3D simulations of interdigitated back-contacted crystalline silicon solar cells on thin substrates

• Published in: Solar energy Vol. 167; pp. 242 - 250
• Main Authors: Jin, Chen, Martín, Isidro, Ortega, Pablo R., Calle, Eric, Alcubilla, Ramon
• Format: Journal Article Publication
• Language: English
• Published: New York Elsevier Ltd 01-06-2018; Pergamon Press Inc
• Subjects: 3D TCAD; Circuits; Computer simulation; Crystal structure; Crystallinity; Current density; Cèl·lules solars; Dark current; Diffusion length; Doping; Electrical shading; Emitters; Energia solar fotovoltaica; Energies; High temperature; Interdigitated back contact (IBC); Open circuit voltage; Photovoltaic cells; Recombination; Reduction; Short circuit currents; Short-circuit current; Silicon; Silicon substrates; Solar cells; Solar energy; Substrates; Surface treatment; Thin c-Si substrate; Àrees temàtiques de la UPC; Interdigitated back contact (IBC); 3D TCAD; Electrical shading; Thin c-Si substrate
• ISSN: 0038-092X; 1471-1257
• DOI: 10.1016/j.solener.2018.04.022

•An efficiency potential of 16–17% for 10–15 µm c-Si IBC solar cell is reachable.•Front surface passivation requirements are relaxed for thinner cells.•Locally-doped cell is less tolerant to the degradation of the surface passivation.•The Leff of locally-doped cellis highly impacted by the electrical shading effect.•Voc is not negatively impacted by thinning substrates due to a reduction of J0.
Interdigitated back contact technology is a promising candidate to be applied to thin crystalline silicon solar cells because of its simpler one-side interconnection while allowing a more flexible front surface treatment. This work explores the efficiency potential of IBC c-Si solar cells applied to thin c-Si substrates through 3D device simulations. In particular, we explore the impact of substrate thickness and front surface recombination velocity on cell performance with special attention to the different behavior in carrier collection of two different rear-surface doping structures. Firstly, the model is validated by comparing simulation results to a fabricated device on 280 µm-thick substrates with stripe-like p+ and n+ diffusions. It is revealed that efficiencies of 16–17% are reachable for substrates on the 10–15 µm range without changing the technology developed for thick ones. Next, the rear doping structure is modified leading to doped regions just under the metal contacts. This type of structure is expected in solar cells where high-temperature diffusions are replaced by point-like laser doped contacts, which is a feasible alternative to be applied to thin substrates. Simulation results show that diffusion length requirements for those locally-doped structures are more demanding due to the reduction of emitter regions. As a result, very well passivated front and rear surfaces are required to maintain short-circuit current densities to reasonable values. Finally, for both structures open-circuit voltage is kept almost constant with reduced thickness, despite the strong reduction in short-circuit current. Simulations show a reduction of dark saturation current density with substrate thinning due to the redistribution of dark current densities that flow parallel to the device surface.