At least a dozen existing technologies produce solar cells with overall power conversion efficiencies ranging from 5% to 40%. Given that these technologies are available, the question arises as to whether society should invest in research to develop even more new technologies, or just work to improve existing ones. At the University of Minnesota, my students and I work on a variety of research projects ranging from improving the reliability of existing solar cell technologies such as copper indium gallium diselenide to future thin film solar cells such as those based on copper zinc tin sulfide and quantum dots. Even though new technologies are uncertain, they are worth pursuing on the chance they may lead to even more efficient solar cells at much lower cost. In this talk, I will give an overview of the research projects in my group with emphasis on our recent results for copper indium gallium diselenide and copper zinc tin sulfide, a material that consists of abundant and nontoxic elements.