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We demonstrate high efficiency triple junction solar cells with submillimeter dimensions in an all-back-contact architecture. 550 × 550 μm2 cells flash at 41.3% efficiency under the air mass 1.5 direct normal spectrum at 50 W/cm2 at 25 °C. Compared to standard size production cells, the micro cells have reduced performance at 1-sun due to perimeter recombination, but the performance gap closes at higher concentrations. Micro cells integrated with lens arrays were tested on-sun with an efficiency of 34.7%. All-back-contact architecture and submillimeter dimensions are advantageous for module integration and heat dissipation, allowing for high-performance, compact, lightweight, and cost-effective concentrated photovoltaic modules.

We propose a novel concept of thin and compact CPV modules in which submillimeter solar cells are directly attached to lens arrays without secondary optics or an extra heat sink. With this small cell size, the optical path length of the module can be brought down to one-twentieth that of conventional CPV modules. To achieve precise alignment of the microsolar cells at the lens focal points, we have developed a fluidic self-assembly technique that utilizes surface tension. This novel CPV module with triple junction microsolar cells demonstrated an efficiency of 34.7% under sunlight in the particular measured condition.

We present a fully monolithically integrated long vertical cavity surface emitting laser using an InGaAs/GaAs/AlGaAs gain medium directly bonded to a glass substrate with a concave micromirror. The lasing wavelength is 980nm with a threshold of 20mA for a 52microm mesa, differential quantum efficiency of 58%, and maximum output power of 39mW.

We have developed a compact concentrator photovoltaic (CPV) module that comprises micro-solar cells with an area of ≈0.6 × 0.6 mm2 sandwiched between a 20-mm-thick lens array and a 1-mm-thick circuit board with no air gap. To establish electrical connections between the circuit board and the micro-solar cells, we developed a micro-solar cell with positive and negative electrodes on the lower face of the cell. In this study, we demonstrated the photovoltaic performance of the micro-solar cell closely approaches that of the standard solar cell measuring ≈5 × 5 mm2 commonly used in conventional CPVs under concentrated illumination. Our study showed that the negative effect on PV performance of perimeter carrier recombination in the micro-solar cell was insignificant under concentrated illumination. Finally, we assembled our micro-solar cells into a CPV module and achieved the module energy conversion efficiency of 34.7% under outdoor solar illumination.

We propose a thin and compact concentrator photovoltaic (CPV) module, about 20mm in thickness, one tenth thinner than those of conventional CPVs, to enlarge CPV application scenarios, and achieved an energy conversion efficiency of 34.7%.

No abstract

We have developed a compact concentrator photovoltaic (CPV) module that comprises micro-solar cells with a cell size of ~ 0.6 mm × 0.6 mm, sandwiched between a 20 mm-thick lens array and a 1 mm-thick circuit board, with no air gap in the structure. To establish electrical connection between the circuit board and the micro-solar cells, we developed a micro-solar cell structure with via-holes through which the cathode and the anode on the upper face of the cell are electrically connected to electrodes patterned on the lower face of the cell. In this study, we demonstrated that the energy conversion efficiency of the micro-solar cell was close to that of a standard solar cell with dimensions ~ 5 mm × 5 mm, which is commonly used in conventional CPV systems. Our study shows that perimeter carrier recombination effects in micro-solar cells do not impact the performance significantly under concentrated illumination. We assembled our micro-solar cells into a CPV module and demonstrated the module energy conversion efficiency of 33.3% under solar illumination.