Low Concentrator Photovoltaic Receiver for Wireless Laser Power Transmission

The development of wireless laser power transmission (WPLT) technology has the potential to revolutionize the way power is delivered to remote or hard-to-reach locations. However, its practical deployment is constrained by several factors, including optical alignment requirements, atmospheric losses, conversion efficiency, eye and fire safety considerations, and the effects of non-uniform or dynamic irradiance on photovoltaic receivers.

To address these challenges, researchers from Spain's University of Jaén have fabricated a low-concentrator photovoltaic (LCPV) receiver incorporating a crossed compound parabolic concentrator (CCPC) to improve optical coupling under static yet inherently non-uniform laser irradiance. The system is intended for applications in WPLT, which offers a promising approach for delivering power over distances without physical connections.

The researchers developed and experimentally demonstrated a 3 × 3 low-concentrator photovoltaic receiver that combines optimized cell interconnections with CCPC optics to improve power-conversion efficiency and angular tolerance under non-uniform laser illumination.

The system integrates a 3 × 3 array of 20 × 20 mm² monocrystalline silicon cells with interdigitated back-contact (IBC) architecture, with each cell being coupled to the CCPC redirecting incident radiation toward the cells while providing a wide acceptance angle under static illumination.

| **Component** | **Value** | | --- | --- | | Entrance aperture | 2.5 times the cell area | | Reduction in semiconductor material | 60% | | Frontal aperture | 104 × 104 mm² | | Measured mass | 123 g |

The CCPC geometry was optimized with an entrance aperture 2.5 times the cell area, enabling a 60% reduction in semiconductor material compared with an equivalent non-concentrated receiver. The concentrators were fabricated from polymethyl methacrylate (PMMA), selected for its high optical transmittance, favourable dielectric properties and ease of manufacturing.

The electrical response of each of the nine cells was measured at different incident powers and angles to evaluate optical-electrical coupling and the effects of non-uniform illumination. Mismatch losses were then calculated for different series and parallel interconnection schemes by comparing the measured module power with the ideal sum of the individual cell maximum-power outputs.

The electrical measurements confirmed that short-circuit current was the dominant source of cell-to-cell variation, ranging from below 0.1 A in peripheral cells to about 0.45 A in the central cell at 5 W. By contrast, open-circuit voltage and fill factor remained relatively stable, indicating that current mismatch is the principal limitation at the module level.

The researchers also found that grouping cells according to similar photocurrent significantly reduced these losses, with the ring interconnection architecture producing almost the same output as the ideal mismatch-free configuration. At 5 W, ring losses remained below 3%, compared with more than 58% for the series configuration and approximately 6% for the parallel configuration.

Moreover, the ring configuration achieved power conversion efficiency values close to 16.3% at 806 nm, compared with 6.9% for series and 15.2% for parallel interconnection, while the theoretical optimum at 955 nm reached 18.4%.

The team also explained that the receiver demonstrated relatively good angular tolerance, with maximum power generally remaining at 80-90% of its nominal value at 30° incidence. At 45°, however, photocurrent and maximum power decreased substantially as beam displacement exceeded the effective collection area.

Overall, the results demonstrate that effective current-balancing strategies and tailored interconnection schemes are essential for achieving high-efficiency laser-powered photovoltaic reception under realistic irradiation conditions.