LabAdviser/Technology Research/Technology for CZTS-Silicon Tandem Solar Cells - Revision history

Mmat: /* Fabrication: Process flows */

2025-05-27T16:09:50Z

Fabrication: Process flows

← Older revision		Revision as of 18:09, 27 May 2025
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	'''[4]''' Gansukh, M., López Mariño, S., Espindola Rodriguez, M., Engberg, S. L. J., Martinho, F. M. A., '''Hajijafarassar, A.''', Schjødt, N. C., Stamate, E., Hansen, O., Schou, J., & Canulescu, S. (2020). Oxide route for production of Cu2ZnSnS4 solar cells by pulsed laser deposition. Solar Energy Materials and Solar Cells, 215, 110605. https://doi.org/10.1016/j.solmat.2020.110605		'''[4]''' Gansukh, M., López Mariño, S., Espindola Rodriguez, M., Engberg, S. L. J., Martinho, F. M. A., '''Hajijafarassar, A.''', Schjødt, N. C., Stamate, E., Hansen, O., Schou, J., & Canulescu, S. (2020). Oxide route for production of Cu2ZnSnS4 solar cells by pulsed laser deposition. Solar Energy Materials and Solar Cells, 215, 110605. https://doi.org/10.1016/j.solmat.2020.110605

	~~==Fabrication: Process flows ==~~

	The fabrication process flow of the silicon bottom cell can be found via the link below. Note that the process flow only contains fabrication steps of the device precursor wafer (asymmetrically passivated wafer with selective polySi-based contacts), and not include the backend processing (TCO deposition, metallization, tandem integration, etc.).

	~~Process flow (word format):~~
	*[[media:Doubled-side TOPCon structure for Si-based tandems.docx\|Silicon Bottom Cell Device Precursor - Process flow]]

Alhaj: /* Project description */

2020-12-04T13:13:48Z

Project description

← Older revision		Revision as of 15:13, 4 December 2020
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	Thanks to the drastic cost reductions over the last few decades, photovoltaic (PV) technology, which directly converts the sunlight into usable electricity, has become one of the most prominent sources of renewable energy. As the balance of system costs now dominates the cost of PV systems, the demand to increase the efficiency of PV modules has surged. However, the efficiency improvements in most mature PV technologies, in particular the Si solar cells as the most dominant technology, are only marginal as they are approaching their fundamental limits. In this regard, multijunction or tandem solar cells have emerged as the most compelling solution to surpass the so-called Shockley–Queisser limit and realize efficiency beyond 30%. In a tandem solar cell, two (or more) sub-cells with complementary bandgaps are combined in a vertical stack to harvest the solar spectrum more efficiently with lower thermalization (heat) losses. Silicon-based tandem solar cells, which couple the conventional silicon technology with a high bandgap material, are practically and economically the most favorable configuration since the enhanced efficiency can be realized by adding a few additional steps to the existing well-developed technology. Thin-film chalcogenides are enticing candidates for the top cell material as they have exhibited cost, performance, and stability comparable to the silicon technology. Despite their promise, the growth of such materials, which are usually produced at high temperatures (500-600 oC) under harsh reactive atmospheres (e.g., S or Se), on silicon is exceptionally challenging. During the high-temperature process, harmful metallic elements (e.g., Cu), which chalcogenides contain in abundance, can diffuse to the silicon bottom cell and severely damage its photovoltaic performance.		Thanks to the drastic cost reductions over the last few decades, photovoltaic (PV) technology, which directly converts the sunlight into usable electricity, has become one of the most prominent sources of renewable energy. As the balance of system costs now dominates the cost of PV systems, the demand to increase the efficiency of PV modules has surged. However, the efficiency improvements in most mature PV technologies, in particular the Si solar cells as the most dominant technology, are only marginal as they are approaching their fundamental limits. In this regard, multijunction or tandem solar cells have emerged as the most compelling solution to surpass the so-called Shockley–Queisser limit and realize efficiency beyond 30%. In a tandem solar cell, two (or more) sub-cells with complementary bandgaps are combined in a vertical stack to harvest the solar spectrum more efficiently with lower thermalization (heat) losses. Silicon-based tandem solar cells, which couple the conventional silicon technology with a high bandgap material, are practically and economically the most favorable configuration since the enhanced efficiency can be realized by adding a few additional steps to the existing well-developed technology. Thin-film chalcogenides are enticing candidates for the top cell material as they have exhibited cost, performance, and stability comparable to the silicon technology. Despite their promise, the growth of such materials, which are usually produced at high temperatures (500-600 oC) under harsh reactive atmospheres (e.g., S or Se), on silicon is exceptionally challenging. During the high-temperature process, harmful metallic elements (e.g., Cu), which chalcogenides contain in abundance, can diffuse to the silicon bottom cell and severely damage its photovoltaic performance.

