Theoretical and experimental photovoltaic energy conversion in an organic film system

A theoretical model in which charge separation takes place at an electrode energy barrier has been extended to estimate the photvoltaic energy conversion efficiency as a function of film thickness and energy barrier for an organic film system based on the (1 : 1) PVK-TNF charge-transfer complex. The model predicts that the theoretical efficiency will be determined by space-charge-limited conduction for films of thickness greater than 0.1 μ. The efficiency is proportional to the inverse cube of the film thickness in this film thickness range. In the case of ultrathin films (0.1 μ), the model predicts that the efficiency will be determined by the photocarrier generation efficiency and can approach 1%. Experimental photovoltaic energy conversion efficiencies for films of thickness 5–25 μ are in agreement with the general features predicted by the model.