Heterojunction solar cells produced by porous silicon layer transfer technology

Fabrication of seeded substrates for layer transferrable silicon films

“…Among kinds of kerfless methods, [7][8][9][10][11][12] the technique based on double porous silicon has been most developed. [13][14][15][16] Up to now, the solar cells with an efficiency of 23% have been achieved and flexible solar cells with an efficiency of 21.2% have also been successfully made from this porous silicon kerfless technique. [17,18] However, this technique still faces some intractable problems for high crystalline quality and low cost, such as metal contaminants from the electrolyte during the formation of the porous bilayer, surface buckling during the recrystallization of the upper porous layer, and limited reuse of the mother substrates due to the inevitable re-building process of the porous bilayer, etc.…”

Simulation and Control of Porosity in a Three-Dimensional Thin-Film Solar Cell

“…Optimizing the light trapping process is one of the major aspects to improve the solar cell conversion efficiency and is one of the central research aspects nowadays (see, for example, refs and ). It has been found in previous research studies that surface morphology, which includes surface roughness and slope, at each film interface strongly affects the light trapping process, − and the use of porous silicon (PS) film as an intermediate layer between the substrate and the thin silicon film can improve the substrate backside reflectance and prevent the material contamination. − Specifically, it has been shown that a single porous silicon layer could serve as a seeding layer and is necessary for a sufficient light reflection. ,, Moreover, at the same time, this porous silicon layer could be a guttering barrier preventing impurity diffusion from the low-cost substrate into the active silicon layer . Research also indicates that porous silicon can reduce solar cell optical losses from 37% to 8% and increase a short-circuit current by 25% and open-circuit voltage by 20 mV .…”

In situ annealing and high-rate silicon epitaxy on porous silicon by mesoplasma process

“…22,23) It can also be understood, as has been reported in the reference, that porous Si reorganization occurs through vacancy diffusion processes driven by a vacancy concentration gradient between the pore (or voids) and its surrounding lattice. 5) However, unlike the conventional process that forms a smooth surface free of open voids, 6,24) the porous Si after Ar-H 2 mesoplasma annealing shows a rough surface with large voids, as shown in Fig. 1(d).…”

“…This structure is basically similar to that obtained by conventional annealing at H 2 ambient for 30 min at 1050°C. 6,9) Moreover, note that the void size decreases with depth, i.e., the voids closer to the high-porosity layer are much smaller than those on top. This is consistent with that shown in Ref.…”

“…[5][6][7][8][9] In this process, the porous Si is annealed at hydrogen ambient for more than 30 min at a temperature of ∼1100°C to close the voids on the surface, and the epitaxial Si films are grown at a rate of several 10 nm=s by TCVD from an equilibrium process. [6][7][8][9] Recently, it has been demonstrated that the mesoplasma CVD (MPCVD) can be used for epitaxial Si film deposition with an ultrahigh rate of ∼700 nm=s (from SiHCl 3 ) owing to its unique deposition process, including a high degree of nonequilibrium process, the formation of nanoclusters as deposition precursors, and the instantaneous and simultaneous migration and rearrangement of Si atoms as the clusters impinge on the substrate surface, resulting in high-rate Si epitaxy. [10][11][12][13][14][15][16] In this process, highrate and large-area Si epitaxy can be obtained by moving the substrate.…”