Hbaromega Applies LBIC Characterization In BC Solar Cell Analysis

Back-contact (BC) solar cells are emerging as an important technology pathway as manufacturers explore higher-efficiency architectures beyond established solutions such as TOPCon. While TOPCon remains the industry’s workhorse technology, several manufacturers are actively evaluating BC designs, with some already scaling production to multi-gigawatt levels. However, these architectures require further optimization due to their more complex device behavior. These characteristics make accurate characterization critical for optimizing BC device performance.

In BC solar cells, charge carriers must travel vertically through the bulk material and then laterally toward interdigitated rear contacts. The spacing between these contacts typically ranges from about 0.5 to 2 mm, requiring carriers to diffuse laterally over distances of roughly 250 to 1,000 µm before collection. As a result, effective diffusion length requirements often exceed 1 mm, shifting device performance toward transport limitations rather than recombination.

Addressing these challenges, India-based technology company Hbaromega (ℏω) Private Limited has applied its Light Beam Induced Current (LBIC) technology to the analysis of BC solar cells, reporting encouraging initial results. LBIC operates by scanning a focused laser beam across the solar cell surface while recording the generated photocurrent, producing a high-resolution map of carrier collection efficiency. This enables the identification of performance-limiting defects such as microcracks, recombination-active regions, and transport non-uniformities.

Unlike luminescence-based techniques such as electroluminescence (EL) and photoluminescence (PL), which rely on emitted light signals, LBIC directly measures collected current under short-circuit conditions. This provides a more direct indicator of carrier transport behavior within photovoltaic devices.

Explaining this behavior, Prashant Kumar, CTO of Hbaromega, noted that the relatively large spacing between rear contacts increases lateral transport distances and diffusion length requirements, making device performance more transport-limited than recombination-limited.

This capability is particularly relevant for BC architectures, where both vertical and lateral carrier transport influence device performance. The technique can identify rear-contact recombination, recombination between p+ and n+ regions, bulk lifetime non-uniformities, and lateral transport bottlenecks. Correlating spatial LBIC responses with contact geometry and probe wavelength also enables the analysis of contact misalignment effects and process-induced degradation zones.

Conventional characterization techniques such as EL and PL may not fully capture transport-related limitations due to internal light scattering, which reduces spatial resolution. According to Prof. K. S. Narayan, Founder Director of Hbaromega, the key advantage of LBIC lies in the precision of its probing mechanism. “In EL and PL, the semiconductor itself acts as the light source, and the emitted light scatters within the device, reducing spatial resolution. LBIC, in contrast, employs an external, highly focused light spot that directly probes the sample. This eliminates internal scattering and significantly improves measurement precision.”

Another key development highlighted by the company is the improvement in measurement speed. Historically, LBIC has been limited by scanning speed, with full-area mapping of a standard M10 solar cell taking several hours depending on spatial resolution. Hbaromega reports that advances in high-speed beam positioning, fast data acquisition, optimized scanning algorithms, and parallel signal processing now enable full-area mapping within seconds. This significantly improves throughput and supports potential deployment in industrial environments.

The company offers 2 characterization platforms for solar cell and module diagnostics: PV Vision Pro for solar cells and ModuleXpert for modules. Both systems integrate LBIC alongside EL and PL, providing a multi-modal diagnostic approach for photovoltaic manufacturing and research applications.

Hbaromega (ℏω) Private Limited was founded in 2019 at the Jawaharlal Nehru Centre for Advanced Scientific Research in Bengaluru. The company focuses on developing advanced photovoltaic characterization technologies for research institutions and the solar manufacturing industry. Through locally engineered instrumentation and physics-driven diagnostics, Hbaromega aims to support the evolving requirements of next-generation photovoltaic manufacturing.