Planar micro-tracking concentrator photovoltaic modules hold great promises, as they enable the combination of efficiencies greater than 30% with the form factor of conventional rooftop panels operating at fixed tilt. Over the past three years, Insolight has been developing a fixed-tilt system, combining a biconvex silicone lens array, high efficiency multi-junction cells and integrated micro-tracking. A first prototype built in 2016 was validated with a peak conversion efficiency of 36.4 %. On the path towards industrialization of the systems, we present the evolution from the first lab prototype to fully automated panels featuring several thousands cells, installed on a rooftop pilot site. Continuous operation and data logging of the outdoor installation over a year enable us to validate a simple and robust integrated micro-tracking scheme. Recent measurements showed a module efficiency of 29% at concentrated standard test conditions. Different hybrid PV-CPV architectures are under evaluation for the capture of global irradiance.

Soiling is the major cause of power loss of photovoltaics (PV) and concentrated solar power (CSP) in desert areas. Electrodynamic cleaning system (EDS) is an automatic and water‐free integrated cleaning system for mirrors or solar panels, which uses pulsed electric fields to remove dust off their surface. The first EDS field test over a long period on PV modules is reported here and shows a clear effect on soiling reduction in real conditions in Saudi Arabia. A total of 458 days of measurements is analyzed, and depending on the considered periods, performance losses due to soiling (soiling rate) can vary from −0.06%/day to −0.41%/day for a reference module, while the relative soiling rate reduction using an EDS can be up to 95.7% with an average of 32.1%. Cost calculations demonstrate an added value of the modules equipped with the EDS between 2.6 and 5.2 ¢/Wp compared with usual cleaning system, which is nearly between 10% and 20% of the module price.

The power produced by a photovoltaic module is not simply the sum of the powers of its constituents cells. The difference stems from a number of so-called "cell-to-module" (CTM) gain or loss mechanisms. These are getting more and more attention as improvements in cell efficiency are becoming harder to achieve. This work focuses on two CTM mechanisms: the gain due to the recapture of light hitting the apparent backsheet in the "empty" spaces around the cells and the loss from the serial connection of "mismatched" cells i.e. with different maximum power points. In general, for insulation purposes, the spaces on the edges of modules are larger than the spacing between cells. This study reveals that, when reflective backsheets are used, these "edge spaces" provide an additional current boost to the cells placed at the edges that can lead to a 0.5% gain in the output power of modules (with 60 or 72 cells). This location-dependent current boost adds to the usual variations in cell characteristics dictated by the binning size and results in larger "cell-to-cell mismatch losses". However, the simulations reveal that for short-circuit current bin size smaller than 5%, this additional mismatch loss is lower than 0.05%. All considered, this study demonstrates that the spaces at the edges of PV modules have a significant impact on the cell to module ratios (approximate to+ 0.5% abs or approximate to 16% of the CTM gains) when reflective backsheets are used.

Thin-film silicon layers deposited in parallel-plate PECVD reactors can be produced with varying microstructure, composition and properties, depending on deposition process conditions and on the underlying substrate properties. This allows for designing selective contacts well suited to limit recombination losses in wafer-based crystalline silicon solar cells. For such heterojunction selective contacts, we demonstrate that an hydrogenated amorphous silicon passivation layer with a high microstructure factor yields enhanced passivation, demonstrating > 30 ms carrier lifetime on 270 μm Fz wafer. Combining the developed intrinsic material together with doped layers with appropriate activation energy and defect density, we show silicon heterojunction solar cells with fill factor > 82 % and with certified efficiency up to 23.88 %. In addition, we report on PECVD process conditions impact on the functionality of back-contacted silicon heterojunction solar cells based on the innovative “tunnel-IBC” approach, which uses an advanced control and utilization of thin film silicon specific properties. A certified 24.42 % tunnel-IBC solar cell is reported, demonstrating the potential of this simple manufacturing approach for back-contacted devices. Advanced processing of thin film silicon layers is therefore demonstrated to enable for achieving high efficiency crystalline silicon devices.

Silicon heterojunction solar cells without metallization can be interconnected using SmartWire Connection Technology (SWCT). The module performances can be comparable to standard SWCT module and the electrical contact of wire to transparent conductive oxide (TCO) is stable during more than 200 thermo-cycles between -40°C to +85°C. Costs comparison shows that direct contact to TCO is still more expensive than standard SWCT using indium-tin coating. By switching to indium-free wire, the cost parity can be reached.

Extensive knowledge of the dependence of solar cell and module performance on temperature and irradiance is essential for their optimal application in the field. Here we study such dependencies in the most common high-efficiency silicon solar cell architectures, including so-called Aluminum back-surface-field (BSF), passivated emitter and rear cell (PERC), passivated emitter rear totally diffused (PERT), and silicon heterojunction (SHJ) solar cells. We compare measured temperature coefficients (TC) of the different electrical parameters with values collected from commercial module data sheets. While similar TC values of the open-circuit voltage and the short circuit current density are obtained for cells and modules of a given technology, we systematically find that the TC under maximum power-point (MPP) conditions is lower in the modules. We attribute this discrepancy to additional series resistance in the modules from solar cell interconnections. This detrimental effect can be reduced by using a cell design that exhibits a high characteristic load resistance (defined by its voltage-over-current ratio at MPP), such as the SHJ architecture. We calculate the energy yield for moderate and hot climate conditions for each cell architecture, taking into account ohmic cell-to-module losses caused by cell interconnections. Our calculations allow us to conclude that maximizing energy production in hot and sunny environments requires not only a high open-circuit voltage, but also a minimal series-to-load-resistance ratio.

In this work, we investigate the temperature and irradiance dependencies of the power output of silicon solar cell architectures (BSF, PERC, PERT, SHJ). When we compare our data with commercial module datasheets, we find that the temperature coefficient under maximum power point conditions is systematically worse in the modules. Following our analysis we attribute this to ohmic losses (RCTM) due to cell interconnection. Using energy yield calculations we show the impact of RCTM on the energy production in moderate and hot and sunny climates for all investigated architectures. We conclude that maximizing energy production in hot and sunny environments requires not only a high open-circuit voltage, but also a minimal series-to-load-resistance ratio.

The silicon heterojunction (SHJ) technology has already proven its ability to produce high-efficiency devices, and very competitive production costsat the mass production level can be potentially reached by integrating latest developments. In this work, several of such technology developments are presented related to the PECVD and metallization steps. PECVD processes were developed in a large-area reactor, showing excellent thickness uniformity over the full reactor area (< 4%) and state-of-the-art passivation level (> 16ms). Improvements in screen-printing permitted to reduce the finger width down to 40μm. A 21.9% 6-inch busbar-less cell with only 25mg of Ag was produced, resulting in Ag cost of only 0.22 €cts/Wp. A complete SHJ process for full-area 6-inch cells has been established using industry-compatible processes, with a record efficiency of 22.8% and Vocs above 740mV (CZ n-type). The use of 4 cm2 SHJ cells for low-concentration applications was investigated at different illumination levels and temperatures. With optimized front grid designs (Cu electro-plated fingers), efficiencies can be maintained around 20% at 10 suns. Thanks to a temperature-assisted improvement in carrier transport, the cell temperature coefficient improves with illumination, showing even positive values above 35 suns. This suggests a strong potential of SHJ cells for low-concentration PV.