The present invention provides module structures and methods of manufacturing rigid or flexible photovoltaic modules employing thin film solar cells fabricated on flexible substrates, preferably on flexible metallic foil substrates. The solar cells may be Group IBIIIAVIA compound solar cells or amorphous silicon solar cells fabricated on thin stainless steel or aluminum alloy foils. In one embodiment, initially a solar cell string including two or more solar cells is formed by interconnecting the solar cells with conductive leads or ribbons. At least one bypass diode electrically connects conductive back surfaces of at least two solar cells. The bypass diode and the solar cells are encapsulated with support material and are packed with the protective shell such that the at least one bypass diode is placed between at least one solar cell and the bottom protective sheet. The bypass diode is thermally connected to the back conductive surface of one of the solar cells so that the back conductive surface of the solar cell functions as a heat sink.