1. Meeting 2014-October WP1 INL :

2. 2 -1. Simulation for Laser Interference Lithography sample (PI32) -2. Possible alternative: patterning of the front electrode only, not of the active layer -3. Double side patterning: back side patterning at ZnO/Ag interface, instead of the cSi/ZnO interface -3. Multiperiodic pattern on thin film INL : Outline

3. 3 I: Simulation for Laser Interference Lithography sample (PI32) -One of the goal of WP1 : Determine the optimized nanopattern for solar cells -FDTD simulation: determination of the optical absorption in the PECVD Si layer  estimation of the potential Jsc PECVD Si n doped Si substrate Vertical stack under consideration See WP2 for LIL

4. 4 I: Simulation for Laser Interference Lithography sample (PI32) -Description of the stack : -FDTD simulation: determination of the optical absorption in the PECVD Si layer only PECVD Si n doped Si substrate p 2re PECVD Si n doped Si substrate H  1.5µm At the beginning:At the end : aSi (20nm) ITO (50nm) only 10nm on vertical sidewall See WP2 for LIL

5. 5 I: Simulation for Laser Interference Lithography sample (PI32) -Optimal PC parameters : p=450nm, e=150nm, r=140nm  Jsc = 13.5mA/cm² p=600nm, e=200nm, r=215nm  Jsc = 13.7mA/cm² -Experimental results: Experimental deviation from the optical target…  Update of the optical simulation based on the experimental structure PECVD Si n doped Si substrate p 2re aSi (20nm) ITO (50nm) only 10nm on vertical sidewall See WP2 for LIL

6. 6 I: Simulation for Laser Interference Lithography sample (PI32) -Experimental PC parameters : p=450nm, e=100nm, r=130nm  Jsc = 13.0mA/cm² p=450nm, e=150nm, r=175nm  Jsc = 13.4mA/cm² p=600nm, e=180nm, r=205nm  Jsc = 13.6mA/cm² nb: without back interface, no Slow Bloch modes so no oscillations in the absorption spectrum PECVD Si n doped Si substrate p 2re aSi (20nm) ITO (50nm) only 10nm on vertical sidewall See WP2 for LIL

7. Nanopatterning induces electrical defects -Wet etching seems to be better than Dry etching: we focus us on inverted pyramid design. -But lifetime is still divided by a factor 2. -Can we define an efficient light trapping design without adding electrical defects? 2. Possible alternative: patterning of the front electrode only ITO 200 nm RIE on PI32 sample SEM from LPICM

8. -Comparison between patterned active layer and patterned TCO for an EPIFREE configuration : Jsc = 14.0mA/cm² Jsc = 11.8mA/cm² Can the optical losses be compensated by electrical gain? 2. Possible alternative: patterning of the front electrode only aSi 25nm ITO 75nm cSi 1.1µm Al -15% cSi 1.1µm Al

9. NB: Approach considered in D1.6 Modelled Potential of double-side patterning 3. Double side patterning: back side patterning at ZnO/Ag interface, instead of the cSi/ZnO interface cSI 6µm BSF 100nm Ag (opt. thick) ITO ZnO aSi cSI 6µm BSF 100nm Ag (opt. thick) ITO ZnO aSi cSI 6µm BSF 100nm Ag (opt. thick) ITO ZnO aSi ITO Multilayer:Front pattern :Double-side pattern:

10. -Almost the same relative enhancement between front and dual pattern for 1D and 2D structure. 3. Double side patterning: back side patterning at ZnO/Ag interface, instead of the cSi/ZnO interface Structure Jsc (mA/cm²) Abso.Rel. multilayer27.5 1D PC front pattern31.7+15.2% 1D PC dual pattern33.1+20.4%+4.5% 2D PC front pattern33.3+22.1% 2D PC dual pattern34.5+26.3%+3.4% cSI 6µm BSF 100nm Ag (opt. thick) ITO ZnO aSi NB: all the results are given after optimization

