One of the parameters affecting the efficiency of photovoltaic (PV) modules and PV systems is the temperature. The factors that increase the temperature in PV modules cause loss of efficiency. In this study, experiments have been conducted with the aim of reducing the module temperature. For this purpose, four polycrystalline and four monocrystalline PV modules, all with the same features, were used. A pair of polycrystalline and monocrystalline modules were used as reference modules. The aim of this study is to reduce the operating temperature of the modules, while also decreasing the transient temperature fluctuations in the system, in order to prevent the loss of efficiency. For this reason, current, voltage and power values of PV modules have been examined and the relationship between these values and module temperature has been explained. As a result, temperature values were measured at 30-80°C in reference modules, 30-50°C in heat pipe modules, 30-37°C in modules using heat pipes and phase-changing material, and 30-66°C in modules using phase-changing material with flexible surfaces. If the PV module operating temperature is increased by 35°C, the module efficiency decreases by 10%. Heat pipe and PCM balance the temperature in PV/T/PCM monocrystalline and polycrystalline modules. In PV/T/PCM modules, efficiency loss caused by temperature increase is 1%. In addition, electrical energy is produced from the heat accumulated on the surface of the PV module by means of Thermoelectric Generator (TEG). When the temperature difference between the surfaces is 15°C, the naturally cooled TE provides 0.45V energy output, while the forced-cooled TEG provides 0.97V energy output. As the temperature gap between the surfaces increases, the voltage and current values of the TEG also increase. Briefly, TEG's power values increase up to 5W depending on the temperature gap between surfaces.