	In this thesis, we chose ~~Cu_2ZnSnS_4~~, a quaternary compound semiconductor with a bandgap of 1.5 eV, as a promising non-toxic, earth-abundant, and cheap representative candidate from the chalcogenide family, and systematically studied the integration challenges with silicon. For this purpose, we developed and optimized a thermally resilient silicon cell structure with polysilicon carrier selective contacts, and used an ultrathin (< 10 nm) titanium nitride-based diffusion barrier at the interface of the two cells (called the “barrier layer”) to protect the silicon cell against contamination. Throughout the thesis, we showed that the performance of the CZTS-Si tandem devices heavily relies on the electrical, optical, and protection behavior of the barrier layer. By proper engineering of the TiN and polysilicon interfacial layers, we managed to keep the silicon cell almost intact during the full fabrication of CZTS, and demonstrated a world-record efficiency of 4.1% for this type of structure. Our findings implicate that the growth of new materials, with a wide range of thermal budgets and compositions, is technically feasible on silicon. Moreover, we believe that our proposed tandem structure may provide new insights for the Si community in terms of device architecture engineering for future silicon-based tandem cells.		In this thesis, we chose Cu2ZnSnS4, a quaternary compound semiconductor with a bandgap of 1.5 eV, as a promising non-toxic, earth-abundant, and cheap representative candidate from the chalcogenide family, and systematically studied the integration challenges with silicon. For this purpose, we developed and optimized a thermally resilient silicon cell structure with polysilicon carrier selective contacts, and used an ultrathin (< 10 nm) titanium nitride-based diffusion barrier at the interface of the two cells (called the “barrier layer”) to protect the silicon cell against contamination. Throughout the thesis, we showed that the performance of the CZTS-Si tandem devices heavily relies on the electrical, optical, and protection behavior of the barrier layer. By proper engineering of the TiN and polysilicon interfacial layers, we managed to keep the silicon cell almost intact during the full fabrication of CZTS, and demonstrated a world-record efficiency of 4.1% for this type of structure. Our findings implicate that the growth of new materials, with a wide range of thermal budgets and compositions, is technically feasible on silicon. Moreover, we believe that our proposed tandem structure may provide new insights for the Si community in terms of device architecture engineering for future silicon-based tandem cells.

	==Publications in peer-reviewed journal papers==		==Publications in peer-reviewed journal papers==

