Solution‐Processed Organic Solar Cells with High Open‐Circuit Voltage of 1.3 V and Low Non‐Radiative Voltage Loss of 0.16 V
Ning An, Yunhao Cai, Hongbo Wu, Ailing Tang, Kangning Zhang, Xiaotao Hao, Zaifei Ma, Qiang Guo, Hwa Sook Ryu, Han Young Woo, Yanming Sun, Erjun Zhou
Abstract
Abstract Compared with inorganic or perovskite solar cells, the relatively large non‐radiative recombination voltage losses (Δ V non‐rad ) in organic solar cells (OSCs) limit the improvement of the open‐circuit voltage ( V oc ). Herein, OSCs are fabricated by adopting two pairs of D–π–A polymers (PBT1‐C/PBT1‐C‐2Cl and PBDB‐T/PBDB‐T‐2Cl) as electron donors and a wide‐bandgap molecule BTA3 as the electron acceptor. In these blends, a charge‐transfer state energy ( E CT ) as high as 1.70–1.76 eV is achieved, leading to small energetic differences between the singlet excited states and charge‐transfer states (Δ E CT ≈ 0.1 eV). In addition, after introducing chlorine atoms into the π‐bridge or the side chain of benzodithiophene (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‐2Cl and PBDB‐T‐2Cl, respectively. Their corresponding Δ V non‐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 V oc of 1.3 V. The Δ V non‐rad of 0.16 V and V oc of 1.3 V achieved in PBT1‐C‐2Cl:BTA3 OSCs are thought to represent the best values for solution‐processed OSCs reported in the literature so far.