A new thermodynamic limit for the open circuit voltage of solar cells that includes thermalization is obtained in terms of photon entropy. A simple graphical construction makes it possible to link this limit to the existing limits for single junction cells due to Trivich and Flinn, Shockley and Queisser, Würfel, and the thermodynamic Carnot-type limit for hot-carrier solar cell. At the fundamental level, this limit points to similarity between photovoltaic and thermoelectric energy conversion.
In this work, we demonstrate the formation of local boron-doped, SiOₓ/p + poly-Si structures using wet chemical etching by direct printing of boron-ink. FlexTrail printing uses a very hollow (orders of μm for diameter) glass capillary tube filled with boron ink for printing onto silicon substrate. This process represents a mask-free approach for the formation of local TOPCon structures, enabling high-efficiency tunnel oxide passivating contact (TOPCon) solar cells. The factors influencing etch-back selectivity between intrinsic and boron-doped poly-Si were thoroughly investigated. It was determined that pre-treatment with diluted HF (1 wt%) prior to poly-Si removal in a KOH solution is the most critical step to achieve optimal etch selectivity. This treatment effectively removes the native oxide on intrinsic poly-Si while preserving the boron silicate glass (BSG) layer on p + poly-Si, facilitating the selective removal of intrinsic poly-Si and the formation of p + TOPCon structures. Line widths ranging from 24.0 to 100.5 μm on planar surfaces and 40.0–86.0 μm on textured surfaces were achieved. FlexTrail printing allows for significantly lower (and higher) feature sizes, but its fine-line potential was not fully exploited here due to alignment challenges during post-processing. Test structures with a line grid of local TOPCon structures exhibited a maximum open-circuit voltage (𝑖VOC of 720 mV and a lowest saturation current density (𝐽0𝑆𝐸) of ~90–120 fA/cm2. The developed local p + poly-Si will be integrated into high-efficiency TOPCon solar cells, where p + poly-Si will be strategically placed under the metal contact, in the near future.
Wang, Q, Guo, K, Gu, S, Huang, W, Wu, W, and Ding, J. Investigation on Effects of the Laser-Enhanced Contact Optimization Process With Ag Paste in a Boron Emitter for n-TOPCon Solar Cell. Progress in Photovoltaics. 2025; 33: 294–308.
In Section 3.3 “I–V Parameters,” the text “a 0.28 mA/cm2 increase in Jsc” was incorrect. This should have read: “a 0.08 mA/cm2 increase in Jsc.”
In Paragraph 2 of the “Conclusion” section, the text “a 0.28 mA/cm2 increase in Jsc” was incorrect. This should have read: “a 0.08 mA/cm2 increase in Jsc”.
We found that the data of the article are inconsistent with Table 2; the data in the table are correct; an error occurred while writing.
We apologize for this error.
This study evaluates the performance of three photovoltaic (PV) module operating temperature models—Ross, Faiman, and PVsyst®—using various measurement time resolutions for bifacial PV systems under various albedo conditions. This work also includes the application of these models using effective irradiance – incorporating both front and rear-side plane of array irradiance – for the estimation of bifacial PV module temperature. The calculated heat transfer coefficients for each evaluated scenario are presented and discussed in detail. A comprehensive comparison of all simulated scenarios was carried out to recommend the most suitable model for each condition. Additionally, the use of estimated cell operating temperature from back-of-module temperature was evaluated across all scenarios. As expected, hourly resolutions provided better results for all scenarios, having the lowest error for temperature estimations across different models and ground (albedo) types. Accounting for rear-side irradiance and using calculated coefficients led to more accurate temperature predictions, emphasizing the importance of model adaptations and precise parameterization. The results for different heat transfer coefficients varied significantly among the models. Ross's model, when applied with standard values (k between 0.02 and 0.04) showed close alignment with measured data. In contrast, Faiman's model with standard coefficients ( between 24 and 27 W/m2·°C, between 6 and 8 W/m2·°C/m/s) and PVsyst's standard coefficients ( = 29 W/m2·°C, = 0 W/m2·°C/m/s) exhibited significant deviations. Adjusted coefficients for PVsyst® ( = 40 W/m2·°C, = 0 W/m2·°C/m/s) provided better accuracy. The standard PVsyst® coefficients presented better results when compared against cell-adjusted temperature estimates, rather than back-of-module measured values. This discrepancy can lead to significant estimation errors in both temperature output performance and for bifacial modules.