Alhaj: /* Project description */

2020-12-04T13:13:40Z

Project description

← Older revision		Revision as of 15:13, 4 December 2020
Line 13:		Line 13:
	Thanks to the drastic cost reductions over the last few decades, photovoltaic (PV) technology, which directly converts the sunlight into usable electricity, has become one of the most prominent sources of renewable energy. As the balance of system costs now dominates the cost of PV systems, the demand to increase the efficiency of PV modules has surged. However, the efficiency improvements in most mature PV technologies, in particular the Si solar cells as the most dominant technology, are only marginal as they are approaching their fundamental limits. In this regard, multijunction or tandem solar cells have emerged as the most compelling solution to surpass the so-called Shockley–Queisser limit and realize efficiency beyond 30%. In a tandem solar cell, two (or more) sub-cells with complementary bandgaps are combined in a vertical stack to harvest the solar spectrum more efficiently with lower thermalization (heat) losses. Silicon-based tandem solar cells, which couple the conventional silicon technology with a high bandgap material, are practically and economically the most favorable configuration since the enhanced efficiency can be realized by adding a few additional steps to the existing well-developed technology. Thin-film chalcogenides are enticing candidates for the top cell material as they have exhibited cost, performance, and stability comparable to the silicon technology. Despite their promise, the growth of such materials, which are usually produced at high temperatures (500-600 oC) under harsh reactive atmospheres (e.g., S or Se), on silicon is exceptionally challenging. During the high-temperature process, harmful metallic elements (e.g., Cu), which chalcogenides contain in abundance, can diffuse to the silicon bottom cell and severely damage its photovoltaic performance.		Thanks to the drastic cost reductions over the last few decades, photovoltaic (PV) technology, which directly converts the sunlight into usable electricity, has become one of the most prominent sources of renewable energy. As the balance of system costs now dominates the cost of PV systems, the demand to increase the efficiency of PV modules has surged. However, the efficiency improvements in most mature PV technologies, in particular the Si solar cells as the most dominant technology, are only marginal as they are approaching their fundamental limits. In this regard, multijunction or tandem solar cells have emerged as the most compelling solution to surpass the so-called Shockley–Queisser limit and realize efficiency beyond 30%. In a tandem solar cell, two (or more) sub-cells with complementary bandgaps are combined in a vertical stack to harvest the solar spectrum more efficiently with lower thermalization (heat) losses. Silicon-based tandem solar cells, which couple the conventional silicon technology with a high bandgap material, are practically and economically the most favorable configuration since the enhanced efficiency can be realized by adding a few additional steps to the existing well-developed technology. Thin-film chalcogenides are enticing candidates for the top cell material as they have exhibited cost, performance, and stability comparable to the silicon technology. Despite their promise, the growth of such materials, which are usually produced at high temperatures (500-600 oC) under harsh reactive atmospheres (e.g., S or Se), on silicon is exceptionally challenging. During the high-temperature process, harmful metallic elements (e.g., Cu), which chalcogenides contain in abundance, can diffuse to the silicon bottom cell and severely damage its photovoltaic performance.

	In this thesis, we chose ~~Cu2ZnSnS4~~, a quaternary compound semiconductor with a bandgap of 1.5 eV, as a promising non-toxic, earth-abundant, and cheap representative candidate from the chalcogenide family, and systematically studied the integration challenges with silicon. For this purpose, we developed and optimized a thermally resilient silicon cell structure with polysilicon carrier selective contacts, and used an ultrathin (< 10 nm) titanium nitride-based diffusion barrier at the interface of the two cells (called the “barrier layer”) to protect the silicon cell against contamination. Throughout the thesis, we showed that the performance of the CZTS-Si tandem devices heavily relies on the electrical, optical, and protection behavior of the barrier layer. By proper engineering of the TiN and polysilicon interfacial layers, we managed to keep the silicon cell almost intact during the full fabrication of CZTS, and demonstrated a world-record efficiency of 4.1% for this type of structure. Our findings implicate that the growth of new materials, with a wide range of thermal budgets and compositions, is technically feasible on silicon. Moreover, we believe that our proposed tandem structure may provide new insights for the Si community in terms of device architecture engineering for future silicon-based tandem cells.		In this thesis, we chose Cu_2ZnSnS_4, a quaternary compound semiconductor with a bandgap of 1.5 eV, as a promising non-toxic, earth-abundant, and cheap representative candidate from the chalcogenide family, and systematically studied the integration challenges with silicon. For this purpose, we developed and optimized a thermally resilient silicon cell structure with polysilicon carrier selective contacts, and used an ultrathin (< 10 nm) titanium nitride-based diffusion barrier at the interface of the two cells (called the “barrier layer”) to protect the silicon cell against contamination. Throughout the thesis, we showed that the performance of the CZTS-Si tandem devices heavily relies on the electrical, optical, and protection behavior of the barrier layer. By proper engineering of the TiN and polysilicon interfacial layers, we managed to keep the silicon cell almost intact during the full fabrication of CZTS, and demonstrated a world-record efficiency of 4.1% for this type of structure. Our findings implicate that the growth of new materials, with a wide range of thermal budgets and compositions, is technically feasible on silicon. Moreover, we believe that our proposed tandem structure may provide new insights for the Si community in terms of device architecture engineering for future silicon-based tandem cells.

