Microscale solar cells for high concentration on polycrystalline Cu(In,Ga)Se2 thin films

Abstract

International audienceWe report high concentration experiments on polycrystalline thin film solar cells. High level regime is reached, thanks to the micrometric scale of the Cu(In,Ga)Se 2 cells, which strongly decreases resistive losses. A 4% absolute efficiency increase is obtained at a concentration of x120, and current densities as high as 100 A/cm² can be measured. These results show that the use of polycrystalline thin films under high concentration is possible, with important technological consequences

Monolithically interconnected lamellar Cu(In,Ga)Se2 micro solar cells under full white light concentration

“…Reducing the radius of the active cell area together with fixed dimensions for the contact area led the averaged FF values and hence the conversion efficiency drop from 16.0 to 13.6% in case of 2150-μm and 750-μm ACW dot-cells, respectively. Similar results for CIGSe-microcells were published by M. Paire et al with initial efficiencies at 1 sun ranging between 12.8 and 14.5% [9,10,12].…”

“…It is further to consider, that the finally estimated R s and R p values reflect the sum of different particular single serial and parallel resistances that vary on the material, contacts and geometry used and that may change differently during concentration. M. Paire et al discuss in addition a reduction of R s related to a shift into the "high injection regime" [10]. Own tests in that field showed a change in specific resistivity by one order of magnitude from 2885 Ohm cm at 1 sun to 246 Ohm cm at 33 suns.…”

“…To optimize photovoltaic devices further new technological enhancements are necessary. One potential and promising way is the implementation of photon managing elements, like light guiding structures [5,6], spectral converter layers [7] or light concentrating lenses [8][9][10][11][12][13][14][15]. By combining light concentrating elements with solar cells, the cell area and hence the used absorber material can be reduced by 1 to 2 orders of magnitude without power loss.…”

Thin-film micro-concentrator solar cells

“…However, under concentration it performed worse, reaching its maximum efficiency of ∼21.3% at 30 suns, while the untreated sample continued to improve in efficiency to 22.7% at 100 suns, the highest concentration factor measured. The authors found the series resistance of the absorber itself to be important, similar to Paire et al [36].…”

“…In 2011, Paire et al [36] realized a circular micro solar cell, where the Mo back contact, CIGSe absorber layer, CdS buffer layer and the i-ZnO are continuous large-area layers, but the ZnO:Al window layer is restricted to a 15 μm diameter by means of a SiO 2 insulating dielectric layer (see figure 3(a)). The ZnO window is contacted at the periphery of the cell with a titanium/gold bilayer, ensuring that the cell is not shadowed by the electrical probes when contacted.…”