We report on the charge transport and injection phenomena of (E,E,E,E)-1,4-bis[(4-styryl)styryl]-2-methoxy-5-(2'-ethylhexoxy)benzene (MEH-OPV5) sandwiched between asymmetric contacts. The hole mobility of MEH-OPV5 was determined by means of transient electroluminescence. The steady-state current was injection-limited. The electric field and temperature dependence of the current were quantitatively described by a phenomenological injection model of thermally assisted charge-carrier tunneling in a one-dimensional chain of hopping sites. Furthermore, we report on the photovoltaic properties of thin-film photovoltaic cells on the basis of donor-acceptor heterojunctions. MEH-OPV5 and buckminster fullerene were used as the donor and acceptor materials, respectively. The emphasis was on the role of morphology in such devices. (C) 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2665-2673, 2003