Disclosed herein are polycarbonate fibers and fibrous substrates, such as papers, containing such fibers. The polycarbonate fibers are produced from a polymeric composition comprising a cross-linkable polycarbonate containing endgroups derived from a monofunctional benzophenone or containing repeating units derived from a difunctional benzophenone. The polycarbonate fibers can be combined with other fibers to form the fibrous substrate. Upon exposure to ultraviolet light, crosslinking of the polycarbonate fibers will occur, improving various properties of the fibrous substrate.