	==Publications in peer-reviewed journal papers==		==Publications in peer-reviewed journal papers==

Alhaj: /* Project description */

2020-12-04T13:13:26Z

Project description

← Older revision		Revision as of 15:13, 4 December 2020
Line 13:		Line 13:
	Thanks to the drastic cost reductions over the last few decades, photovoltaic (PV) technology, which directly converts the sunlight into usable electricity, has become one of the most prominent sources of renewable energy. As the balance of system costs now dominates the cost of PV systems, the demand to increase the efficiency of PV modules has surged. However, the efficiency improvements in most mature PV technologies, in particular the Si solar cells as the most dominant technology, are only marginal as they are approaching their fundamental limits. In this regard, multijunction or tandem solar cells have emerged as the most compelling solution to surpass the so-called Shockley–Queisser limit and realize efficiency beyond 30%. In a tandem solar cell, two (or more) sub-cells with complementary bandgaps are combined in a vertical stack to harvest the solar spectrum more efficiently with lower thermalization (heat) losses. Silicon-based tandem solar cells, which couple the conventional silicon technology with a high bandgap material, are practically and economically the most favorable configuration since the enhanced efficiency can be realized by adding a few additional steps to the existing well-developed technology. Thin-film chalcogenides are enticing candidates for the top cell material as they have exhibited cost, performance, and stability comparable to the silicon technology. Despite their promise, the growth of such materials, which are usually produced at high temperatures (500-600 oC) under harsh reactive atmospheres (e.g., S or Se), on silicon is exceptionally challenging. During the high-temperature process, harmful metallic elements (e.g., Cu), which chalcogenides contain in abundance, can diffuse to the silicon bottom cell and severely damage its photovoltaic performance.		Thanks to the drastic cost reductions over the last few decades, photovoltaic (PV) technology, which directly converts the sunlight into usable electricity, has become one of the most prominent sources of renewable energy. As the balance of system costs now dominates the cost of PV systems, the demand to increase the efficiency of PV modules has surged. However, the efficiency improvements in most mature PV technologies, in particular the Si solar cells as the most dominant technology, are only marginal as they are approaching their fundamental limits. In this regard, multijunction or tandem solar cells have emerged as the most compelling solution to surpass the so-called Shockley–Queisser limit and realize efficiency beyond 30%. In a tandem solar cell, two (or more) sub-cells with complementary bandgaps are combined in a vertical stack to harvest the solar spectrum more efficiently with lower thermalization (heat) losses. Silicon-based tandem solar cells, which couple the conventional silicon technology with a high bandgap material, are practically and economically the most favorable configuration since the enhanced efficiency can be realized by adding a few additional steps to the existing well-developed technology. Thin-film chalcogenides are enticing candidates for the top cell material as they have exhibited cost, performance, and stability comparable to the silicon technology. Despite their promise, the growth of such materials, which are usually produced at high temperatures (500-600 oC) under harsh reactive atmospheres (e.g., S or Se), on silicon is exceptionally challenging. During the high-temperature process, harmful metallic elements (e.g., Cu), which chalcogenides contain in abundance, can diffuse to the silicon bottom cell and severely damage its photovoltaic performance.

	In this thesis, we chose ~~CuZnSnS4~~, a quaternary compound semiconductor with a bandgap of 1.5 eV, as a promising non-toxic, earth-abundant, and cheap representative candidate from the chalcogenide family, and systematically studied the integration challenges with silicon. For this purpose, we developed and optimized a thermally resilient silicon cell structure with polysilicon carrier selective contacts, and used an ultrathin (< 10 nm) titanium nitride-based diffusion barrier at the interface of the two cells (called the “barrier layer”) to protect the silicon cell against contamination. Throughout the thesis, we showed that the performance of the CZTS-Si tandem devices heavily relies on the electrical, optical, and protection behavior of the barrier layer. By proper engineering of the TiN and polysilicon interfacial layers, we managed to keep the silicon cell almost intact during the full fabrication of CZTS, and demonstrated a world-record efficiency of 4.1% for this type of structure. Our findings implicate that the growth of new materials, with a wide range of thermal budgets and compositions, is technically feasible on silicon. Moreover, we believe that our proposed tandem structure may provide new insights for the Si community in terms of device architecture engineering for future silicon-based tandem cells.		In this thesis, we chose Cu2ZnSnS4, a quaternary compound semiconductor with a bandgap of 1.5 eV, as a promising non-toxic, earth-abundant, and cheap representative candidate from the chalcogenide family, and systematically studied the integration challenges with silicon. For this purpose, we developed and optimized a thermally resilient silicon cell structure with polysilicon carrier selective contacts, and used an ultrathin (< 10 nm) titanium nitride-based diffusion barrier at the interface of the two cells (called the “barrier layer”) to protect the silicon cell against contamination. Throughout the thesis, we showed that the performance of the CZTS-Si tandem devices heavily relies on the electrical, optical, and protection behavior of the barrier layer. By proper engineering of the TiN and polysilicon interfacial layers, we managed to keep the silicon cell almost intact during the full fabrication of CZTS, and demonstrated a world-record efficiency of 4.1% for this type of structure. Our findings implicate that the growth of new materials, with a wide range of thermal budgets and compositions, is technically feasible on silicon. Moreover, we believe that our proposed tandem structure may provide new insights for the Si community in terms of device architecture engineering for future silicon-based tandem cells.


