{
  "case_study_id": "case_study_03_solar_device_stack_codesign",
  "title": "Solar Absorber Discovery and CdTe Replacement Challenge",
  "slug": "solar-device-stack-codesign",
  "generated_on": "2026-04-09",
  "description": "FluxMateria ran a full solar absorber-and-contact workflow locally in about 28 seconds, then ran a stricter incumbent-replacement challenge in about 52 seconds. The workflow found a CdTe full-stack winner and surfaced CuS and CuSe as novel CdTe-replacement lanes under the defined computational objective.",
  "public_scope": "Shareable packet with absorber formulas, contact-stack winners, replacement-candidate summaries, benchmark context, and literature grounding. It focuses on engineering decisions and supporting evidence.",
  "discovery_brief": {
    "objective": "Re-rank a curated solar absorber pool by combining bulk absorber quality, front-contact fit, back-contact fit, solar-native device scoring, uncertainty, and prototype handoff.",
    "decision_layers": [
      "Bulk absorber screening",
      "Front-contact and back-contact screening",
      "Solar-native device scoring",
      "Benchmark-calibrated uncertainty",
      "Prototype handoff",
      "Incumbent-replacement scoring"
    ],
    "key_question": "Would the same material remain the winner once absorber quality, contact-stack quality, and replacement practicality were treated as one problem?",
    "curated_pool": [
      "Si",
      "GaAs",
      "InP",
      "CdTe",
      "CuInSe2",
      "Cu2O",
      "MoS2",
      "WS2"
    ]
  },
  "headline_metrics": {
    "runtime_seconds": 28.003,
    "replacement_campaign_runtime_seconds": 51.78,
    "curated_pool_size": 8,
    "bulk_winner": "InP",
    "device_winner": "CdTe",
    "device_winner_front_contact": "ZnO",
    "device_winner_back_contact": "Mo",
    "build_winner": "Si",
    "top_replacement_candidate": "CuS",
    "top_replacement_gain_pct": 20.65,
    "replacement_candidates_clearing_gate": 2,
    "holdout_family_accuracy": 1.0,
    "scenario_alignment_rate": 1.0
  },
  "benchmark_summary": {
    "reference_count": 6,
    "holdout_reference_count": 3,
    "family_accuracy": 1.0,
    "pce_proxy_mae_pct": 1.887,
    "stability_mae": 0.035,
    "cost_mae": 0.1193,
    "manufacturing_mae": 0.0667,
    "scenario_count": 4,
    "aligned_scenarios": 4,
    "scenario_alignment_rate": 1.0,
    "scenario_winners": [
      {
        "scenario": "Balanced Device Stack",
        "winner": "CdTe"
      },
      {
        "scenario": "Low-Hazard Manufacturable Choice",
        "winner": "Si"
      },
      {
        "scenario": "Efficiency Frontier",
        "winner": "CdTe"
      },
      {
        "scenario": "Active Learning Edge Case",
        "winner": "ZnSnO3"
      }
    ],
    "calibration_note": "Calibration preserved perfect family alignment and 4/4 scenario alignment while tightening the practical engineering layers. It did not improve every benchmark metric equally."
  },
  "workflow_summary": [
    "Curated absorber framing across known photovoltaic families",
    "Bulk absorber screening against a solar-specific property brief",
    "Batched front-contact and back-contact interface sweep",
    "Solar-native device scoring with prototype-handoff outputs",
    "Benchmark-calibrated uncertainty and experiment planning"
  ],
  "pipeline_summary": [
    {
      "step": 1,
      "label": "Curated absorber framing",
      "purpose": "Keep the comparison chemically legible and benchmarkable."
    },
    {
      "step": 2,
      "label": "Bulk absorber screen",
      "purpose": "Establish the absorber-only answer before contact corrections."
    },
    {
      "step": 3,
      "label": "Batch contact sweep",
      "purpose": "Evaluate realistic front and back contacts instead of assuming absorber quality is enough."
    },
    {
      "step": 4,
      "label": "Solar-native device ranking",
      "purpose": "Rank full stacks using absorber quality, interface balance, stability, cost, and manufacturability together."
    },
    {
      "step": 5,
      "label": "Calibration and uncertainty",
      "purpose": "Attach benchmark support, confidence, and next experiments to the shortlist."
    },
    {
      "step": 6,
      "label": "Prototype handoff",
      "purpose": "Separate the strongest device-stack answer from the safest immediate build package."
    }
  ],
  "timing_context": {
    "fluxmateria_local_runtime_seconds": 28.003,
    "replacement_campaign_runtime_seconds": 51.78,
    "public_claim": "FluxMateria compressed a full solar absorber-plus-contact-stack decision workflow into about 28 seconds locally, then compressed a stricter incumbent-replacement challenge into about 52 seconds locally, while leaving device fabrication and certification to the lab.",
    "winner_shift_summary": "Bulk-only ranking chose InP. Contact-aware device ranking chose CdTe. Conservative build handoff chose Si. The replacement campaign surfaced CuS and CuSe as novel lanes that cleared the defined CdTe-replacement gate."
