Plasmonically Enhanced Spectral Upconversion for Improved Performance of GaAs Solar Cells under Nonconcentrated Solar Illumination

Abstract

Spectral upconversion has the potential to compensate for sub-bandgap transparency of single-junction solar cells. Here a composite module of GaAs solar cells is presented that can improve their one-Sun photovoltaic performance by capturing long-wavelength photons below the bandgap via plasmonically enhanced spectral upconversion. Ultrathin, microscale GaAs solar cells released from the growth wafer and etched with a bottom contact layer are printed on a polymeric waveguide containing NaYF 4 :Er 3+ , Yb 3+ upconversion nanocrystals (UCNC), coated on a plasmonic reflector composed of hole-post hybrid silver nanostructure. The photovoltaic efficiency of GaAs microcells on a UCNC-incorporated plasmonic substrate is increased by ∼6.4% (relative) and ∼11.8% (relative), respectively, compared to those on a nanostructured silver reflector without UCNC and on a plain silver reflector with UCNC, owing to the combined effects of local electric-field amplification to enhance the absorption of UCNC, augmented upconverted emission via coupling into radiative modes, as well as waveguided photon concentration.

Optical Management with Nanoparticles for a Light Conversion Efficiency Enhancement in Inorganic γ-CsPbI3 Solar Cells

“…Importantly, the surface roughness of the films slightly increased (from 4.81 to 8.10 nm) with an increasing UCNP concentration from 0 to 5 mg/mL. Meanwhile, the reflection of light at an interface between two different media depends on the refractive index of the materials. , Hence, the synergistic effect of the rougher surface and the changed refractive index of UCNPs/PTAA in the heterogeneous UCNPs/PTAA coating could largely enhance light backscattering and reabsorption. ,− …”

Strategically Manipulated Polymer Solar Cells to Incorporate Plasmonically Enhanced Spectral Upconversion Backplane

“…Meanwhile, it needs to be mentioned that the enhanced local field of the surface plasmon resonance cannot consistently affect such thick (≈1 µm) UCNP layer, even with the deep‐patterned (≈320 nm) Ag nanohole as a plasmonic substrate (Figure S5, Supporting Information). Despite less improvement of upconversion emission intensity (≈10 2 times) compared to the previous reports using thin (≈100 nm) UCNP layers, [ 23–25 ] a higher level of the upconversion luminescence can be expected by the remaining plasmonic evanescent field. The marked absorption property of the designed upconversion backplane in the entire wavelength range can hardly impinge on the cell performance due to the reflection because the incident solar photons irrelevant to the upconversion process are reflected back at the ST electrode before reaching the backplane.…”

“…As a high level of the upconversion quantum yield is essential for accomplishing the meaningful effect on the integrated PV cells, [ 34–36 ] the numerical modeling to find optimal geometries of Ag nanohole array that offers the plasmonic field amplification to UCNPs was conducted with the finite‐difference time‐domain (FDTD) method. In this modeling, a surrounding medium of the Ag nanohole was assumed to be a homogeneous lossless (i.e., extinction coefficient; k = 0) material with an identical refractive index ( n = 1.49) to that of UCNPs [ 23–25 ] for simplicity. A taper angle of nanoholes was set to 5° (i.e., ( D top /2 – D bot /2)/ h = tan 5°) in consideration of the experimental observation.…”

“…[ 21,22 ] Indeed, enhancement of the PV performance had been reported for several PV classes including silicon and III‐V solar cells. [ 23–26 ] In contrast to these successful demonstrations, attempts to obtain the high PV performance at a class of optically ultrathin solar cells (e.g., PSCs, perovskite solar cells) by incorporating the upconversion systems have been unexpectedly frustrated, because the pre‐existing rear‐side reflector of metallic electrode, that greatly augments the optical path length and therefore the amount of solar photon absorption in the photoactive layer, should be removed in order to allow the penetration of the incident sub‐bandgap photons for excitation of the upconversion medium behind the cells, together with the consequently upconverted above‐bandgap photons. This means that a level of the photocurrent needs to be compromised for the effective photonic interaction between the photoactive layer and upconversion medium.…”

Opportunities from Doping of Non‐Critical Metal Oxides in Last Generation Light‐Conversion Devices

“…Significant examples are the combination of: i) broadband sensitizers and RE 3+ ions [170] (Figure 11a); ii) downshifting and scattering when phosphors are dispersed in the DSSCs or PSCs active layer; [194] iii) downshifting coupled to antireflection when phosphors are deposited on the front surface of the cell [333] (Figure 11b); iv) spectral conversion enhanced by plasmonic structures. [334,335]…”