11.  Jsc of the dual-side pattern cell correspond to the Jsc of a 23µm thick flat cell -Thickness enhancement factor is more than 3! 3. Double side patterning: back side patterning at ZnO/Ag interface, instead of the cSi/ZnO interface Si thickness of a flat cell Jsc (mA/cm²) cSI 6µm BSF 100nm Ag (opt. thick) ITO ZnO aSi

12. -Linked to the deliverable Optimal Cell Designs (D1.8) : -Can be used as supplementary information (or input) for the deliverable Experimental Non-Periodic Pattern films (D2.5) : -Preliminar step on a simple design : -Why this design? only few optical modes 4. Multiperiodic pattern on thin-film 200nm aSi:H glass

13. -Determination of the best periodic PC parameters : 4. Multiperiodic pattern on thin-film nb: max. Jsc = 24mA.cm² 200nm aSi:H glass p=345nm ff=0.50 (r=138nm) FOM=58.76% p=420nm ff=0.39 (r=148nm) FOM=56.52% p=340nm ff=0.50 (r=136nm) FOM=58.65% Square lattice of air holesHexagonal lattice« Kagome » lattice FOM=1 (full optical absorption)

14. -Particle Swarm Optimization on 2x2 supercell : -The optimization lead to a design which is almost unperturbed … 4. Multiperiodic pattern on thin-film p=345nm ff=0.50 FOM=58.76% Square lattice period (p) from 300 to 400nm Filling factor (ff) from 0 to 1 hole shift (dx) from 0 to period  3 different parameters 2 x period p=386.4nm ff=0.7165 dx=0.4917 FOM=62.37% nb: max. Jsc = 24mA.cm² 200nm aSi:H glass

15. -Particle Swarm Optimization on 2x2 supercell : -The optimization lead to a design which is almost unperturbed … but the FOM is clearly dependant on distance between holes 4. Multiperiodic pattern on thin-film period (p) from 300 to 400nm Filling factor (ff) from 0 to 1 hole shift (dx) from 0 to period  3 different parameters 2 x period p=386.4nm ff=0.7165 dx=0.4917 FOM=62.37% nb: max. Jsc = 24mA.cm² 200nm aSi:H glass

16. -Particle Swarm Optimization on 2x2 supercell : -The optimization lead to a design which is almost unperturbed … but the FOM is clearly dependant on distance between holes and the FOM is non-robust in regard to the filling factor 4. Multiperiodic pattern on thin-film period (p) from 300 to 400nm Filling factor (ff) from 0 to 1 hole shift (dx) from 0 to period  3 different parameters 2 x period p=386.4nm ff=0.7165 dx=0.4917 FOM=62.37% nb: max. Jsc = 24mA.cm² 200nm aSi:H glass

17. -Particle Swarm Optimization on 3x3 supercell : 4. Multiperiodic pattern on thin-film p=345nm ff=0.50 FOM=58.76% Square lattice period from 325 to 375nm ff from 0.2 to 0.8 (3 different values) hole shift from 0 to period (2 different values)  6 different parameters 3 x period nb: max. Jsc = 24mA.cm² 200nm aSi:H glass

18. -Particle Swarm Optimization on 3x3 supercell : -For this thin film configuration, the optimized design exhibit an absorption which is 2% higher than the unperturbed design. 4. Multiperiodic pattern on thin-film Square lattice FOM=60.29% p=345nm ff=0.50 FOM=58.76% nb: max. Jsc = 24mA.cm² 200nm aSi:H glass

19. Conclusion and perspectives -1. Simulation for Laser Interference Lithography sample (PI32): -see experimental nanopatterns in WP2 presentation -see electrical results in WP3? -2. Active layer without pattern: -lower optical absorption but without adding electrical defects -3. Multiperiodic nanopattern on thin-film: -can increase the optical absorption -thicker realistic multilayer system (with back metal, TCO, …) need to be considered

20. nanophotonics for ultra-thin crystalline silicon photovoltaics project 309127