A research team led by Prof. Erjun Zhou from the National Center for Nanoscience and Technology (NCNST) proposed a low non-radiative voltage loss of 0.16 V in solution-processed organic solar cells. This work was published in Advance Materials, entitled “Solution-Processed Organic Solar Cells with High Open-Circuit Voltage of 1.3 V and Low Non-Radiative Voltage Loss of 0.16 V” (https://onlinelibrary.wiley.com/doi/full/10.1002/adma.202002122).
Compared with inorganic or perovskite solar cells, the relatively large non-radiative recombination voltage losses (ΔVnon-rad) in organic solar cells (OSCs) limit the improvement of the open-circuit voltage (VOC). Zhou erjun et al. adopted two pairs of D–π–A polymer donors (PBT1-C, PBT1-C-2Cl, PBDB-T, and PBDB-T-2Cl) and a wide-bandgap acceptor BTA3 to systemically investigate the effect of chlorination on the ΔVnon-rad. In these blends, a charge-transfer state energy (ECT) as high as 1.70–1.76 eV is achieved, leading to small energetic differences between the singlet excited states and charge-transfer states (ΔECT≈0.1 eV). In addition, after introducing chlorine atoms into the π–bridge or the side chain of benzo–dithiophene (BDT) unit, electroluminescence external quantum efficiencies as high as 1.9×10-3 and 1.0×10-3 are realized in OSCs based on PBTI–C–Cl and PBDB–T–Cl, respectively. Their corresponding ΔVnon-rad are 0.16 and 0.17 V, which are lower than those of OSCs based on the analog polymers without a chlorine atom (0.21 and 0.24 V for PBT1–C and PBDB–T, respectively), resulting in high VOC of 1.3 V. The ΔVnon-rad of 0.16 V and VOC of 1.3 V achieved in PBT–C–Cl:BTA OSCs are thought to represent the best values for solution–processed OSCs reported in the literature so far.
This work was supported by the National Natural Science Foundation of China, the National Key Research and Development Program of China, the Strategic Priority Research Program of Chinese Academy of Sciences and so on.
Figure. non-radiative recombination voltage losses (ΔVnon-rad) and electroluminescence external quantum efficiency of chlorinated and non-chlorinated organic solar cells.