Kevin Lynn

CuIn1−xGaxSe2 thin film solar cells by two-selenizations process using Se vapor

Abstract A novel process consisting of two-selenizations of magnetron sputtered metallic precursors using Se vapor and a method for Ga incorporation using a single Cu Ga(22 at.%) alloy target without deleterious indium-gallium interaction have been developed for preparation of well-adherent, large, compact, well-faceted-polyhedral-grain CuIn 1− x Ga x Se 2 thin films having optimum composition of Cu:In:Ga:Se in atomic percent of 24.25:22.21:4.40:49.14. Higher indium proportion in the first precursor resulted in elimination of pits in the CuIn 1− x Ga x Se 2 films, which made them more suitable for preparation of solar cells with thin US heterojunction partner layers. Optimized selenization parameters with the maximum temperature of 550–560°C and a Se vapor incidence rate of 50–75As −1 resulted in improved morphology and enhanced gallium content of completed CuIn 1− x Ga x Se 2 thin films. The best solar cell had an open-circuit voltage V oc of 451.8 mV, a short-circuit current density J sc of 34.5 mA, a fill factor of 57.87%, a total-area efficiency of 9.02%, and a fairly constant spectral response over the entire spectral range.

Updating technical screens for PV interconnection

Solar photovoltaics (PV) is the dominant type of distributed generation (DG) technology interconnected to electric distribution systems in the United States, and deployment of PV systems continues to increase rapidly. Considering the rapid growth and widespread deployment of PV systems in United States electric distribution grids, it is important that interconnection procedures be as streamlined as possible to avoid unnecessary interconnection studies, costs, and delays. Because many PV interconnection applications involve high penetration scenarios, the process needs to allow for a sufficiently rigorous technical evaluation to identify and address possible system impacts. Existing interconnection procedures are designed to balance the need for efficiency and technical rigor for all DG. However, there is an implicit expectation that those procedures will be updated over time in order to remain relevant with respect to evolving standards, technology, and practical experience. Modifications to interconnection screens and procedures must focus on maintaining or improving safety and reliability, as well as accurately allocating costs and improving expediency of the interconnection process. This paper evaluates the origins and usefulness of the capacity penetration screen, offers potential short-term solutions which could effectively allow fast-track interconnection to many PV system applications, and considers longer-term solutions for increasing PV deployment levels in a safe and reliable manner while reducing or eliminating the emphasis on the penetration screen.

Still Shining: Solar Energy Is Becoming Mainstream [Guest Editorial]

The articles in this special issue focus on solar power generation, including new technologies, services, and applications.

Current results of the US DOE high penetration solar deployment project

The SunShot Vision Study defines a scenario for solar energy technologies to significantly contribute to meeting U.S. electricity demand. To achieve this, work is in progress to identify, quantify, and address the impacts of high levels of distributed PV generation on electric distribution systems. The Department of Energy (DOE) Solar Energy Technologies Program (SETP) initiated a project to gain experience and to identify and quantify these potential impacts, develop and verify models of these systems, evaluate methods for mitigating any impacts, and develop potential solutions. This paper summarizes the current progress of the six competitively selected projects.

Photovoltaic systems interconnected onto secondary network distribution systems

While the number of PV systems interconnected to the electric grid has increased significantly over the last decade, only recently have PV systems been installed in major metropolitan areas and tied to electric distribution secondary network systems (networks). This paper examines six cases studies of photovoltaic (PV) systems integrated into secondary network systems. The six PV systems were chosen for evaluation because they are interconnected successfully to secondary network systems located in four major U.S. Cities.

Techniques for increasing Ga content in CuIn1−xGaxSe2 thin films prepared by two-stage selenization process

A Cu-Ga(66 at. %) alloy target was employed for enhancing the gallium content in CuIn1−xGaxSe2 films prepared by two Se-vapor selenizations of metallic precursors. Combination with a Cu-Ga(22 at. %) sputtering target allowed preparation of CuIn1−xGaxSe2 films with a graded profile. Gallium content Gax near the surface was raised to the range 0.28–0.32, while an even higher amount of gallium of up to 0.40 was obtained in the bulk of the films. Efficiency of solar cells prepared from CuIn1−xGaxSe2 films with moderately enhanced gallium content was 8.5%. Higher gallium proportions seem to be correlated with the formation of Cu-rich phases, surface inhomogeneities, and possibly a highly resistive phase. This combined with inferior crystallinity deteriorated solar cell efficiency.

Power to the People [Guest Editorial]

The last two years have seen a tremendous increase in the number of installed solar energy systems. In 2010, annual grid-connected photovoltaic (PV) installations in the United States and worldwide were expected to be about 0.8 GW and 16–18 GW, respectively. At the end of 2010, the cumulative installed base of grid-connected PVs in the United States and worldwide was about 2 GW and about 40 GW, respectively. One of the areas that has been receiving much attention recently is large utility-scale solar systems.

Polycrystalline CuIn/sub 1-x/Ga/sub x/Se/sub 2/ thin film PV solar cells prepared by two-stage selenization process using Se vapor

Novel two-stage Se vapor selenization of magnetron sputtered metallic precursors and Ga incorporation using single Cu-Ga(22 at.%) alloy target have been developed for preparation of well-adherent, large, compact, well-faceted polyhedral grain CuIn/sub 1-x/Ga/sub x/Se/sub 2/ thin films having optimum composition Cu:In:Ga:Se of 22.95:25.03:1.40:50.63. Cu-In-Ga precursor homogenization by in situ heat-treatment at /spl sim/90/spl deg/C for 10 minutes prior to first selenization, selenization temperature of 550-560/spl deg/C, and Se vapor incidence rate of 50 /spl Aring/ sec/sup -1/ resulted in improved morphology of completed CuIn/sub 1-x/Ga/sub 2/Se/sub 2/ thin films, and solar cells with open circuit voltage V/sub oc/ 377 mV, short circuit current density J/sub sc/ of 34.8 mA, fill factor (FF) of 62.5%, active area efficiency of 8.2% (total area efficiency 5.8% limited by FF 49.1%) and fairly constant spectral response over the spectral range.

Special Section Guest Editorial: Guest Editorial: Special Section on Reliability of Photovoltaic Cells, Modules, Components, and Systems

The field of photovoltaics has undergone dramatic growth over the past few years. This growth has been accompanied by two significant changes in the commercial photovoltaic (PV) market. 1.The major PV market has shifted from the residential and commercial building markets to central station utility power markets. With this switch has come a new focus on the long-term reliability and durability of PV modules and systems. If you are installing tens or even hundreds of megawatts of PV modules, it is absolutely necessary to ensure that they will continue to perform adequately throughout their expected lifetime of at least 25 years. 2.Selling prices for PV modules have decreased from more than

Is the Distribution Grid Ready to Accept Large-Scale Photovoltaic Deployment? State of the Art, Progress, and Future Prospects

4 per watt to less than