TriLumina develops and manufactures flip-chip VCSEL technology used in 3D sensing applications that must meet automotive grade 1 temperature range (-40 degrees C to 125 degrees C) performance and be tested to high reliability standards and criteria (AEC-Q102). Advances in VCSEL efficiency, performance and automotive qualification of TriLumina's self-hermetic flip-chip VCSEL are discussed. TriLumina's VCSEL-on-board (VoB), surface-mount technology VCSEL is introduced.

The design and optimization of two-dimensional VCSEL arrays operating with duty-cycles from 2 to 5% (quasi-continuous-wave or QCW) operating at 940 nm are presented. Designs for nominal 8 W and 100 W peak power using TriLumina's flip-chip-bondable, back-side-emitting VCSELs are reviewed. Performance as a function of duty cycle, including peak power output, spectral width and beam divergence are presented. Performance from -40 degrees C to 125 degrees C, corresponding to automotive grade 1 requirements, is reviewed. Optimization of the VCSEL arrays as a function of the number of emitters per chip is analyzed for trends in wall-plug efficiency, slope efficiency and operating conditions.

Comparison of performance prediction, expected energy production and actual energy production for Suncore's 50 MW and 60 MW Concentrator Photovoltaic (CPV) power plants in Golmud, China are reviewed. The efficiency of the power plants is accurately predicted through the use of an individual module performance model with field derived derating factors. Both of the plants are operating at the predicted average AC efficiency of 19.5% with fluctuations based on the quality of the solar resource at the sites.

Performance metrics for Suncore’s utility-scale CPV deployments in China are reviewed. Predictions of energy production based on individual module performance and solar resource data will compared to measured energy production from the power plants.

In October of 2013, Suncore's 50MW solar power plant in Golmud, Anhui, China became fully operational. Performance parameter extraction for Suncore's 1090X DDM module, based on the Photovoltaic Array Performance Model developed at Sandia National Labs, will be presented. These extracted parameters, along with solar resource and environmental data from the site, were used to predict the energy production of the plant prior to installation. The measured solar resource and environmental conditions at the site will be compared to the typical data used for the energy production estimates. In addition, the predicted energy production will be compared to actual production of the field. The achieved derates will be compared to the upfront prediction of these losses.

Establishing the performance and reliability of silicone polymers in 1000X CPV applications is critical to producing a reliable product, as well as assuring customer confidence. Silicones are robust materials, but the CPV application environment is especially severe and silicone performance under such conditions has not been well documented. Targeted testing of silicone polymers is one technique to rapidly establish and compare the performance of these materials under highly stressed conditions. The targeted testing described in this work consisted of single variable stress tests in which one relevant stress was maximized and combined effects stress tests where the samples experienced stress more representative of field conditions. Optical transmission of the bulk silicone polymer decreased significantly within 50 hours at 175 degrees C with the UV and visible portions of the spectrum experiencing the largest changes. Optical transmission of the bulk silicone polymer did not change upon exposure to 350nm UV light at room temperature. Combined effects tests of several silicone polymers on-sun have shown that elimination of the UV portion of the solar spectrum greatly enhances silicone lifetime.

Ensuring 25-year reliability of a CPV system requires knowledge of potential failure modes and material deficiencies. While Emcore’s CPV system conforms to all IEC 62108 tests, additional tests to eliminate potential long term reliability concerns have been performed. Performance is evaluated through all levels of integration, from cell to module. Tests at the cell level include IEC 62108 tests where feasible, as well as several other tests to establish the ability of the cell to survive additional integration and perform well throughout the lifetime of the CPV module. At a receiver assembly and module level, potential reliability concerns are addressed through targeted testing, which consists of accelerated stress tests which are used to quickly evaluate material performance and designed stress tests which allow the determination of activation energies. With this information, expected lifetime can be assessed and reliability concerns mitigated. Test methodologies and results from cell, receiver assembly and full module are presented demonstrating that targeted stress testing at each level of integration is a viable approach to assessing potential CPV failure modes.

EMCORE's Concentrator Photovoltaic (CPV) systems use large-format Fresnel lenses to achieve 1090X concentration onto high-efficiency multi-junction solar cells. The use of Fresnel lenses is common in CPV systems due to their thin profile and light weight. EMCORE uses silicone-on-glass (SOG) lens technology, which provides a high-reliability, high-durability alternative to acrylic lenses. This paper describes performance variations of these lenses based on the Fresnel groove depth. Both the optical efficiency and temperature dependence of the optical system are evaluated as a function of groove depth.

The CPV application places severe demands on the mechanical and electrical performance characteristics of the materials employed in the solar cell structure. This is especially true for the interfaces between the active semiconductor and the metal layers that are needed for electrical connection to the external circuits. At these interfaces TCE mismatch can result in high levels of stress during temperature cycling that is a natural component of the CPV operating environment. As the industry moves from R&D into production, methods are needed for quickly assessing the mechanical and electrical integrity of the metal/semiconductor interface during CPV solar cell fabrication. To provide a level playing field for cell suppliers and CPV module manufactures, such a technique should be established as part of an industry accepted cell qualification or specification standard.In this paper we review a variety of metal adhesion test methods and then propose a novel application of the die shear technique for interrogating small metal features on CPV solar cells. We report experimental results from this method and correlate them with bulk material properties.

Four approaches to modeling multi‐junction concentrating photovoltaic system performance are assessed by comparing modeled performance to measured performance. Measured weather, irradiance, and system performance data were collected on two systems over a one month period. Residual analysis is used to assess the models and to identify opportunities for model improvement.

High-efficiency solar cells used in Concentrator Photovoltaic (CPV) Systems require reliable, high-performance electrical, thermal and optical interfaces. EMCORE has developed standard CPV receivers that provide these interfaces. These standard designs provide a tool for CPV system developers to validate their novel system designs without the cost and schedule impact associated with custom receiver design. Standard receivers based on EMCORE's 1cm × 1cm and 0.5cm × 0.5cm triple junction solar cells will be reviewed. The standard receivers incorporate design rules developed by EMCORE's CPV system development team and are implemented using Curamik's aluminum oxide direct-bond-copper (dbc) substrates. The designs include Curamik's dimple technology for stress relief. The dbc substrates provide the high electrical stand-off and low resistance required for CPV applications. EMCORE's designs incorporate box connectors for wire interconnection to the receivers and a bypass diode that allows for string operation during partial shadow conditions. All components are attached using a solder reflow process that provides low void content bonding and excellent thermal conductivity between the solar cell and its substrate. Data gathered during receiver assembly, including x-ray data showing void content, will be reviewed. Methods and results for thermal resistance measurements will be presented. In addition we will review features included in the dbc that allow for component placement control. Receiver performance data as measured by HIPSS (High-Intensity Pulsed Solar Simulator) at 1000X concentration will also be reviewed. EMCORE is currently providing pre-qualification samples of these receivers to CPV system developers while qualification of the receivers is completed. The qualification test plan for the receivers will be reviewed and preliminary data from the qualification tests will be presented.

Demonstrated or predicted system reliability has become one of the most important requirements for the financing of CPV deployments. In this paper national and international CPV systems and other optoelectronic product qualification standards and guidelines are reviewed for applicability to solar cells and receivers. Comparisons are made to the operating conditions, reliability and lifetime expectations for other optoelectronics devices and applications. From these test plans are established for the CPV solar cell and receiver package reliability studies carried out at Emcore. Test protocols along with observed results for CPV cells and receivers are summarized.