  },
  "replacement_campaign": {
    "objective": "Identify novel absorber lanes that can beat the CdTe + ZnO + Mo baseline on a broader replacement objective.",
    "baseline": {
      "formula": "CdTe",
      "front_contact": "ZnO",
      "back_contact": "Mo",
      "architecture": "thin_film_absorber",
      "design_goal": "efficiency"
    },
    "runtime_seconds": 51.78,
    "replacement_threshold_pct": 10.0,
    "decision_terms": [
      "device readiness",
      "PCE proxy",
      "stability",
      "manufacturing readiness",
      "cost competitiveness",
      "safety and toxicity burden",
      "supply-chain resilience",
      "interface recombination burden",
      "passivation burden",
      "novelty",
      "architecture fit"
    ],
    "top_replacement_candidates": [
      {
        "formula": "CuS",
        "best_front_contact": "ZnSe",
        "best_back_contact": "Al",
        "incumbent_replacement_score": 79.0,
        "relative_replacement_gain_pct": 20.65,
        "solar_device_readiness_score": 78.4,
        "relative_readiness_gain_pct": 0.21,
        "pce_proxy_pct": 18.09,
        "beats_baseline_as_replacement": true,
        "public_interpretation": "Highest-upside replacement hypothesis in this pass; literature-adjacent copper chalcogenide chemistry, but still requires thin-film fabrication and validation."
      },
      {
        "formula": "CuSe",
        "best_front_contact": "ZnO",
        "best_back_contact": "Mo",
        "incumbent_replacement_score": 75.4,
        "relative_replacement_gain_pct": 15.09,
        "solar_device_readiness_score": 78.4,
        "relative_readiness_gain_pct": 0.31,
        "pce_proxy_pct": 18.4,
        "beats_baseline_as_replacement": true,
        "public_interpretation": "More literature-adjacent replacement lane; preserves the ZnO / Mo contact logic while improving the modeled replacement objective."
      }
    ],
    "strong_near_misses": [
      {
        "formula": "Sn2S3Se",
        "why_it_matters": "Strong tin chalcogenide frontier lane with positive replacement score but insufficient readiness versus the CdTe baseline."
      },
      {
        "formula": "Sn2SeS3",
        "why_it_matters": "Related Sn-S-Se frontier lane that stayed scientifically interesting but did not clear the stricter replacement gate."
      },
      {
        "formula": "SnSeS",
        "why_it_matters": "Literature-aligned mixed tin chalcogenide lane that remained a useful near-miss rather than a replacement winner."
      }
    ],
    "claim_boundary": "This is a computational replacement objective, not certified device performance or proof of commercial replacement."
  },
  "decision_shift": {
    "bulk_answer": {
      "winner": "InP",
      "why": "Best direct bulk fit to the absorber-only brief inside the curated pool."
    },
    "device_answer": {
      "winner": "CdTe",
      "front_contact": "ZnO",
      "back_contact": "Mo",
      "why": "Best full-stack answer once realistic front and back contacts were modeled."
    },
    "build_answer": {
      "winner": "Si",
      "why": "Best immediate build package once risk, confidence, and prototype handoff were considered."
    },
    "largest_positive_shift": {
      "formula": "CdTe",
      "bulk_rank": 4,
      "device_rank": 1,
      "front_contact": "ZnO",
      "back_contact": "Mo"
    }
  },
  "final_shortlist": [
    {
      "candidate_id": "FM-SOL-01",
      "formula": "CdTe",
      "family_label": "Cadmium telluride",
      "role": "Top full-stack candidate",
      "architecture": "superstrate_thin_film",
      "pce_proxy_pct": 21.1,
      "solar_device_readiness_score": 72.0,
      "prototype_handoff_priority_score": 72.1,
      "prototype_handoff_label": "risk_controlled_build_candidate",
      "front_contact": "ZnO",
      "front_contact_mismatch_eV": 0.024,
      "back_contact": "Mo",
      "back_contact_mismatch_eV": 0.094,
      "stability_proxy": 0.7,
      "manufacturing_readiness_proxy": 0.821,
      "cost_competitiveness_proxy": 0.6,
      "top_risks": [
        "materials_hazard",
        "supply_chain_risk",
        "materials_hazard_review"
      ],
      "recommended_next_experiments": [
        "JV and EQE measurement on the recommended contact stack",
        "Contact resistance / barrier extraction on the chosen front and back contacts",
        "Accelerated thermal and humidity stability screen"
      ],
      "why_it_ranked": "The strongest full device-stack answer once absorber quality, contact fit, and practical engineering layers were ranked together."
