Real-Time Optimization of Anti-Reflective Coatings for CIGS Solar Cells

Abstract

A new method combining in-situ real-time spectroscopic ellipsometry and optical modeling to optimize the thickness of an anti-reflective (AR) coating for Cu(In,Ga)Se2 (CIGS) solar cells is described and applied directly to fabricate devices. The model is based on transfer matrix theory with input from the accurate measurement of complex dielectric function spectra and thickness of each layer in the solar cell by spectroscopic ellipsometry. The AR coating thickness is optimized in real time to optically enhance device performance with varying thickness and properties of the constituent layers. Among the parameters studied, we notably demonstrate how changes in thickness of the CIGS absorber layer, buffer layers, and transparent contact layer of higher performance solar cells affect the optimized AR coating thickness. An increase in the device performance of up to 6% with the optimized AR layer is demonstrated, emphasizing the importance of designing the AR coating based on the properties of the device structure.

Lowering Cost Approach for CIGS-Based Solar Cell Through Optimizing Band Gap Profile and Doping of Stacked Active Layers─SCAPS Modeling

“…Each of the innovative solutions is designed to limit the optical losses to a specific area; however, they can be combined to maximize the PCE of the cell. The substitution of conventional metal contacts with interdigitate contacts and the use of an antireflective layer on top of the window layer improve the transmission of the light to the active layer. , Other changes in the basic structure relate to the use of new materials as a window layer, buffer layer, or electron back reflector (EBR). − The recent study by Olivier et al details many other light management strategies applicable to CIGS-based ultrathin cells as well as their limitations.…”

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

“…[106] To find the AR layer optimal thickness value, all the inactive layers that act as an obstacle between air and CIGS have to be considered. [107,108] Rajan et al demonstrated the dependence of the optimal MgF 2 thickness value on the individual solar cell layers' thickness variation: CIGS absorber (500-2500 nm), the CdS buffer (20-90 nm), and the AZO window (150-300 nm). [108] To do so, the authors used a transfer matrix theory optical model combined with in situ real-time spectroscopic ellipsometry measurements, while depositing the AR layer, to measure the unpolarized reflection as a function of the AR thickness.…”

“…[107,108] Rajan et al demonstrated the dependence of the optimal MgF 2 thickness value on the individual solar cell layers' thickness variation: CIGS absorber (500-2500 nm), the CdS buffer (20-90 nm), and the AZO window (150-300 nm). [108] To do so, the authors used a transfer matrix theory optical model combined with in situ real-time spectroscopic ellipsometry measurements, while depositing the AR layer, to measure the unpolarized reflection as a function of the AR thickness. With such an approach, both theoretical models and experimental results demonstrated that as the individual solar cell layers thickness values are modified, the optimum MgF 2 thickness has to be adjusted to achieve a minimum reflectance.…”

Fabrication of CZTS Solar Cells Using Electrodeposition Techniques

“…In some instances, an anti-reflection layer is also deposited, which increases the amount of light that reaches the absorber layer and therefore increases the device efficiency. The layer is ~100 nm thick [146,147] and magnesium fluoride (MgF2), aluminium oxide (Al2O3) and cerium fluoride (CeF3), for example, can be used [148]. One method of deposition is via electron beam evaporation [146,147],…”

“…The layer is ~100 nm thick [146,147] and magnesium fluoride (MgF2), aluminium oxide (Al2O3) and cerium fluoride (CeF3), for example, can be used [148]. One method of deposition is via electron beam evaporation [146,147],…”