An organic photosensitive optoelectronic device comprising: two electrodes in superposed relation comprising an anode and a cathode; a photoactive region comprising at least one donor material and at least one acceptor material disposed between the two electrodes to form a donor-acceptor heterojunction, wherein the at least one acceptor material has a Lowest Unoccupied Molecular Orbital energy level (LUMO Acc) and a Highest Occupied Molecular Orbital energy level (HOMO Acc), and the at least one donor material has a Lowest Unoccupied Molecular Orbital energy level (LUMO don) and a Highest Occupied Molecular Orbital energy level (HOMO don); and an exciton-blocking electron filter disposed between the cathode and the at least one acceptor material, wherein the electron filter comprises a mixture comprising at least one cathode-side wide energy gap material and at least one electron conducting material, and wherein the at least one cathode-side wide energy gap material has: - a Lowest Unoccupied Molecular Orbital energy level (LUMO CS-WG) smaller than or equal to the LUMO Acc; - a Highest Occupied Molecular Orbital energy level (HOMO CS-WG) larger than, equal to, or within 0.3 eV smaller than the HOMO Acc; and - a HOMO CS-WG -LUMO CS-WG energy gap wider than a HOMO Acc -LUMO Acc energy gap; wherein the at least one electron conducting material has a Lowest Unoccupied Molecular Orbital energy level (LUMO EC) larger than, equal to, or within 0.2 eV smaller than the LUMO Acc; wherein a first HOMO or LUMO energy level is "smaller than" a second HOMO or LUMO energy level if the first HOMO or LUMO energy level is closer to the vacuum level than the second HOMO or LUMO energy level, a first HOMO or LUMO energy level is "larger than" than a second HOMO or LUMO energy level if the first HOMO or LUMO energy level is further from the vacuum level than the second HOMO or LUMO energy level, and two orbital energy levels are "equal to" one another if their energies match to the tenth decimal place; and wherein the mixture comprises the at least one cathode-side wide energy gap material and the at least one electron conducting material at a ratio ranging from 10:1 to 1:10 by volume. two electrodes in superposed relation comprising an anode and a cathode; a photoactive region comprising at least one donor material and at least one acceptor material disposed between the two electrodes to form a donor-acceptor heterojunction, wherein the at least one acceptor material has a Lowest Unoccupied Molecular Orbital energy level (LUMO Acc) and a Highest Occupied Molecular Orbital energy level (HOMO Acc), and the at least one donor material has a Lowest Unoccupied Molecular Orbital energy level (LUMO don) and a Highest Occupied Molecular Orbital energy level (HOMO don); and an exciton-blocking electron filter disposed between the cathode and the at least one acceptor material, wherein the electron filter comprises a mixture comprising at least one cathode-side wide energy gap material and at least one electron conducting material, and wherein the at least one cathode-side wide energy gap material has: - a Lowest Unoccupied Molecular Orbital energy level (LUMO CS-WG) smaller than or equal to the LUMO Acc; - a Highest Occupied Molecular Orbital energy level (HOMO CS-WG) larger than, equal to, or within 0.3 eV smaller than the HOMO Acc; and - a HOMO CS-WG -LUMO CS-WG energy gap wider than a HOMO Acc -LUMO Acc energy gap; - a Lowest Unoccupied Molecular Orbital energy level (LUMO CS-WG) smaller than or equal to the LUMO Acc; - a Highest Occupied Molecular Orbital energy level (HOMO CS-WG) larger than, equal to, or within 0.3 eV smaller than the HOMO Acc; and - a HOMO CS-WG -LUMO CS-WG energy gap wider than a HOMO Acc -LUMO Acc energy gap; wherein the at least one electron conducting material has a Lowest Unoccupied Molecular Orbital energy level (LUMO EC) larger than, equal to, or within 0.2 eV smaller than the LUMO Acc; wherein a first HOMO or LUMO energy level is "smaller than" a second HOMO or LUMO energy level if the first HOMO or LUMO energy level is closer to the vacuum level than the second HOMO or LUMO energy level, a first HOMO or LUMO energy level is "larger than" than a second HOMO or LUMO energy level if the first HOMO or LUMO energy level is further from the vacuum level than the second HOMO or LUMO energy level, and two orbital energy levels are "equal to" one another if their energies match to the tenth decimal place; and wherein the mixture comprises the at least one cathode-side wide energy gap material and the at least one electron conducting material at a ratio ranging from 10:1 to 1:10 by volume.