Selective emitter using a screen printed etch barrier in crystalline silicon solar cell

Area of Science:

• Materials Science
• Photovoltaics
• Semiconductor Device Physics

Background:

• Selective emitters are crucial for improving solar cell efficiency.
• Traditional methods for selective emitter fabrication can be costly and complex.
• Optimizing doping profiles is key to enhancing solar cell performance, particularly blue light response.

Purpose of the Study:

• To develop a low-cost and efficient wet etching process for selective emitter fabrication.
• To investigate the control of contact resistance in selective emitters using wet etching.
• To demonstrate the performance improvement of solar cells fabricated with the optimized wet etch-back process.

Main Methods:

• Optimization of wet etching conditions (curing time, etchant concentration, etching time) using an acid barrier paste.
• Screen printing of acid barrier paste followed by wet etching with HF and HNO3 solution.
• Fabrication and characterization of 12.5x12.5 cm2 solar cells with wet etch-back selective emitters.

Main Results:

• Achieved high sheet contact resistance of 90 Ω/sq with optimized wet etching.
• Doping concentrations ranged from 2x10^21 cm-3 to 7x10^19 cm-3.
• Fabricated solar cells demonstrated a short-circuit current density (Jsc) of 37 mAcm-2, open-circuit voltage (Voc) of 638.3 mV, and efficiency of 18.13%.

Conclusions:

• The developed wet etch-back process is a controllable, fast, and low-cost method for selective emitter fabrication.
• This method significantly improves solar cell performance, achieving a 13 mV higher Voc compared to reactive-ion etching.
• The optimized process offers a viable alternative for enhancing the efficiency of silicon solar cells.