This study proposes a promising silicon (Si) solar cell structure for reducing the potential induced degradation (PID) of crystalline Si solar cells. Phosphorous silicate glass (PSG) layers were carefully designed on an emitter layer, and the thickness of these layers (d PSG ) was controlled by adjusting the diffusion temperature and time. The results show that the power loss remarkably decreased from 31% (d PSG = 0 nm) to 11% (d PSG = 22.3 nm) and further decreased to less than 5% after a 48-h PID test when d PSG In recent years, the number of large photovoltaic (PV) systems for generating high electricity has increased. Such PV systems contain numerous high power PV modules. Therefore, the durability of a PV module is imperative.1 The potential induced degradation (PID) of crystalline silicon (Si) solar cells, first observed by Sunpower in 2005, has drawn considerable attention in recent years. [2][3][4][5][6] This is because the local electrical short-circuiting of the pn-junction in a Si solar cell occurs under high voltage stress, which leads to a substantial reduction in the power of a module.
7Several approaches can be used to prevent PID from cell to module levels. For example, leakage current can be reduced by changing the cover glass and encapsulation materials. [8][9][10] However, applying these approaches increases the cost drastically and may cause the efficiency of solar cells to deteriorate. The soda-lime cover glass and ethylene vinyl acetate (EVA) are still the most widely used and low-cost packaging materials for solar modules. Strong demand has necessitated the modification of the antireflective layers or emitter layers in PID-resistant solar cells. However, risks should be noticed that an efficiency of a solar cell and throughput may be reduced.This study proposes a promising Si solar cell structure for reducing the PID of solar cells without influencing their efficiency and throughput. Phosphorous silicate glass (PSG) layers were carefully designed on an emitter layer to determine how they affect the efficiencies of solar cells before and after PID. A current-voltage (I-V) tester was used to determine PV parameters. An ellipseometer and transmission electron microscope (TEM) were used to measure the thicknesses of the PSG layers. Secondary ion mass spectrometry (SIMS) was used to obtain concentration profiles of Si, sodium (Na), phosphorus (P), oxygen, and nitrogen. Figure 1 shows the process flow in this study as well as the structure of a solar cell with a PSG layer. Solar-grade and monocrystalline Si wafers with a size and resistivity of 5 in 2 and 0.5-3.0 ·cm, respectively, were used in this study. These wafers were processed using the following procedures: texturization by using an alkaline solution, P diffusion by using POCl 3 as a precursor, removing PSG layers by using a dilute HF solution (for standard solar cells only), depositing SixNy films as antireflection coatings by using a plasma enhanced chemical vapor deposition, and forming front and rear contacts by performing screen-p...