to parasitic absorption. In this work, a high‐performance electron‐selective contact with high transparency is presented, consisting of intrinsic hydrogenated amorphous silicon (a‐Si:H) passivation layer, atomic‐layer‐deposited conductive magnesium oxide (MgOx) and low‐work‐function aluminium doped zinc oxide (AZO). The a‐Si:H/MgOx/AZO stack is demonstrated to be an excellent and transparent electron‐selective contact on c‐Si, featuring a small contact resistivity (ρc) of 56.0 mΩ cm2 and a low saturation current density (J0) of 2.9 fA cm−2 simultaneously. By the implementation of the a‐Si:H/MgOx/AZO front contact, a high power conversion efficiency (PCE) of 23.3% is achieved on silicon heterojunction (SHJ) solar cells, featuring an absolute short‐circuit current density (Jsc) and PCE gain of 1.3 mA cm−2 and 1.2%, respectively, compared to the conventional phosphorus‐doped silicon layer‐based electron‐selective contact. Moreover, a state‐of‐the‐art PCE of 22.8% is obtained on c‐Si solar cells with dopant‐free asymmetric heterocontacts on both sides, featuring an a‐Si:H/MgOx/AZO front contact and an a‐Si:H/vanadium oxide (VOx) rear contact.

Development of Low-Cost c-Si-Based CPV Cells for a Solar Co-Generation Absorber in a Parabolic Trough Collector

Concentrator photovoltaics (CPVs) have demonstrated high electrical efficiencies and technological potential, especially when deployed in CPV–thermal (CPV-T) hybrid absorbers, in which the cells’ waste heat can be used to power industrial processes. However, the high cost of tracking systems and the predominant use of expensive multi-junction PV cells have caused the market of solar co-generation technologies to stall. This paper describes the development and testing of a low-cost alternative CPV cell based on crystalline silicone (c-Si) for use in a novel injection-molded parabolic hybrid solar collector, generating both, photovoltaic electricity and thermal power. The study covers two different c-Si cell technologies, namely, passive emitter rear contact (PERC) and aluminum back surface field (Al-BSF). Simulation design and manufacturing are described with special attention to fingerprinting in order to achieve high current carrying capacities for concentrated sunlight. It was determined that Al-BSF cells offer higher efficiencies than PERC for the considered use case. Solar simulator tests showed that the highly doped 4 cm2 cells (50 ohm/sq) reach efficiencies of 16.9% under 1 sun and 13.1% under 60 suns at 25 °C with a temperature coefficient of −0.069%(Abs)/K. Finally, options to further improve the cells are discussed and an outlook is given for deployment in a field-testing prototype.