Strain Mapping of CdTe Grains in Photovoltaic Devices

Abstract

Strain within grains and at grain boundaries in polycrystalline thin-film absorber layers limits the overall performance due to higher defect concentrations and band fluctuations. However, the nanoscale strain distribution in operational devices is not easily accessible using standard methods. X-ray nanodiffraction offers the unique possibility to evaluate the strain or lattice spacing at nanoscale resolution. Furthermore, the combination of nanodiffraction with additional techniques in the framework of multi-modal scanning X-ray microscopy enables the direct correlation of the strain with material and device parameters such as the elemental distribution or local performance. This approach was applied for the investigation of the strain distribution in CdTe grains in fully operational photovoltaic solar cells. It was found that the lattice spacing in the (111) direction remains fairly constant in the grain cores but systematically decreases at the grain boundaries. The lower strain at grain boundaries is accompanied by an increase of the total tilt. These observations are both compatible with the inhomogeneous incorporation of smaller atoms into the lattice, and local stress induced by neighboring grains.

X‐Ray Microscopy of Halide Perovskites: Techniques, Applications, and Prospects

“…Furthermore, in situ or operando beam induced current studies are readily achievable using X-ray nanoprobes. For example, XBIC is often utilized in multimodal microscopy, enabling the correlation of the electronic XBIC signal with compositional (XRF) [42,119] or structural/strain (XRD) information, [120,121] providing further insights on the root cause of detrimental/enhanced electronic performance. The primary advantage of XEOL with respect to XBIC is its ability to be carried out on the material level, without device contacts, similar to cathodoluminescence.…”

“…Combining SXDM with XBIC or other in situ optoelectronic measurements would aid understanding the role of strain, orientation and secondary phases under such conditions, as has recently been shown in CIGS and CdTe solar cells. [120,121] 3.5 X-ray Ptychography as a Path to Super-Resolution X-ray ptychography brings together scanning transmission imaging and coherent diffraction techniques to enable X-ray imaging over extended objects at single-nanometer-level resolution without the need for a perfect lens, thus overcoming a major obstacle in today's X-ray imaging hardware. In place of such a lens, a computational algorithm is used to reconstruct real space images from captured diffraction patterns.…”

Four-Fold Multi-Modal X-ray Microscopy Measurements of a Cu(In,Ga)Se2 Solar Cell

“…So far, scanning hard X-ray microscopy of solar cells has been used predominantly for the correlation of the elemental distribution with the electrical performance [ 12 , 13 , 14 ]. Only recently, measurements of the intra-grain strain have been included [ 15 , 16 , 17 ].…”

Micromachined Silicon Platform for Precise Assembly of 2D Multilayer Laue Lenses for High-Resolution X-ray Microscopy

“…X-ray microscopy is a powerful characterization tool applied in many scientific fields, such as materials science, biology, environmental science, and energy research [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 ]. Among different types of X-ray focusing optics [ 9 , 10 , 11 , 12 , 13 , 14 , 15 ], multilayer Laue lenses (MLLs) have been proposed and used for high-efficiency nanofocusing in the hard X-ray regime [ 9 , 16 , 17 ].…”