    },
    {
      "candidate_id": "FM-SOL-02",
      "formula": "InP",
      "family_label": "III-V semiconductor",
      "role": "Top bulk-origin candidate",
      "architecture": "epitaxial_thin_film",
      "pce_proxy_pct": 20.29,
      "solar_device_readiness_score": 71.2,
      "prototype_handoff_priority_score": 69.9,
      "prototype_handoff_label": "risk_controlled_build_candidate",
      "front_contact": "ZnO",
      "front_contact_mismatch_eV": 0.12,
      "back_contact": "Al",
      "back_contact_mismatch_eV": 0.1,
      "stability_proxy": 0.772,
      "manufacturing_readiness_proxy": 0.564,
      "cost_competitiveness_proxy": 0.42,
      "top_risks": [],
      "recommended_next_experiments": [
        "JV and EQE measurement on the recommended contact stack",
        "Contact resistance / barrier extraction on the chosen front and back contacts",
        "Accelerated thermal and humidity stability screen"
      ],
      "why_it_ranked": "The absorber-only winner remained strong, but no longer finished first once contact quality was allowed to matter."
    },
    {
      "candidate_id": "FM-SOL-03",
      "formula": "Si",
      "family_label": "Crystalline silicon",
      "role": "Top immediate build candidate",
      "architecture": "wafer_heterojunction",
      "pce_proxy_pct": 19.81,
      "solar_device_readiness_score": 68.7,
      "prototype_handoff_priority_score": 79.0,
      "prototype_handoff_label": "risk_controlled_build_candidate",
      "front_contact": "ZnO",
      "front_contact_mismatch_eV": 0.35,
      "back_contact": "NiO",
      "back_contact_mismatch_eV": 0.24,
      "stability_proxy": 0.88,
      "manufacturing_readiness_proxy": 0.95,
      "cost_competitiveness_proxy": 0.94,
      "top_risks": [
        "weak_front_contact",
        "weak_back_contact",
        "weak_contact_evidence"
      ],
      "recommended_next_experiments": [
        "JV and EQE measurement on the recommended contact stack",
        "Contact resistance / barrier extraction on the chosen front and back contacts",
        "Accelerated thermal and humidity stability screen"
      ],
      "why_it_ranked": "Best conservative build package once handoff priority, confidence, and practical risk were considered."
    },
    {
      "candidate_id": "FM-SOL-04",
      "formula": "GaAs",
      "family_label": "III-V semiconductor",
      "role": "High-efficiency comparator",
      "architecture": "epitaxial_thin_film",
      "pce_proxy_pct": 19.27,
      "solar_device_readiness_score": 64.4,
      "prototype_handoff_priority_score": 61.9,
      "prototype_handoff_label": "de_risk_then_build",
      "front_contact": "ZnO",
      "front_contact_mismatch_eV": 0.2,
      "back_contact": "NiO",
      "back_contact_mismatch_eV": 0.09,
      "stability_proxy": 0.731,
      "manufacturing_readiness_proxy": 0.551,
      "cost_competitiveness_proxy": 0.25,
      "top_risks": [
        "supply_chain_risk",
        "weak_front_contact"
      ],
      "recommended_next_experiments": [
        "JV and EQE measurement on the recommended contact stack",
        "Contact resistance / barrier extraction on the chosen front and back contacts",
        "Accelerated thermal and humidity stability screen"
      ],
      "why_it_ranked": "A serious III-V comparator that stayed credible throughout the pipeline without becoming the final device-stack winner."
    },
    {
      "candidate_id": "FM-SOL-05",
      "formula": "WS2",
      "family_label": "Transition-metal dichalcogenide",
      "role": "Exploratory thin-film comparator",
      "architecture": "emerging_2d_photovoltaic",
      "pce_proxy_pct": 18.0,
      "solar_device_readiness_score": 63.3,
      "prototype_handoff_priority_score": 65.6,
      "prototype_handoff_label": "risk_controlled_build_candidate",
      "front_contact": "ZnO",
      "front_contact_mismatch_eV": 0.516,
      "back_contact": "Au",
      "back_contact_mismatch_eV": 0.084,
      "stability_proxy": 0.69,
      "manufacturing_readiness_proxy": 0.535,
      "cost_competitiveness_proxy": 0.881,
      "top_risks": [
        "weak_front_contact",
        "weak_contact_evidence"
      ],
      "recommended_next_experiments": [
        "JV and EQE measurement on the recommended contact stack",
        "Contact resistance / barrier extraction on the chosen front and back contacts",
        "Accelerated thermal and humidity stability screen"
      ],
      "why_it_ranked": "A useful edge-of-shortlist material that showed why absorber families beyond the traditional leaders remain worth screening."
