• Energy Research

Ultraviolet (UV)‐induced degradation (UVID) poses a significant challenge for the prospective mass production of silicon heterojunction (SHJ) solar cells, known for their high efficiency. In this study, the magnified impact of UV radiation when employing a silicon carbide (SiC)‐based transparent passivating contact (TPC) on the front side of SHJ solar cells is reported. A reduction in open‐circuit voltage (VOC), short‐circuit current (JSC), and fill factor of 12%, 6%, and 11%, respectively, is observed after UV exposure. Conventional UVID mitigation measures, UV‐blocking encapsulation, are assessed through single‐cell TPC laminates, revealing an unavoidable tradeoff between current loss and UVID. Alternatively, the utilization of ultraviolet‐downshifting (UV‐DS) encapsulants is proposed to convert UV radiation into the visible light spectrum. An optical simulation method, conducted via OPAL2, is presented to evaluate UV‐DS encapsulants for diminishing UVID in SHJ solar cells with different front contacts. A simple methodology is proposed to mimic the optical property of UV‐DS encapsulants. In the simulation results, additional current gains of up to 0.33 mA cm−2 achievable with suitable UV‐DS encapsulants are highlighted. The factors related to the UV‐DS effects are evaluated and the optimization pathway for UV‐DS encapsulants is elucidated.

ABSTRACTWe 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.

I‑V measurements are sensitive to the number and positioning of current and voltage sensing contacts. For busbarless solar cells, measurement setups have been developed using current collection wires and separate voltage sense contacts. Placing the latter at a defined position enables a grid resistance neglecting measurement and thus I‑V characteristics independent from the contacting system. This technique has been developed for solar cells having a finger grid and good conductivity in the direction of the fingers. The optimal position of the sense contact in case of finger-free silicon heterojunction solar cells has not yet been studied. Here, the lateral charge carrier transport occurs in a transparent conductive oxide layer resulting in a higher lateral resistance. We perform finite difference method simulations of HJT solar cells without front metallization to investigate the impact of high lateral resistances on the I-V measurement of solar cells. We show the high sensitivity on the number of used wires for contacting as well as the position of the sense contact for the voltage measurement. Using the simulations, we are able to explain the high difference of up to 7.5% in fill factor measurements of metal free solar cells with varying TCO sheet resistances between two measurement systems using different contacting setups. We propose a method to compensate for the contacting system to achieve a grid-resistance neglecting measurement with both systems allowing a reduction of the FF difference to below 1.5%.

A unique life cycle assessment highlights the potential of photovoltaics to limit the global warming potential of hydrogen imports, using Germany's domestic supply as a reference.

AbstractWe investigate the scattering behavior of nano‐textured ZnO–Air and ZnO–Silicon interfaces for the application in thin film silicon solar cells. Contrary to the common approach, the numerical solution of the Maxwell's equations, we introduce a ray tracing approach based on geometric optics and the measured interface topography. The validity of this model is discussed by means of scanning near‐field optical microscopy (SNOM) measurements and numerical solutions of the Maxwell's equations. We show, that the ray tracing model can qualitatively describe the formation of micro lenses, which are the dominant feature of the local scattering properties of the investigated interfaces. A quantitative analysis for the ZnO–Silicon interface at λ = 488 and 780 nm shows that the ray tracing model corresponds well to the numerical solution of the Maxwell's equations, especially within the first 1.5 µm distance from the interface. Direct correlations between the locally scattered intensity and the interface topographies are found. Copyright © 2011 John Wiley & Sons, Ltd.

The color produced by visible light that reflects from the photovoltaic modules can influence visual aesthetics for colored photovoltaic applications, such as the building integrated photovoltaic and the vehicles integrated photovoltaic. How two colors lying close together can be perceived by the human eye is important for aesthetic design. In this article, we investigate the reflectance spectra variation caused by the variation of indium tin oxide thickness and incidence angle of sunlight based on the well-known silicon heterojunction solar cells and modules. By converting the reflectance spectra into the Delta E 2000 value, we quantify whether differences in color can be perceived. The colors are also predicted based on the standard red, green, and blue color space. The results show that the reflectance variation because of an ITO thickness deviation of 5 nm in SHJ solar cells leads to a perceptible color difference, which can be suppressed after encapsulation but is still perceptible on close observation. The ITO thickness deviation should be controlled within 3 nm to produce a nearly imperceptible visual appearance. The color difference of SHJ modules with an ITO thickness of 70 nm is nearly imperceptible if the incidence angle is below 70°. For comparison, the color differences of the passivated emitter and rear contact solar cells using SiNx as an antireflection layer is also investigated.

<p>Photovoltaics (PV) in onboard vehicle applications adds weight to an electric vehicle (EV), increasing the overall energy consumption. Although the added PV system weight (1.5– 40 kg) is small compared to the vehicle weight (1500–2200 kg), the power generated by PV (55–700 W) is also very small com- pared to the power needed (up to 80–285 kW) to propel an EV, making the effect of additional PV system weight on energy con- sumption a non-trivial topic to analyze. We present a method to study the impact of vehicle onboard PV weight on the energy balance of EVs for different Vehicle-added PV (VAPV) and vehi- cle-integrated PV (VIPV) configurations with eight different PV technologies, using data from vehicle onboard measurement campaigns and simulations. Simulations are carried out for the driving phase of two electric cars (medium and large passenger cars). Our method calculates the energy consumption attributa- ble to the added PV system weight (0.05–1.4 Wh/km) and PV energy yield (0.12–3.12 Wh/km) for a selection of trips. The re- sults of these simulations are expressed through a newly intro- duced parameter called “onboard PV yield factor”, where posi- tive values indicate a net energy gain and negative values indicate a net energy loss of the onboard PV system. Our results show that the onboard PV yield factor for a VAPV configuration can range between -69.1 and 86.9 %, and for a VIPV configuration, between 77.2 and 89.7 %.</p>