Silicon heterojunction technology (HJT) and tunnel oxide passivated contact (TOPCon) solar cell technologies are expected to dominate the photovoltaic market in the coming years. However, there are still some concerns about the long-term stability of these technologies. This work examines the effects of two widely used commercial soldering fluxes (Flux A and Flux B) on the stability of commercial silicon HJT and TOPCon solar cells. The soldering flux was applied to the solar cells, and the solar cells were annealed at 85°C under a relative humidity (RH) of 0%. The investigated TOPCon solar cells were found to be stable; however, significant degradation was observed in the HJT solar cells after only 50 h. The efficiency of the HJT cells decreased by ~61%rel with Flux A and ~55%rel with Flux B, respectively. We attribute part of the observed degradation to pores present in the HJT cell metallisation after printing, which allow the soldering flux to easily penetrate the contact and subsequently react with the paste constituents. In addition, we find that the indium tin oxide (ITO) layer is very sensitive to soldering flux, showing major cracks and significant peeling after 50 h of annealing. Consequently, this work shows that some soldering flux can react with the ITO layer, without requiring the presence of water. This suggests that certain types of soldering flux can harm HJT solar cells even after encapsulation without the need for moisture ingress. Therefore, paying more attention to the choice of soldering flux is essential, especially when working with HJT cells. It is strongly recommended that users perform comprehensive component analysis testing on soldering fluxes before their official use rather than solely relying on datasheets provided by suppliers.
We investigate rapid thermal processing (RTP) as alternative to the prolonged thermal annealing process used to form tunnel-oxide passivating contacts for silicon solar cells. The thermal treatment is generally followed by hydrogenation to passivate defects at the Si/SiOx interface. Whereas industrial manufacturing generally uses Cz wafers, research is often carried out with FZ wafers. Both types of wafers are prone to the formation of thermal defects in the bulk. To disentangle effects of the interface and the bulk, we assess the lifetime at different steps of the process sequence for both wafer types. We find that the initial bulk lifetime of our p-type FZ material is maintained for RTP up to temperatures of about 450°C, followed by a severe decay and eventually a moderate extent of recovery at temperatures above 800°C. Compared to FZ material, the initial bulk lifetimes in our p-type Cz material are slightly lower, but they are maintained on that level up to about 600°C. Beyond that temperature, the lifetimes also decay, but to a lesser extent than in the FZ material, and there is no curing at higher temperatures. Hydrogenation can partially passivate the bulk defects in FZ material, but the initial state is not recovered. In Cz material, it appears that RTP creates two different types of defects; for those created up to 800°C, the initial state can be recovered by hydrogenation whereas those created at higher temperature cannot be passivated by hydrogenation. We also investigate the formation of n-type passivating contacts by RTP, and we fabricate solar cell precursors with a single RTP step and the same hydrogenation for both contact polarities. After sputtering a transparent conducting ITO layer on the full area and an Ag metallization, we achieve solar cells efficiencies up to 20.5%.
The application of (Zn, Mg)O buffer layers significantly improves the energy band alignment and the interface quality of the heterojunction of CZTSSe solar cells, leading to a breakthrough in power conversion efficiency (PCE). However, (Zn, Mg)O thin films prepared by sputtering typically exhibit poor crystallinity, limiting their application. Rapid thermal processing (RTP) and substrate heating during the sputtering are investigated to address this issue. Our study demonstrates the effectiveness of RTP in reducing oxygen vacancies (VO) and adsorbed oxygen (Oad). Furthermore, it is identified that both thermal treatments increase the MgZn/(MgZn + Zn) ratio of (Zn, Mg)O thin films, thereby increasing their band gap. A notable improvement in the device performance of CZTSSe solar cells, particularly in fill factor (FF) and open-circuit voltage (VOC), is achieved by adopting optimal thermal treatment processes. Power conversion efficiencies (PCEs) of 12.4% and 12.3% are obtained through RTP and substrate heating, which are remarkably improved compared with the untreated CZTSSe solar cells with the maximum PCE of 9.5%. Notably, 12.4% is the highest PCE for CZTSSe solar cells with (Zn, Mg)O buffers to date.
We present an analysis of the performance data of a monitored PV system onboard a light commercial electric vehicle during parking and driving conditions in the Hannover region of Germany. The PV system's nominal power is 2180 WP with flat silicon modules on the vehicle's roof, rear, left, and right sides and other electronic components needed to charge the vehicle's high-voltage (HV) battery. The analysis indicated that after 488.92 h of operation, the modules mounted on the vehicle roof produced 133.32 kWh of electricity during parking at the best possible orientation compared to 15.4, 30.67, and 22.99 kWh for the modules mounted on the rear, left, and right sides, respectively. During the trips, after 31.99 h of operation, 6.12, 0.68, 1.08, and 1.86 kWh of electricity were produced by the modules on the roof, rear, left, and right sides, respectively. The overall system efficiency was in the 60%–65% range. The aggregated usable electricity reaching the HV battery after multiple conversion stages generated by the system at the two parking locations was 129.39 kWh. PV electricity generated at the two parking locations enabled a range extension of approximately 530 km, which is 30% of the total distance driven during the measurement period between April and July 2021.
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