Browsing by Author "AMMAR AKHLAQ"

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    Evaluating the role of heterojunction tunneling diode and parameter optimization for efficiency enhancement in multijunction solar cell
    (UMT.Lahore, 2019) AMMAR AKHLAQ
    In the family of multijunction solar cells, the GaInP/GaAs/Ge triple-junction solar cells are the most proficient type of cell design. They enhance the performance of the solar cell by taking advantage of the combination of different high crystalline quality semiconductors. The high efficiency achieving capability of the multijunction solar cell largely depends on its structural composition. Due to the crucialness and bewildering complexities in the structural composition, the fabrication bases experimentation and optimization of multijunction solar cell is very expensive and time-consuming. In such a situation, parameter optimization and performance evaluation can be performed using numerical tools such as Silvaco Atlas. This work explores the physical model based on numerical modeling of triple-junction GaInP/GaAs/Ge solar cell in order to evaluate the role of heterojunction interface and parameter optimization in the efficiency enhancement. The optimization process has been carried out using a genetic algorithm. Whereas, the structure studied is developed within the framework of Silvaco Atlas. In the first stage of development, the performance of InGaP/GaAs cell has been examined and improved in three phases, in the first phase, the evaluation is carried out after the introduction of heterojunction tunneling diode. In this phase due to the use of optimized and suitable tunneling diode, the efficiency of GaInP/GaAs solar cell has been increased from 22 % to 25.40 %. In the second phase the improvement has been studied via parameter optimization of the cell layers. After parameter optimization the efficiency of the cell structure has increased to 28.63 %. In the third phase, the efficiency enhancement is analyzed after introducing the hetero-interface in a bottom cell together with the modified BSF layer. The alteration in the cell design has successively enhanced the performance of the GaInP/GaAs-AlInP cell. The modified cell with heterojunction subcell has achieved efficiency of 33.6 %. In the second stage of development, the bottom germanium subcell has been added to the structure in order to have a GaInP/GaAs-AlInP/Ge triple-junction solar cell. The final performance indicators of optimized cell has the value as follow, VOC is 2.68 V, ISC is 18.3 𝑚𝐴/c𝑚2. The maximum power out of the cell is recorded to be 47.1 mW/c𝑚2. Whereas, the fill factor of the cell is 93.5 % and the overall efficiency achieved by the cell is 34.6 %.