Citrate-Capped Cu₁₁In₉ Nanoparticles and Its Use for Thin-Film Manufacturing of CIS Solar Cells

Abstract

Intermetallic Cu 11 In 9 nanoparticles with diameters of 10−30 nm were prepared via a facile, easy-to-scale-up polyol-mediated synthesis. Citrate is used as surface-capping and guarantees for efficient stabilization of the Cu 11 In 9 nanoparticles against oxidation in suspension and of powder samples in contact to air. Moreover, the citrate-capping suppresses particle-to-particle agglomeration and allows to prepare high-quality suspensions and even to redisperse Cu 11 In 9 powder samples. The latter is essential to obtain stable inks with precise element composition that can be directly used for thin-film deposition via doctor blading. Based on as-deposited thin-films, high-quality CuInSe 2 (CIS) solar cells with power-conversion efficiencies up to 7% were produced by a simple and low-cost, vacuum-free selenization process without the need of additional reducing or sintering processes. Cu 11 In 9 nanoparticles and CIS thin-films as well as the completed solar cells were characterized by various independent analytical tools, including electron microscopy (SEM/STEM), DLS, FT-IR spectroscopy, EDX, XFA, XRD, and SIMS/SNMS.

Low temperature formation of CuIn 1−x Ga x Se 2 solar cell absorbers by all printed multiple species nanoparticulate Se + Cu–In + Cu–Ga precursors

“…Absorber layers also processed from Cu-In nanoparticles by Kind et al [16] or Lim et al [17] but under Se(g) atmosphere, show a dense CISe layer on top of a porous CISe layer similar to the one presented in this work. The densification can be attributed to a permanently saturated Se atmosphere surrounding the precursor particles near the surface of the precursor.…”

“…5). Ex-situ XRD reveals the phases of the two species nanoparticulate precursor which are hexagonal Se (pdf #00-006-0362), Cu 11 In 9 (pdf #00-041-0883), Cu 16 In 9 (pdf #00-041-0883) and CuIn 2 (simulated reflection table based on the results of Keppner et al [30]). As metallic materials cannot be observed by Raman measurements only selenium is observable.…”

“…The most prominent techniques are based on deposition of material from solution [6][7][8] or deposition of nanoparticles, while there is a difference in the type of used nanoparticles. One has to distinguish between chalcopyrite nanoparticles which consist of a well-formed Cu(In 1 − x Ga x )(Se 1 − y S y ) phase [9][10][11][12][13] and precursor nanoparticles which can be a mixture of either Cu-Se and In-Se nanoparticles [14] or metallic Cu-In nanoparticles which are selenised after deposition by annealing under highly toxic H 2 Se or selenium atmosphere [15][16][17].…”

All Solution‐Processed Chalcogenide Solar Cells – from Single Functional Layers Towards a 13.8% Efficient CIGS Device

“…[ 30 ] Non-vacuum deposition methods have been intensively investigated as refl ected in several reviews, [ 9,[31][32][33] and among them the most promising are two-step approaches where a precursor layer is coated from solutions, nanoparticle dispersions, or by ED followed by an annealing step under S, Se and/or H 2 Se atmosphere. The nanoparticle route has achieved the highest effi ciencies to date of up to 17.12% reported by company Nanosolar Inc. [ 34 ] Other nanoparticle routes exhibit lower conversion effi ciencies of devices [35][36][37] and often employ H 2 , H 2 Se, or H 2 S gasses requiring special safety measures. [ 38 ] True solution inks naturally overcome the need for particle pre-fabrication and stabilization, and thus present an up-scalable and less sophisticated option.…”

Se-containing inks for the formation of CuInSe2 films without gas-phase selenization

“…In case of the former, various material classes have been tested, including metals, metal oxides and metal sulfides and selenides, either as binary, ternary or quaternary compounds [10][11][12]. In almost all cases, the transformation of the precursor film into the eventual absorber layer involves an annealing step in a selenium-containing atmosphere.…”