Heterojunction thin-film solar cells are usually fabricated from n-type window material (large bandgap) in its front and p-type absorber material (small bandgap) in the back. In this work, an inverted cell with p-type window material in front and a rear n-type absorber is presented. A diamond/CdTe photovoltaic cell has been fabricated to demonstrate the concept of an inverted p-n heterojunction solar cell. A systematic study of the influence of various experimental parameters on the behavior of the cell has been undertaken and is briefly discussed. It is shown that the solar cell open-circuit voltage V-OC is 230 mV with an internal quantum efficiency of 70% at 500 nm. Steps to further improve the photoresponse and the photovoltaic conversion efficiency of the cell are discussed.