© 2019 Polish Academy of Sciences. All rights reserved.The photovoltaic energy is one of the most popular topics of research in the field of clean energy sources. It benefits directly from the sun, and has been accepted as a promising technology for the future. To this end, GaInP/GaInAs/Ge TJ solar cells, capable of being grown with the molecular beam epitaxy device, are designed along with tunnel junction layers. In this work, the analytical solar cell model is used for the calculation of solar cell performance. The calculation for the photo-response of the radiation spectrum of the solar cells includes an analytical solution equation in the model, including the continuity equations based on both the minority and majority carriers, the Poisson equation, and the current equation. For these calculations, Fortran programming language is used with high data sensitivity. The J, Voc, and η values of the GaInP/GaInAs/Ge TJ solar cell are calculated for the AM1.5G solar spectrum at temperatures in the range 200-450 K. The η of the solar cell at room temperature under 1 sun is calculated as 35.114%. As a result, triple or higher junction solar cell structures need to be designed in order to obtain greater efficiency.