Review on the effects due to alkali metals on copper–indium–gallium–selenide solar cells

Insights into the Effects of RbF‐Post‐Deposition Treatments on the Absorber Surface of High Efficiency Cu(In,Ga)Se2 Solar Cells and Development of Analytical and Machine Learning Process Monitoring Methodologies Based on Combinatorial Analysis

“…The QY rise is explained by the increased amount of radiative recombination, which can be related to an increased concentration of beneficial point defects (the defects that contribute in radiative recombination) or to a decrease of the concentration of detrimental point defects (the defects that contribute in non‐radiative recombination). Previously, the increase of the relative PL QY due to PDT was associated with the passivation of donor‐like defects (V Se and In Cu ) that contribute in the appearance of deep donor levels, [ 60–62 ] and correlates with the decrease of the concentration of detrimental defects mentioned above. However, the existence of the deep donor levels does not correlate with the high efficiency of the reference device in this work (close to 18%) which is higher than those reported in refs.…”

Extrinsic Doping of Ink‐Based Cu(In,Ga)(S,Se)2‐Absorbers for Photovoltaic Applications

“…Vacuum processing methods such as co‐evaporation and sequential processes are commonly used to fabricate absorbers for high‐efficiency PV devices. [ 51,59 ] In co‐evaporation methods, the chalcogenide absorber layers are crystallized during growth with excess chalcogen vapor pressure (e.g., Se/S) at high temperatures (>500 °C). [ 38 ] Depending on the number of elemental flux and/or temperature stages used during the growth process, co‐evaporation methods are categorized into single stage, two‐stage, or three‐stage processes.…”

“…[ 116,118,206 ] These results cemented the importance of adding sodium to the absorber layer and spurred research on developing new incorporation strategies. [ 207 ] Over the years, several contradictory results relating to the effect of Na addition to the CIGSSe absorber appeared including i) grain size (increased, [ 204,208,209 ] decreased, [ 197,210–213 ] no relation, [ 28,214 ] ) ii) preferentially oriented growth (promoted (220/204) growth, [ 215 ] promoted (112) growth [ 216,217 ] ), iii) decreased concentration of traps or deep levels, [ 196,218 ] iv) GB passivation [ 28,104,214,219–221 ] ), and v) p‐type conductivity (increased, [ 28,115,222 ] decreased, [ 51,223,224 ] ). The differences in findings can be related to the vast differences in absorber composition and growth conditions.…”

“…[ 84,244 ] A wide range of compounds have been studied in ink‐based routes (e.g., Na 2 S, [ 208 ] KF, [ 245 ] sodium citrate, [ 33 ] KCl, [ 138 ] and Sb 2 S 3 [ 246 ] ) as opposed to the predominantly used alkali halide salts (e.g., Na 2 S, NaCl, Na 2 Se, NaF, KF, RbF, and CsF) in vacuum processing. [ 51,223,224 ] The following sections further expand on the PV applications of the most commonly used dopants (e.g., Na, K, Sb, Bi) in MI‐based CIGSSe/CISSe PV, and the advancements achieved by these approaches. Notably, unless specifically mentioned, all devices mentioned in the subsequent sections utilize an SLG substrate, without a barrier layer.…”

“…[50] The natural diffusion of sodium and other alkalis from SLG substrates is difficult to precisely control, and hence, not preferred for large-scale module manufacturing. [35,51] Consequently, alkali-free glass substrates are often employed to study the explicit influence of an alkali metal added to the film in controlled amounts. Corning has produced a variety of alkalifree glasses such as Corning 7059 (CTE ≈ 4.0 × 10 −6 K −1 ) [24,52] and Corning EAGLE XG (CTE ≈ 3.0 × 10 −6 K −1 ) [53] glasses, that are compatible with CIGSSe PV applications.…”