Chlorine activated stacking fault removal mechanism in thin film CdTe solar cells: the missing piece

Abstract

The conversion efficiency of as-deposited, CdTe solar cells is poor and typically less than 5%. A CdCl2 activation treatment increases this to up to 22%. Studies have shown that stacking faults (SFs) are removed and the grain boundaries (GBs) are decorated with chlorine. Thus, SF removal and device efficiency are strongly correlated but whether this is direct or indirect has not been established. Here we explain the passivation responsible for the increase in efficiency but also crucially elucidate the associated SF removal mechanism. The effect of chlorine on a model system containing a SF and two GBs is investigated using density functional theory. The proposed SF removal mechanisms are feasible at the 400 ∘C treatment temperature. It is concluded that the efficiency increase is due to electronic effects in the GBs while SF removal is a by-product of the saturation of the GB with chlorine but is a key signal that sufficient chlorine is present for passivation to occur.

Codesigning Alloy Compositions of CdSeyTe1−y Absorbers and MgxZn1−xO Contacts to Increase Solar Cell Efficiency

“…At the same time, it indicates that this must be done within other constraints such as avoiding overly large barriers that can impede overall performance. Future studies can use combinatorial methods to explore mechanisms and further enhance efficiency by optimizing additional parameters such as Cl heat treatment [ 36 ] and back‐contact Cu doping for the best absorber–contact combination space.…”

Next-generation applications for integrated perovskite solar cells

“…Cadmium-telluride (CdTe) solar cells are currently among the most successful low-cost thin-film technology in the PV market with an installed capacity of over 25 GW 63 . The certified record PCE of a CdTe cell is 22.1% 4 .…”

Anode interfacial modification for non‐fullerene polymer solar cells: Recent advances and prospects

“…Several types of solar cells such as Si‐based solar cells, cadmium telluride (CdTe), and cadmium indium gallium selenide (CIGS) are commercially available. Although these solar cells exhibit a power conversion efficiency (PCE) of over 24% with an average lifetime of 25 years; however, the processing cost, and utilization of rare and hazardous elements restrain their application 1–6 . Interestingly, polymer solar cells (PSCs) offer several advantages such as light‐weight, low‐cost, solution processability, and large area roll‐to‐roll (R2R) fabrication on a plastic substrate 7–10 …”

“…exhibit a power conversion efficiency (PCE) of over 24% with an average lifetime of 25 years; however, the processing cost, and utilization of rare and hazardous elements restrain their application. [1][2][3][4][5][6] Interestingly, polymer solar cells (PSCs) offer several advantages such as light-weight, low-cost, solution processability, and large area roll-to-roll (R2R) fabrication on a plastic substrate. [7][8][9][10] PSCs are composed of a photoactive layer commonly called bulk heterojunction (BHJ) sandwiched between cathode interlayer (CIL) and anode interlayer (AIL).…”