Facile Silver-Incorporated Method of Tuning the Back Gradient of Cu(In,Ga)Se₂ Films

Abstract

An appropriate gallium (Ga) back gradient in Cu(In,Ga)Se 2 (CIGS) films is vital to achieve solar cells with good device performances. As a steeper Ga back gradient can induce an enhanced electric potential variation or affinity (conduction band) variation, it can make the electrons stay away from the rear contact. In addition, significant lattice distortions can be found at the back gradient of CIGS films, which increases carrier recombination and impedes carrier transport. In this study, by employing an Ag−Se precursor before the CIGS process, silver (Ag) is purposefully doped to the back gradient of CIGS films to reduce the lattice distortions. A comparison of the structure and device characteristics of CIGS films with different Ag−Se deposition durations is carried out. This study suggests that the addition of an Ag−Se precursor can enhance the quality of the CIGS film and modify the back gradient as well as enhance recrystallization, which improves the device performance of solar cells. Simultaneously, the enhanced grain sizes achieved by the Ag-treated process are helpful for the improvement of carrier mobility and the reduction of boundary recombination in CIGS films. Furthermore, the accumulation of indium caused by the Ag−Se precursor film in the first stage should contribute to the formation of a modified back gradient. This work offers an easy route for the control of the Ga back gradient in CIGS thin film solar cells.

Band Gap Engineering in Quadruple-Layered Sillén–Aurivillius Perovskite Oxychlorides Bi7Fe2Ti2O17X (X = Cl, Br, I) for Enhanced Photocatalytic Performance

“…It is observed also that, the order of light response intensities is BFTOC > BFTOB > BFTOI, which can be ascribed to the sub-band gap absorption of powder materials. As we know, the significant sub-band gap absorption of films is indicative of the presence of the secondary phases or the band tailing [44][45][46][47]. This observation suggests the BFTOC powder has the lowest defect concentrations and photogenerated carrier recombination compared with the two other samples, which should be the reason for the highest performance of CO2 reduction for BFTOC sample, as is consistent with the SEM results.…”

Pulse Selenization in Cu(In,Ga)Se2 Solar Cells: A Promising Approach to Achieve High Efficiency by Electrodeposition

“…It exhibits that the grains at the top of sample # 0 are larger than that near the Mo layer. The main reason for this appearance is that the reaction rates between In and Se are faster than those between Ga and Se, resulting in the accumulation of Ga and the formation of fine grains near the back contact during the selenization process . In addition, the crevices appear at the Mo/CIGS interface, indicating that the electrodeposited CIGS film has poor adhesion on the Mo layer.…”

Organic Passivation of Deep Defects in Cu(In,Ga)Se 2 Film for Geometry-Simplified Compound Solar Cells

“…Those voids are comment for the CIGS processes, especially for the electrodeposition method [ 43 ]; more easily formed voids allow us to expect the better passivation effect for electrodeposited CIGS solar cells. Note that high concentration of Mo at front interface is a measurement artifact that may be caused by the impurities with the same molecular weight with Mo, which can also be found elsewhere [ 44 , 45 ].…”