Cu(InGa)Se₂ Solar Cell Efficiency Enhancement Using a Yb-Doped SnO_x Photon Converting Layer

Abstract

We report on the efficiency improvement of Cu(InGa)Se 2 (CIGS) based solar cells obtained upon coating the cell with a Yb-doped SnO x layer. This layer is deposited by reactive sputtering and serves as a photon down-shifting converter. The direct excitation of the SnO x host matrix with UV photons leads to a strong emission of near infrared photons from the Yb 3+ ions suggesting an efficient energy transfer from SnO x to the Yb 3+ ions. The deposition the Yb:SnO x films at higher temperatures results in an enhancement of the PL emission as well as in an improvement of the transport properties. The optimized films exhibit a transmittance around 80 % in the visible region, a resistivity of 6×10 −3 Ωcm and a mobility as high as 50.1 cm 2 /Vs. Such SnO x layers doped with 1.3 at. % of Yb were deposited at 100 • C on conventional CIGS based solar cells to replace the standard ZnO n-type conductive layer. The solar cells performances are noticeably improved. This is witnessed by a net gain of 10% of the external quantum efficiency (EQE) at 360 nm. The short-circuit current (J SC ) increased by about 0.56 mA/cm 2 while the fill factor reaches 64.4 %. As an overall result, the best solar cell exhibited a remarkable enhancement in efficiency of about 0.6 %. This improvement of the photovoltaic efficiency by a simple substitution of i-ZnO by Yb:SnO x for CIGS cells offers possible application to other solar cells. These results are encouraging towards enhancing the efficiency of solar cells at low cost which will contribute to the large deployment of clean energy.

Improving Ultraviolet Stability of Perovskite Solar Cells via Singlet Fission Down‐Conversion†

“…To date, quantum dots, semiconductor oxides, and rare earths‐based phosphors have been developed as DC materials in different solar cells. [ 29‐32 ] Wu et al . have tried to utilize UV light fully by spin‐coating NaYF 4 :Eu 3+ DC layer on the nonconducting side of FTO, which can convert UV light to visible light, thus resulting in an average PCE of 19.99% and maintaining more than 90% of its primitive PCE after 365 nm UV illumination for 10 h. [ 33 ] In addition to the use of rare‐earth DC materials, Song et al .…”

“…To date, quantum dots, semiconductor oxides, and rare earths-based phosphors have been developed as DC materials in different solar cells. [29][30][31][32] Wu et al have tried to utilize UV light fully by spin-coating NaYF 4 :Eu 3+ DC layer on the nonconducting side of FTO, which can convert UV light to visible light, thus resulting in an average PCE of 19.99% and maintaining more than 90% of its primitive PCE after 365 nm UV illumination for 10 h. [33] In addition to the use of rare-earth DC materials, Song et al have employed CsPbBr 3 inorganic perovskite nanocrystals as a photon downshifting layer to improve the PCE from 19.7% to 20.8% and retains over 90% of its initial PCE under UV illumination for 100 h. [34] According to the report, the DC-induced photovoltaic performance amelioration in photovoltaic devices depends on refractive indices and extinction coefficients of the DC materials. [35] Nevertheless, the aforementioned DC materials usually show deficiencies such as restricted light absorption ability, low fluorescence quantum yield, or poor stability under environmental conditions.…”

Exploiting the Optical Limits of Thin‐Film Solar Cells: A Review on Light Management Strategies in Cu(In,Ga)Se2

“…[226,[229][230][231][232][233][234] In addition, luminescent layers have also been implemented between the buffer and window, either by doping a TCO with luminescent compounds or through the deposition of quantum dots (QDs). [235][236][237][238] In this placement, the luminescent layer can have a harmful effect on the solar cell FF value, which has an impact on the overall solar cell efficiency. [237,238] Therefore, the integration into an encapsulation polymer matrix appears more advantageous, as an optimization independent from the solar cell technology can be done.…”

Application of Quantum Dot Down-Conversion Layer in Thin-Film Solar Cells to Increase Short-Wavelength Spectral Response

“…13,14 On the other hand, there have been studies of applying downconversion layer using materials such as ZnO nanoparticle, organic dye, and Yb-doped SnO x . [15][16][17] The materials used as down-conversion layer absorb the light in the short-wavelength region and convert into light in the long-wavelength region. [18][19][20][21] These layers allow the passage of light, which is otherwise dissipated owing to absorption loss, through the buffer and TCO layers to reach the absorber layer.…”