Ultrawide Spectral Response of CIGS Solar Cells Integrated with Luminescent Down-Shifting Quantum Dots

Abstract

Conventional Cu(In,Ga)Se (CIGS) solar cells exhibit poor spectral response due to parasitic light absorption in the window and buffer layers at the short wavelength range between 300 and 520 nm. In this study, the CdSe/CdZnS core/shell quantum dots (QDs) acting as a luminescent down-shifting (LDS) layer were inserted between the MgF antireflection coating and the window layer of the CIGS solar cell to improve light harvesting in the short wavelength range. The LDS layer absorbs photons in the short wavelength range and re-emits photons in the 609 nm range, which are transmitted through the window and buffer layer and absorbed in the CIGS layer. The average external quantum efficiency in the parasitic light absorption region (300-520 nm) was enhanced by 51%. The resulting short circuit current density of 34.04 mA/cm and power conversion efficiency of 14.29% of the CIGS solar cell with the CdSe/CdZnS QDs were improved by 4.35 and 3.85%, respectively, compared with those of the conventional solar cells without QDs.

One‐Pot Gram‐Scale, Eco‐Friendly, and Cost‐Effective Synthesis of CuGaS2/ZnS Nanocrystals as Efficient UV‐Harvesting Down‐Converter for Photovoltaics

“…Motivated by these purposes and attracted by their excellent optical properties, Cd‐based core/shell QDs, such as CdSe/CdS,[13c,15] CdSe/CdZnS, CdSe/ZnS,[11b] and Cd 0.5 Zn 0.5 S/ZnS[13b,17] QDs have been used recently as EDS layers. However, the relying on the Cd‐based QDs in commercial solar cells has been limited due to two main reasons; the toxicity of Cd metal ions and the self‐reabsorption losses within their QDs.…”

“…[10] These losses are mostly caused by the energy difference between the incident UV photons (>3.2 eV) and bandgap of PV cells (1.0-1.6 eV). [1d,14] For the abovementioned reasons, the concept of the EDS-QD layer was proposed for solar energy conversion for both increasing the efficiency and lessening the cost.Motivated by these purposes and attracted by their excellent optical properties, Cd-based core/shell QDs, such as CdSe/ CdS, [13c,15] CdSe/CdZnS, [16] CdSe/ZnS, [11b] and Cd 0.5 Zn 0.5 S/ ZnS [13b,17] QDs have been used recently as EDS layers. [12] One of the most promising approaches to overcome these limitations is to implement the surfaces of PV devices with an energydownshift quantum-dot (EDS-QD) layer to harvest the wasted UV photons and reemit them at visible wavelengths absorbed more efficiently by PV cells.…”

Improving Ultraviolet Responses in Cu2ZnSn(S,Se)4 Thin-Film Solar Cells Using Quantum Dot-Based Luminescent Down-Shifting Layer

“…However, rapidly drying the solvent at 80 • C caused uneven distribution of the QDs in the centers of the samples. To reduce the amount of QDs required, techniques such as the masking method need to be applied [16], so we believe that there is still room for improvement. To verify the effects of the MgF 2 capping layer protecting the QDs from oxygen and moisture, we conducted comparative analyses on the uncapped and capped CZTSSe solar cells (Figure 6).…”

“…Furthermore, solar cells made of Cu 2 ZnSn(S,Se) 4 (CZTSSe) or Cu(In,Ga)(S,Se) 2 (CIGS) mainly use CdS as the buffer layer, which has the disadvantage of absorbing ultraviolet (UV) light [ 1 , 2 , 3 ]. To solve this narrow absorption band problem, researchers are studying luminescent down-shifting (LDS) layers that can widen the absorption bands via simpler methods than multijunction or tandem solar cells [ 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 ]. The quantum dot (QD)-based LDS layer utilizes the properties of QDs that absorb light of short wavelengths and emit light with large wavelengths.…”

Cu(In,Ga)Se2 Solar Cells Integrated with Subwavelength Structured Cover Glass Fabricated by One-Step Self-Masked Etching

“…Molybdenum was sputtered on soda lime glass as a back contact layer. A p-type CIGS absorber layer with a thickness of 2 μm was prepared using a three-stage co-evaporation method [ 29 ]. Afterwards, an n-type CdS buffer layer was grown on the CIGS layer by chemical bath deposition.…”