Effects of Ammonia‐Induced Surface Modification of Cu(In,Ga)Se₂ on High‐Efficiency Zn(O,S)‐Based Cu(In,Ga)Se₂ Solar Cells

Abstract

Post‐treatment of Cu(In,Ga)Se2 (CIGS) surfaces, as an efficient way to improve the performance of CIGS solar cells, has received increasing attention in recent years. To alleviate the limitations of the as‐grown CIGS thin films, such as oxidation, Na accumulation, and microstructure of CIGS surface, ammonia (NH3) etching solution was introduced to post‐treat the CIGS surface to improve its quality in this study. To investigate the mechanisms of NH3 etching effects on the CIGS surfaces and the resulted devices, a series of NH3 solution treatments, of different concentrations, on CIGS films is carried out and the resulted surfaces and devices are carefully examined. It is demonstrated that proper concentration of NH3 solution could not only result in a new microstructure between CIGS and Zn(O,S) thin films but also improve the performance of the Zn(O,S) based CIGS solar cells, especially in terms of the device fill factor. As a result, a Zn(O, S) based CIGS solar cell with a conversion efficiency of over 20% is obtained with application of NH3 treatment together with MgF2 anti‐reflective coating. Furthermore, it is found that NH3 treatment could effectively reduce the undesired light soaking effect, which often appears in the Zn(O,S) based CIGS solar cells.

Silver Surface Treatment of Cu(In,Ga)Se2 (CIGS) Thin Film: A New Passivation Process for the CdS/CIGS Heterojunction Interface

“…Figure 4b–e demonstrates the evolution behaviors of the selected peaks of Ga, In, Ag, and Cu elements by Ag on the surface of the CIGS film. [ 42 ] Although there is no significant difference in binding energy for all elements, the intensity of the selected peaks has an obvious difference.…”

Effects of Laser‐Scribed Mo Groove Shape on Highly Efficient Zn(O,S)‐Based Cu(In,Ga)Se2 Solar Modules

“…Depending on the technology of CIGS thin‐film solar cells, they may include CdS film or Zn(O,S) film as the buffer layer . In this work, Zn(O,S) was used as the buffer layer, and the corresponding structure is shown in Figure a as glass/Mo (≈1 μm)/CIGS (≈2.5 μm)/Zn(O,S) (≈30 nm)/TCO (ZnMgO/Al:ZnO) (≈600 nm).…”

“…The Zn(O,S) buffer layers were deposited by chemical bath deposition method. More details can be found in previous works . For modules, three scribing steps were introduced in this work, namely, after deposition of Mo for P1, of ZnMgO for P2, and of Al:ZnO for P3.…”

“…Thin‐film solar cells are promising for reduction of production cost due to the effective use of raw materials . Cu(In,Ga)Se 2 (CIGS), as one of the most successful photovoltaic (PV) materials, has been widely investigated in the past 30 years in both small‐area cells and large‐area modules . Recently, the new world record efficiency of Cu(In,Ga)(Se,S) 2 (CIGSSe) thin‐film solar cells has already reached 23.35% .…”

Giant Voc Boost of Low‐Temperature Annealed Cu(In,Ga)Se2 with Sputtered Zn(O,S) Buffers

“…The superior performance of CIGS cells obtained with buffers deposited by CBD has been ascribed to the formation of buried p–n junctions, resulting from the enhanced diffusivity of the ions in the liquid phase . This is supported by the fact that postannealing treatments of the complete solar cells can lead to further performance enhancements, even with CBD‐grown ZnS and Zn(O,S) buffers …”