Temperature dependence of open-circuit voltage in organic solar cells from generation–recombination kinetic balance

The variation in the open-circuit voltage of bulk-heterojunction organic solar cells with temperature and light intensity is analyzed based on the kinetic balance between photogeneration and recombination rates, by determining the Fermi level displacement with temperature and occupancy of the density-of-states. In good accordance with experimental observations, a negative temperature coefficient of order dVoc/dT≈−1 mV K−1 is obtained at temperatures higher than a critical value Tc, which signals the transition between high- to low-occupancy conditions. This temperature dependence is valid for carriers obeying Boltzmann statistics at low-occupancy level, in similarity to that occurring for inorganic solar cells.