Improved Efficiency of a Large-Area Cu(In,Ga)Se₂ Solar Cell by a Nontoxic Hydrogen-Assisted Solid Se Vapor Selenization Process

A nontoxic hydrogen-assisted solid Se vapor selenization process (HASVS) technique to achieve a large-area (40 × 30 cm²) Cu­(In,Ga)­Se₂ (CIGS) solar panel with enhanced efficiencies from 7.1 to 10.8% (12.0% for active area) was demonstrated. The remarkable improvement of efficiency and fill factor comes from improved open circuit voltage (<i>V</i>_oc) and reduced dark current due to (1) decreased interface recombination raised from the formation of a widened buried homojunction with n-type Cd_Cu participation and (2) enhanced separation of electron and hole carriers resulting from the accumulation of Na atoms on the surface of the CIGS film. The effects of microstructural, compositional, and electrical characteristics with hydrogen-assisted Se vapor selenization, including interdiffusion of atoms and formation of buried homojunction, were examined in detail. This methodology can be also applied to CIS (CuInSe₂) thin film solar cells with enhanced efficiencies from 5.3% to 8.5% (9.4% for active area) and provides a facile approach to improve quality of CIGS and stimulate the nontoxic progress in the large scale CIGS PV industry

Large Scale and Orientation-Controllable Nanotip Structures on CuInS₂, Cu(In,Ga)S₂, CuInSe₂, and Cu(In,Ga)Se₂ by Low Energy Ion Beam Bombardment Process: Growth and Characterization

One-step facile methodology to create nanotip arrays on chalcopyrite materials (such as CuInS₂, Cu­(In,Ga)­S₂, CuInSe₂, and Cu­(In,Ga)­Se₂) via a low energy ion beam bombardment process has been demonstrated. The mechanism of formation for nanotip arrays has been proposed by sputtering yields of metals and reduction of metals induced by the ion beam bombardment process. The optical reflectance of these chalcopyrite nanotip arrays has been characterized by UV–vis spectrophotometer and the efficient light-trapping effect has been observed. Large scale (∼4′′) and high density (10¹⁰ tips/cm²) of chalcopyrite nanotip arrays have been obtained by using low ion energy (< 1 kV), short processing duration (< 30 min), and template-free. Besides, orientation and length of these chalcopyrite nanotip arrays are controllable. Our results can be the guide for other nanostructured materials fabrication by ion sputtering and are available for industrial production as well