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Since January 1993, ‘Progress in Photovoltaics’ has published six monthly listings of the highest confirmed efficiencies for a range of photovoltaic cell and module technologies 1, 2, 3. By providing guidelines for the inclusion of results into these tables, this not only provides an authoritative summary of the current state of the art but also encourages researchers to seek independent confirmation of results and to report results on a standardized basis. In a recent version of these Tables (Version 33) 2, results were updated to the new internationally accepted reference spectrum (IEC 60904-3, Ed. 2, 2008), where this was possible.
The most important criterion for inclusion of results into the tables is that they must have been measured by a recognized test centre listed elsewhere 1. A distinction is made between three different eligible areas: total area; aperture area and designated illumination area 1. ‘Active area’ efficiencies are not included. There are also certain minimum values of the area sought for the different device types (above 0.05 cm2 for a concentrator cell, 1 cm2 for a one-sun cell and 800 cm2 for a module) 1.
Results are reported for cells and modules made from different semiconductors and for subcategories within each semiconductor grouping (e.g. crystalline, polycrystalline and thin film). From the present version onwards, spectral response information will be included in the form of a plot of the external quantum efficiency (EQE) versus wavelength, normalized to the peak measured value.
Highest confirmed cell and module results are reported in Tables I, II and IV. Any changes in the tables from those previously published 3 are set in bold type. In most of the cases, a literature reference is provided that describes either the result reported or a similar result. Table I summarizes the best measurements for cells and submodules, Table II shows the best results for modules and Table IV shows the best results for concentrator cells and concentrator modules. Table III contains what might be described as ‘notable exceptions’. While not conforming to the requirements to be recognized as a class record, the cells and modules in this table have notable characteristics that will be of interest to sections of the photovoltaic community with entries based on their significance and timeliness.
Table I. Confirmed terrestrial cell and submodule efficiencies measured under the global AM1.5 spectrum (1000 W/m2) at 25°C (IEC 60904-3: 2008, ASTM G-173-03 global).
To ensure discrimination, Table III is limited to nominally 10 entries with the present authors having voted for their preferences for inclusion. Readers who have suggestions of results for inclusion into this table are welcome to contact any of the authors with full details. Suggestions conforming to the guidelines will be included in the voting list for a future issue. (A smaller number of ‘notable exceptions’ for concentrator cells and modules is additionally included in Table IV.)
Table IV. Terrestrial concentrator cell and module efficiencies measured under the ASTM G-173-03 direct beam AM1.5 spectrum at a cell temperature of 25°C.
Ten new results are reported in the present version of these tables.
The first new result in Table I is a new record for a single-junction cell of any type under non-concentrated sunlight. An efficiency of 26.4% is reported for a 1 cm2 GaAs cell fabricated and measured by the Fraunhofer Institute for Solar Energy Systems (FhG-ISE).
Another significant new result in Table I is the first single-junction amorphous silicon cell with stabilized efficiency above 10%. An efficiency of 10.1% is reported for a 1 cm2 cell fabricated by the Oerliken Solar Laboratory, Neuchatel 4 measured by the National Renewable Energy Laboratory (NREL) after stabilization at Oerliken.
The final new result in Table I is another increase (third in a row) to 9.2% efficiency for a 17 cm2 dye-sensitized submodule fabricated by Sony 5 and measured by the Japanese National Institute of Advanced Industrial Science and Technology (AIST).
Following the burst of activity in the multicrystalline silicon module area reported in the last version of these tables, where three groups exceeded the previous record for module efficiency over the reporting period, a fourth group has done even better. In Table II, a new efficiency record of 17.3% is reported for a large (1.3 m2 aperture area) module fabricated by Kyocera and measured by AIST.
Also reported in Table II is a record result for a thin-film module, with 13.8% reported for a 1 m2 CIGS module fabricated by Miasole and measured by NREL 6.
The first new result in Table III also relates to improved multicrystalline silicon cells. An efficiency increase to 19.3% has been confirmed by AIST for a large 218 cm2 multicrystalline silicon cell fabricated by Mitsubishi Electric 7.
Another new result in Table III is the improvement of a small area (0.50 cm2) CIGS cell fabricated by Zentrum für Sonnenenergie-und Wasserstoff-Forschung (ZSW), Stuttgart to 20.1% efficiency as measured by FhG-ISE. This cell is slightly bigger with a slightly higher measured efficiency than for the previous 20.0% result, but the cell is still smaller than the 1 cm2 size required for classification as an outright record.
The EQE normalized to the peak EQE values for seven of the above devices are shown in Figures 1(a) and (b).
Concentrator cell and module results (Table IV) are now referenced against the direct normal spectrum tabulated in ASTM G173-03 (except where otherwise noted). Three new results are reported.
The first is an increase in the efficiency to 29.1% at 117 suns for a GaAs cell fabricated and measured by FhG-ISE under the new reference spectrum, paralleling the new 1-sun result reported in Table I.
The second new result is a notable exception. An efficiency of 41.3% under 343 suns concentration is reported for a relatively large 1 cm2 triple-junction cell fabricated by Spire Semiconductor 8 and measured by NREL. This result is only slightly lower than the 41.6% outright concentrator cell record. The interesting feature is that the cell was fabricated by a new technique for a device of this level of performance. The top two cells (InGaP and GaAs) were grown epitaxially on one side of a GaAs wafer. The wafer had been flipped with the third cell, a 0.95 eV bandgap InGaAs cell, previously grown epitaxially on the opposite side 8.
Finally, a small (0.01 cm2) GaInP/GaAs tandem solar cell fabricated by the Universitat Politecnica de Madrid 9 and measured by FhG-ISE has shown exceptional performance at high sunlight concentration levels with 32.6% efficiency demonstrated from 500–1000 suns concentration (0.5–1 kW/m2 irradiance). This eclipses several previous results for double junction devices.
Figure 1(b) shows the normalized EQE of first and third of these concentrator cells, with the response of the two cells of the tandem stack shown separately. Also shown is the EQE similarly plotted for the 41.6% efficient triple-junction device reported in the previous version of these tables 3. More information on the EQE of other entries will be published in future issues.
While the information provided in the tables is provided in good faith, the authors, editors and publishers cannot accept direct responsibility for any errors or omissions.