    }
  ],
  "interesting_edge_cases": [
    {
      "formula": "CuInSe2",
      "why_it_matters": "A literature-backed chalcopyrite absorber family that remains important as a calibration and refinement target even when it does not survive the strict public shortlist.",
      "benchmark_family_match": true,
      "holdout_pce_proxy_pct": 20.93,
      "selected_reference": "https://www.sciencedirect.com/science/article/abs/pii/S0169433211017880"
    },
    {
      "formula": "Cu2O",
      "why_it_matters": "A near-threshold oxide absorber that helps stress-test how the pipeline treats lower-band-gap edge cases and manufacturable oxide chemistries."
    }
  ],
  "literature_context": [
    {
      "theme": "Established photovoltaic families",
      "takeaway": "Si, CdTe, and III-V families are all represented in NREL efficiency tracking, which supports the idea that the shortlist stayed inside real photovoltaic design space.",
      "source": "https://www.nrel.gov/pv/assets/pdfs/best-research-cell-efficiencies.20210926.pdf"
    },
    {
      "theme": "CdTe contact engineering",
      "takeaway": "CdTe front-contact band alignment has been studied directly, including ZnO-based front-contact layers, so the CdTe + ZnO winner is physically serious rather than arbitrary.",
      "source": "https://www.osti.gov/servlets/purl/1534330"
    },
    {
      "theme": "Silicon contact engineering",
      "takeaway": "Modern silicon-device performance depends heavily on passivating and selective contact design, which is why a conservative Si build package is a credible engineering outcome.",
      "source": "https://www.sciencedirect.com/science/article/abs/pii/S1369702124002088"
    },
    {
      "theme": "Chalcopyrite back contacts",
      "takeaway": "CuInSe2 and related CIGS absorbers are strongly linked to Mo / MoSe2 back-contact behavior in the literature, which is why CuInSe2 remains a meaningful edge case in this workflow.",
      "source": "https://www.sciencedirect.com/science/article/abs/pii/S0169433211017880"
    },
    {
      "theme": "Copper chalcogenide replacement lanes",
      "takeaway": "CuS and CuSe are not arbitrary formulas. The literature contains CuS photovoltaic device work, CuSe photovoltaic device work, and CuSe use around CdTe absorber modification. The exact FluxMateria replacement stacks remain experimental hypotheses.",
      "source": "https://www.mdpi.com/1996-1073/13/3/688"
    },
    {
      "theme": "Earth-abundant chalcogenide absorber context",
      "takeaway": "Tin and copper chalcogenide absorber families are active research directions for lower-cost thin-film photovoltaics, matching the chemical neighborhoods that FluxMateria surfaced in the replacement and near-miss lanes.",
      "source": "https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2019.00297/full"
    }
  ],
  "selected_references": [
    {
      "title": "NREL Best Research-Cell Efficiencies",
      "url": "https://www.nrel.gov/pv/assets/pdfs/best-research-cell-efficiencies.20210926.pdf"
    },
    {
      "title": "Band alignment of front contact layers for high-efficiency CdTe solar cells",
      "url": "https://www.osti.gov/servlets/purl/1534330"
    },
    {
      "title": "Silicon heterojunction solar cells with passivating contacts: Classification and advanced fabrication strategies",
      "url": "https://www.sciencedirect.com/science/article/abs/pii/S1369702124002088"
    },
    {
      "title": "CuInSe2 thin films: preparation, structure, properties, and solar cells",
      "url": "https://www.osti.gov/biblio/5168746"
    },
    {
      "title": "Mo/Cu(In,Ga)Se2 back interface chemical and optical properties for ultrathin CIGSe solar cells",
      "url": "https://www.sciencedirect.com/science/article/abs/pii/S0169433211017880"
    },
    {
      "title": "CuS thin-film photovoltaic device context",
      "url": "https://www.mdpi.com/1996-1073/13/3/688"
    },
    {
      "title": "CdSe/CuSe flexible photovoltaic device context",
      "url": "https://pubs.rsc.org/en/content/articlelanding/2013/cp/c3cp50435b"
    },
    {
      "title": "New Earth-Abundant Thin Film Solar Cells Based on Chalcogenides",
      "url": "https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2019.00297/full"
    },
    {
      "title": "SnSe/SnS bilayer absorber context",
      "url": "https://www.sciencedirect.com/science/article/pii/S0038092X23008083"
    }
  ],
  "downloads": {
    "white_paper": "data/FluxMateria_Solar_Absorber_Contact_Stack_WhitePaper.md",
    "public_packet": "data/solar_absorber_case_study_results.json"
  },
  "disclaimer": "This is an in-silico engineering-screening study. Device fabrication, efficiency certification, durability testing, and manufacturing validation still require real-world experimental work."
}