Photon and carrier management design for nonplanar thin-film copper indium gallium selenide photovoltaics

Abstract

Because it is commonly employed in experimental devices and in order to find an upper limit of device performance for the electrical parameters used, the optimum MgF 2 Anti-Reflection Coating (ARC) thickness was found by optimizing for photocurrent absorbed in the CIGS material. For planar and structured devices, the optimum thickness was 110 nm, while for the periodic device, the optimum was 166 nm. Figure S1a compares the 700 nm device with ARC (cp. Structured device with t=0 nm), the 1.7 µm device with ARC (cp. Structured device with t=1000 nm), and a planar 2.9 µm device with ARC. The 2.9 µm planar device with ARC was the optimal CIGS thickness found by parameterizing the CIGS thickness with the figure of merit being effciency in order to compare to the devices studied. Figure S1b shows that when adding the dielectric spacer layer to devices with optimized ARC, the thin planar device out-performs the optimized planar device in the case of perfect CIGS|SiO 2 interface passivation. The decreased reflection in the planar 700 nm device increases the current, and therefore efficiency, compared to Figure 4. The same is true of the other devices. The randomly textured device performs best of the three. These curves show the added benefit of dielectric layers, but also recognize that if suffciently low interface SRVs cannot be acheived, the optimum device will still be a thick planar device with ARC. Figure S1c shows the CIGS absorption when the ARC is applied. Compared to Figure 3c, the optimum ARC for planar and structured devices maximizes absorption near the peak of the photocurrent flux in the solar spectrum between 600-800 nm, with the optimum ARC coating being 110 nm thick. The periodic Figure S1: Devices with Anti-Reflection Coatings a) The JV curves of planar device with 110 nm MgF 2 ARC. The thicker optimized 2.9 µm device shows a minor improvement over the 1.7 µm textured device, corresponding to the planar equivalent thickness of a textured device with t=1000 nm b) The planar, periodic, and textured devices with a 190 nm dielectric layer at the back-contact and ARC outperform even the optimized planar device. Inset of a) and b) show the J-V parameters of the devices. c) the CIGS absorption spectra for the ARC coated devices in b).

CIGS photovoltaics: reviewing an evolving paradigm

“…This approach provided significant improvement in J SC from the BSR, but exhibited losses in V OC , showing less passivation effect than the best CIGS PERC results. The BSR EQE results exhibited J SC losses from Fabry-Pérot interference fringes, which could be eliminated by incorporating nonplanar photonic light scattering structures [4,238].…”