Turning Thin Film Photovoltaic Breakthroughs into Scalable Processes with Close Space Sublimation Deposition Control

NTI Nanofilm’s Close Space Sublimation (CSS) platform helps developers turn promising absorber materials into repeatable, scalable thin film processes.

Thin-film photovoltaics are moving from material exploration to process validation.

For developers working on CdTe, perovskites, chalcogenides, and other thin-film absorber systems, the challenge is no longer limited to achieving high efficiency in small-area cells. The harder task is to reproduce the same film quality across larger substrates, multiple batches and more demanding process conditions.

As substrate area increases, deposition control becomes critical. Film thickness, composition stability, thermal uniformity and batch-to-batch repeatability can directly affect device performance and scale-up confidence.

This is where deposition equipment becomes more than a laboratory tool. It becomes the process foundation that determines whether a thin film material system can move from research validation toward pilot line development.

NTI Nanofilm’s CSS platform is designed to support this transition by helping customers build controlled deposition windows, generate repeatable process data and prepare for future scale-up requirements.

When the Photovoltaic market expands, process readiness becomes the next commercial gate

China’s solar market continues to grow at scale, with solar power installed capacity reaching approximately 890 million kilowatts by the end of 2024, representing 45.2% year on year growth. This creates opportunities for thin film PV technologies, especially in lightweight formats, building integrated photovoltaics, flexible substrates and non-standard installation surfaces.

At the policy level, China’s energy transition continues to support advanced photovoltaic technology and equipment development through the 14th Five Year Plan for Energy Technology Innovation. The 2024 to 2025 Action Plan for Energy Conservation and Carbon Reduction also reinforces the wider push for non-fossil energy consumption and photovoltaic deployment.

However, market demand does not remove the engineering challenge.

For thin film PV to move closer to industrial adoption, developers must prove that their process can deliver consistent film quality beyond small-area demonstrations. Peak efficiency remains important, but it is no longer enough on its own.

The next commercial gate is process readiness. Larger area devices require film uniformity across wider substrates. Pilot line validation requires transferable process windows, repeatable batches and stable equipment control.

This is why deposition control sits at the centre of thin film PV scale-up.

When the cell area increases, deposition uniformity becomes the real bottleneck

Thin film PV is highly sensitive to process conditions.

As the device area increases, small process variations become more visible and harder to manage. Non-uniform deposition can affect film thickness, grain growth, composition, interface quality and final device performance.

This is one reason why laboratory results often become harder to reproduce in a larger area.

The industry benchmark is shifting from single cell peak efficiency toward large area uniformity, batch to batch repeatability and precise process control. The wider thin film PV market is also moving toward stronger industrialisation interest, supported by ongoing activity in CdTe, CIGS and perovskite-related technologies. (Qianzhan)

The root issue is not only material chemistry. It is also the capability ceiling of the deposition platform.

If the platform cannot control temperature, spacing, vapour transport, deposition rate and process atmosphere with enough precision, the process window remains narrow and difficult to scale.

Close Space Sublimation matters because short source to substrate spacing improves control over film formation

Close Space Sublimation (CSS) is a vapour phase deposition method where the source material and substrate are positioned close together.

During the process, the source material is heated until it sublimates. The vapour then travels across a short gap and condenses onto the substrate to form a thin film.

For thin film PV development, this short source to substrate distance can support faster deposition, higher material transfer efficiency and stronger control over film growth conditions.

CSS is already a recognised process route in CdTe thin film solar manufacturing. It is also relevant for developers working with CdTe, perovskites and other advanced absorber layers, as it helps connect material formulation with controllable film formation.

Key CSS control points include source temperature, substrate temperature, source to substrate spacing, process atmosphere, deposition time and source configuration.

For technical teams, CSS does not only deposit a film. It helps define the process window behind the film.

NTI Nanofilm Close Space Sublimation is positioned as a process development platform, not just deposition equipment

NTI Nanofilm’s CSS platform is designed to support the process development stage between laboratory research and future pilot line scale-up.

Many thin-film PV teams do not only need another laboratory system. They need a platform that helps them generate repeatable process data, optimise deposition conditions and assess scale-up feasibility earlier.

Backed by 25 years of thin film coating engineering experience, NTI Nanofilm is developing CSS as a dedicated platform for next-generation thin film photovoltaics.

Core platform capabilities include:

Parameter	NTI Nanofilm CSS platform specification
Maximum source temperature	700°C
Maximum substrate temperature	600°C
Film thickness uniformity	±2%
Film thickness range	2 to 5 μm
Thickness precision	0.1 μm
Source to substrate spacing	2 to 10 mm, precisely adjustable
Process atmosphere	Ar, O₂, N₂ multi channel independent control
System design	Modular and configurable across different R&D stages

These capabilities address key scale-up challenges. The adjustable source to substrate gap supports controlled vapour transport and deposition rate tuning. The ±2% film thickness uniformity target helps address large area consistency. Independent Ar, O₂ and N₂ gas control gives teams more flexibility to study material behaviour under different atmosphere conditions.

Together, these features help customers move from isolated trial results toward structured and repeatable process development.

The platform supports multiple absorber systems, giving customers a broader thin film development pathway

Thin film PV is not limited to one material family.

Customers may be working on CdTe, perovskites, chalcogenides, buffer layers, transparent electrodes or tandem structures. A useful CSS platform, therefore, needs to support more than one research pathway.

NTI Nanofilm’s CSS platform can support material systems such as CdTe and CdS, CsPbI₃ and FAPbI₃, Sb₂S₃ and Sb₂Se₃, and ZnO.

For universities and research institutes, it supports structured material and process studies. For industrial developers, it helps generate process data that can inform pilot line planning. For ecosystem partners, it provides a stronger foundation for discussing manufacturability, not just laboratory performance.

From “can it work?” to “can it scale?”

The commercialisation challenge for thin film PV is not simply about achieving a promising result once. It is about making the process reliable enough to move forward.

That requires deposition control, thermal control, repeatable film formation and process data that can be used beyond one laboratory experiment.

NTI Nanofilm’s CSS platform is being developed to support this transition. Laboratory systems are currently being commissioned, with active collaborations underway with universities to advance thin-film PV process development.

The platform roadmap also includes multi-source co-deposition, in situ process monitoring, controlled atmosphere optimisation and roll-to-roll compatibility for flexible substrates.

For customers working on thin film PV, the value of CSS is clear. It helps turn promising absorber materials into controlled, repeatable and scalable deposition processes.

For NTI Nanofilm, the role of the CSS platform is not only to support film deposition but to help customers build the process confidence needed to move from laboratory results toward pilot line readiness.

If you are developing thin film photovoltaic processes and would like to explore how NTI Nanofilm’s CSS platform can support your material system, process studies or scale-up roadmap, scan the QR code below to connect with us.