By Ching-Hsi Lin, ITRI/Green Energy & Environment Research Labs; Chien-Hua Lung, ITRI/Green Energy & Environment Research Labs; Yang-Fang Chen, Technical Adviser, Neo Solar Power Corporation; Yu-Wei Ta, Deputy Manager, Neo Solar Power Corporation, National Taiwan University/Department of Physics; Wei-Chih Hsu, ITRI/Green Energy & Environment Research Labs
A selective emitter is a doping layer that is heavily doped beneath the electrode and lightly doped in between the electrode grids. One of the disadvantages of conventional selective-emitter techniques is the need for a high phosphorus surface concentration to obtain low contact resistance and limit the shunts in the emitter. Effective emitter passivation below the contact is difficult because of the use of emitters with low sheet resistances and high doping concentrations. In this study, the selective emitter in the optimized light/light sheet-resistance combination was formed to reduce recombination under the metal contact. The fabrication of optimized light/light doped emitters was performed using a single-step diffusion process. Besides the benefit of low surface recombination for light/light combination, this approach also removes the need for a very precise alignment between the opened emitter pattern and the front screen-printed silver fingers. This work illustrates the achievement of an efficiency improvement of more than 0.4% absolute in large-scale production for selective emitter solar cells.