(447f) Solar Cells with Graded Composition Absorber Layers Enabled by CIGS Nanocrystal-Based “Inks” | AIChE

(447f) Solar Cells with Graded Composition Absorber Layers Enabled by CIGS Nanocrystal-Based “Inks”

Authors 

Goodfellow, B. W. - Presenter, University of Texas at Austin
Akhavan, V. A. - Presenter, University of Texas at Austin


Copper Indium Gallium Selenide (CIGS) is one of the most promising absorber materials for single-junction solar cells due to its demonstrated efficiency and tunable bandgap. However, conventional CIGS deposition by vacuum techniques is costly and control of the stoichiometry on large-area substrates is a challenge. In an effort to produce ultra-low cost photovoltaic (PV) devices, we have developed Cu(In1-xGax)Se2 (CIGS) nanocrystal-based ?inks? that can be spray-deposited and have fabricated PV devices with power conversion efficiencies of 1.5% under AM1.5 illumination on both standard glass and flexible plastic substrates. One interesting feature of the nanocrystal inks is that they can be deposited to yield controlled composition gradients in the absorber layer. The Ga content in the nanocrystals?and thus the bandgap and band offsets of the materials?can be easily tuned in the nanocrystal synthesis. By synthesizing an array of CIGS nanocrystal-based ?inks? with varying gallium content, we can fabricate devices with absorber layers with have specific bandgap gradings. These absorber layers are designed to improve minority carrier drift and the overall power conversion efficiency of the solar cell. Graded-bandgap CIGS absorber layers are very difficult to fabricate using conventional vacuum-based deposition schemes. The fabrication and performance of graded-composition, sprayed CIGS nanocrystal PV devices will be presented.