	==Publications in peer-reviewed journal papers==		==Publications in peer-reviewed journal papers==

Alhaj: /* Preface */

2020-12-04T13:12:55Z

Preface

← Older revision		Revision as of 15:12, 4 December 2020
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	# Providing some of the front and back end films for the CZTS cell, participation in the characterization of the CZTS films, whereas the actual synthesis of CZTS will mostly be done by other project partners.		# Providing some of the front and back end films for the CZTS cell, participation in the characterization of the CZTS films, whereas the actual synthesis of CZTS will mostly be done by other project partners.
	# Developing and characterizing the bottom silicon cell.		# Developing and characterizing the bottom silicon cell.
	# Developing technology for tunnel/barrier layers on the silicon cell. The purpose of these layers are twofold:		# Developing technology for tunnel/barrier layers on the silicon cell. The purpose of these layers are twofold: 1) At the interface electron currents from the silicon cell must be transformed into hole currents in the CZTS cell. 2) The interface must have a diffusion barrier to protect the silicon cell from in-diffusion of metals (particularly Cu) from the CZTS. This is a particularly challenging task.
	**1) At the interface electron currents from the silicon cell must be transformed into hole currents in the CZTS cell.
	**2) The interface must have a diffusion barrier to protect the silicon cell from in-diffusion of metals (particularly Cu) from the CZTS. This is a particularly challenging task.

	==Project description==		==Project description==

Alhaj: /* Preface */

2020-12-04T13:12:17Z

Preface

← Older revision		Revision as of 15:12, 4 December 2020
Line 9:		Line 9:
	# Developing and characterizing the bottom silicon cell.		# Developing and characterizing the bottom silicon cell.
	# Developing technology for tunnel/barrier layers on the silicon cell. The purpose of these layers are twofold:		# Developing technology for tunnel/barrier layers on the silicon cell. The purpose of these layers are twofold:
	*1) At the interface electron currents from the silicon cell must be transformed into hole currents in the CZTS cell.		**1) At the interface electron currents from the silicon cell must be transformed into hole currents in the CZTS cell.
	*2) The interface must have a diffusion barrier to protect the silicon cell from in-diffusion of metals (particularly Cu) from the CZTS. This is a particularly challenging task.		**2) The interface must have a diffusion barrier to protect the silicon cell from in-diffusion of metals (particularly Cu) from the CZTS. This is a particularly challenging task.

	==Project description==		==Project description==

Alhaj: /* Preface */

2020-12-04T13:11:50Z

Preface

← Older revision		Revision as of 15:11, 4 December 2020
Line 8:		Line 8:
	# Providing some of the front and back end films for the CZTS cell, participation in the characterization of the CZTS films, whereas the actual synthesis of CZTS will mostly be done by other project partners.		# Providing some of the front and back end films for the CZTS cell, participation in the characterization of the CZTS films, whereas the actual synthesis of CZTS will mostly be done by other project partners.
	# Developing and characterizing the bottom silicon cell.		# Developing and characterizing the bottom silicon cell.
	# Developing technology for tunnel/barrier layers on the silicon cell. The purpose of these layers are twofold: [[1) At the interface electron currents from the silicon cell must be transformed into hole currents in the CZTS cell.~~]] [[~~2) The interface must have a diffusion barrier to protect the silicon cell from in-diffusion of metals (particularly Cu) from the CZTS. This is a particularly challenging task.]]		# Developing technology for tunnel/barrier layers on the silicon cell. The purpose of these layers are twofold:
			*1) At the interface electron currents from the silicon cell must be transformed into hole currents in the CZTS cell.
			*2) The interface must have a diffusion barrier to protect the silicon cell from in-diffusion of metals (particularly Cu) from the CZTS. This is a particularly challenging task.

