Origin of reduced polaron recombination in organic semiconductor devices

作者：Carsten Deibel, Alexander Wagenpfahl, Vladimir Dyakonov · 发表于：Physical Review B · 年份：2009 · DOI：10.1103/physrevb.80.075203 · 被引用次数：165 · 研究领域：Organic Electronics and Photovoltaics、Conducting polymers and applications、Perovskite Materials and Applications

We propose a model to explain the reduced bimolecular recombination rate found in state-of-the-art bulk heterojunction solar cells. When compared to the Langevin recombination, the experimentally observed rate is one to four orders of magnitude lower but gets closer to the Langevin case for low temperatures. Our model considers the organic solar cell as device with carrier-concentration gradients, which form due to the electrode/blend/electrode device configuration. The resulting electron concentration under working conditions of a solar cell is higher at the cathode than at the anode and vice versa for holes. Therefore, the spatially dependent bimolecular recombination rate, proportional to the local product of electron and hole concentrations, is much lower as compared to the calculation of the recombination rate based on the extracted and thus averaged charge-carrier concentrations. We consider also the temperature dependence of the recombination rate, which can be described with our model.