Thermoelectric generators (TEGs) are devices that convert heat into electricity. They are very attractive energy harvesters because they are highly reliable and environment-friendly. The efficiency of thermoelectric generators depends on the temperature gradient across the device, the average temperature of operation, and on the thermoelectric properties of the material. Most work on improving the TEG efficiency deals with improving the thermoelectric properties of the material. In this work, we propose a method of improving the efficiency of the TEG by increasing the temperature gradient across the device. To accomplish this, a lens can be used to concentrate solar radiation on the membrane of the TEG. By focusing solar radiation, the input heat flux increases; the temperature gradient across the device also increases; and the efficiency of the TEG improves as well.