A high concentration photovoltaic module utilizing micro-transfer printing and surface mount technology

We describe a high concentration photovoltaic (CPV) module utilizing micro-transfer printed (μ-TP) dual-junction GalnP/GaAs solar cells and an ELO (Epitaxial Lift-Off) process used to fabricate very small cells (<;0.5 mm²) using 1^st use and reused GaAs substrates. The benefits of this technology include high efficiency, simple distributed heat transfer at high concentration ratios, and short optical paths. This approach enables the use of low cost, high reliability surface mount assembly of large backplanes for integration into CPV modules. To minimize compound semiconductor use and maximize cell efficiency, we combine plano-convex primary and spherical secondary optics to concentrate sunlight 1000X over a +/-0.8 degree angle of acceptance. Receiver efficiencies of ELO dual-junction GalnP/GaAs cells of >30% at 1,000 sun concentration are reported. Coupled with a >80% efficient optical train, module efficiencies greater than 24% have been achieved with dual-junction μ-TP solar cells.