	==Project description==		==Project description==

Alhaj: /* Preface */

2020-12-04T13:10:37Z

Preface

← Older revision		Revision as of 15:10, 4 December 2020
Line 8:		Line 8:
	# Providing some of the front and back end films for the CZTS cell, participation in the characterization of the CZTS films, whereas the actual synthesis of CZTS will mostly be done by other project partners.		# Providing some of the front and back end films for the CZTS cell, participation in the characterization of the CZTS films, whereas the actual synthesis of CZTS will mostly be done by other project partners.
	# Developing and characterizing the bottom silicon cell.		# Developing and characterizing the bottom silicon cell.
	# Developing technology for tunnel/barrier layers on the silicon cell. The purpose of these layers are twofold: 1) At the interface electron currents from the silicon cell must be transformed into hole currents in the CZTS cell. 2) The interface must have a diffusion barrier to protect the silicon cell from in-diffusion of metals (particularly Cu) from the CZTS. This is a particularly challenging task.		# Developing technology for tunnel/barrier layers on the silicon cell. The purpose of these layers are twofold: [[1) At the interface electron currents from the silicon cell must be transformed into hole currents in the CZTS cell.]] [[2) The interface must have a diffusion barrier to protect the silicon cell from in-diffusion of metals (particularly Cu) from the CZTS. This is a particularly challenging task.]]

	==Project description==		==Project description==

Alhaj: /* Preface */

2020-12-04T13:09:55Z

Preface

← Older revision		Revision as of 15:09, 4 December 2020
Line 8:		Line 8:
	# Providing some of the front and back end films for the CZTS cell, participation in the characterization of the CZTS films, whereas the actual synthesis of CZTS will mostly be done by other project partners.		# Providing some of the front and back end films for the CZTS cell, participation in the characterization of the CZTS films, whereas the actual synthesis of CZTS will mostly be done by other project partners.
	# Developing and characterizing the bottom silicon cell.		# Developing and characterizing the bottom silicon cell.
	# Developing technology for tunnel/barrier layers on the silicon cell. The purpose of these layers are twofold: 1) At the interface electron currents from the silicon cell must be transformed into hole currents in the CZTS cell. 2) The interface must have a diffusion barrier to protect the silicon cell from in-diffusion of metals (particularly Cu) from the CZTS. This is a particularly challenging task.		# Developing technology for tunnel/barrier layers on the silicon cell. The purpose of these layers are twofold: 1) At the interface electron currents from the silicon cell must be transformed into hole currents in the CZTS cell. 2) The interface must have a diffusion barrier to protect the silicon cell from in-diffusion of metals (particularly Cu) from the CZTS. This is a particularly challenging task.

	==Project description==		==Project description==

Alhaj: /* Preface */

2020-12-04T13:09:19Z

Preface

← Older revision		Revision as of 15:09, 4 December 2020
Line 7:		Line 7:

	# Providing some of the front and back end films for the CZTS cell, participation in the characterization of the CZTS films, whereas the actual synthesis of CZTS will mostly be done by other project partners.		# Providing some of the front and back end films for the CZTS cell, participation in the characterization of the CZTS films, whereas the actual synthesis of CZTS will mostly be done by other project partners.

	# Developing and characterizing the bottom silicon cell.		# Developing and characterizing the bottom silicon cell.

	# Developing technology for tunnel/barrier layers on the silicon cell. The purpose of these layers are twofold: 1) At the interface electron currents from the silicon cell must be transformed into hole currents in the CZTS cell. 2) The interface must have a diffusion barrier to protect the silicon cell from in-diffusion of metals (particularly Cu) from the CZTS. This is a particularly challenging task.		# Developing technology for tunnel/barrier layers on the silicon cell. The purpose of these layers are twofold: 1) At the interface electron currents from the silicon cell must be transformed into hole currents in the CZTS cell. 2) The interface must have a diffusion barrier to protect the silicon cell from in-diffusion of metals (particularly Cu) from the CZTS. This is a particularly challenging task.