Overcoming Defect-Induced Charge Recombination Loss in Organic Solar Cells by Förster Resonance Energy Transfer

The strong charge recombination such as defect-induced recombination in some transition metal oxide interlayers is really existent, which has resulted in the severe charge loss and the deteriorated device performance. Herein, the improved performance of a device is demonstrated with an annealing-free ZnO:P3HT composite interlayer by minimizing the charge recombination loss. The P3HT incorporated in the ZnO interlayer can reuse the wasted energy from the defect-induced charge radiative recombination by Förster resonance energy transfer, which will reduce the charge recombination loss in the device. Meanwhile, the highest occupied molecular orbital of P3HT than ZnO, can work as the hole traps in the ZnO interlayer, which also contributes to the increased background electron density and improved electron conductivity. The reduced charge recombination loss and improved conductivity of the ZnO interlayer are beneficial to acquire a higher short-circuit current density of 17.78 mA/cm2 and fill factor of 74.47%, leading to an enhanced power conversion efficiency of 9.84%. Our study paves a new way to overcome the drawback of charge recombination loss by reusing the energy of charge radiative recombination, instead of suppressing the charge recombination in advance.