Potential of interdigitated back-contact silicon heterojunction solar cells for liquid phase crystallized silicon on glass with efficiency above 14%

Abstract

Liquid phase crystallization of silicon (LPC-Si) on glass is a promising method to produce high quality multi-crystalline Si films with macroscopic grains. In this study, we report on recent improvements of our interdigitated back-contact silicon heterojunction contact system (IBC-SHJ), which enabled open circuit voltages as high as 661 mV and efficiencies up to 14.2% using a 13 µm thin n-type LPC-Si absorbers on glass. The influence of the BSF width on the cell performance is investigated both experimentally and numerically. We combine 1D optical simulations using GenPro4 and 2D electrical simulations using Sentaurus™ TCAD to determine the optical and electrical loss mechanisms in order to estimate the potential of our current LPC-Si absorbers. The simulations reveal an effective minority carrier diffusion length of 26 µm and further demonstrate that a doping concentration of 4×10 16 cm-3 and a back surface field width of 60 µm are optimum values to further increase cell efficiencies.

Passivation of Liquid‐Phase Crystallized Silicon With PECVD‐SiNx and PECVD‐SiNx/SiOx

“…As reported previously, the passivation quality at the front‐side of LPC‐Si absorbers does not limit the performance of current LPC‐Si solar cells when S eff,front is below 200 cm s −1 . Correspondingly, LPC‐Si solar cells based on the O/N and O/N/O IL stack have within error margins the same performance (Figure S1, Supporting Information).…”

“…The employment of other characterization techniques, such as capacitance‐voltage ( C – V ) measurements, is not straight forward since the glass substrate blocks one side of the interface of interest. The surface recombination velocity ( S eff,front ) at the buried front‐side IL/LPC‐Si interface is commonly determined indirectly by fitting measured solar cell parameters using simulation tools such as AFORS‐HET, ASPIN3, and TCAD Sentaurus™ . Corresponding results obtained for various IL stacks adjacent to LPC‐Si are listed in Table .…”

Toward High Solar Cell Efficiency with Low Material Usage: 15% Efficiency with 14 μm Polycrystalline Silicon on Glass

“…LPC‐Si films have grain sizes on the centimeter scale in the scanning direction and millimeter scale in the perpendicular direction. V OC values of up to 661 mV in 0.6 cm 2 cells have been reported, which are comparable with the 674 mV constituting the current record efficiency shown on multicrystalline silicon wafers . This work showcases a new in‐house record efficiency of 15.1% and potential for ≥16% in the near future with an optimization of series resistance.…”

“…However, in the thickness regime of 10–20 μm silicon, only 16.8% efficiency has been demonstrated with epitaxially grown 20 μm silicon . Liquid‐phase‐crystallized silicon (LPC‐Si) is the other successful approach in this thickness range, previously demonstrating up to 14.2% efficiency despite illumination through glass . Amorphous/nanocrystalline silicon is first deposited on a foreign substrate (e.g., glass), and locally melted into liquid state and crystallized with a moving, line‐shaped energy source .…”

Multicrystalline Silicon Thin‐Film Solar Cells Based on Vanadium Oxide Heterojunction and Laser‐Doped Contacts

“…If this condition was fulfilled, photogenerated carriers out of the emitter regions could be collected. Lifetime values in the range of a few microseconds are reported in the literature, leading to diffusion lengths of ≈50 μm. Consequently, a combination of both strategies could be a feasible solution to fully exploit the potential of laser‐doped contacts on LPC thin films.…”