Enhanced efficiency in plastic solar cells via energy matched solution processed NiO _x interlayers

K. Xerxes Steirer, Paul F. Ndione, N. Edwin Widjonarko, Matthew T. Lloyd, Jens Meyer, Erin L. Ratcliff, Antoine Kahn, Neal R. Armstrong, Calvin J. Curtis, David S. Ginley, Joseph J. Berry, Dana C. Olson