[16a-A401-1~10] 12.5 Organic and hybrid solar cells

[16a-A401-6] What is the optimum bandgap of the organic materials for solar cells?

〇Hiroyuki Yoshida^1,2, Kyohei Nakano³, Ai Sugie⁴, Keisuke Tajima³, Itaru Osaka⁵ (1.Chiba Univ., 2.MCRC Chiba Univ., 3.RIKEN, 4.Chiba Univ., 5.Hiroshima Univ.)

Keywords:exciton binding energy, organic solar cell, bandgap

Strongly bound excitons causes the energy loss of organic solar cell. In this study, we precisely determine the exciton binding energy as the difference between the optical and transport bandgaps. Through a systematic comparison of a wide range of organic semiconductors including 15 non-fullerene acceptors, 4 fullerene acceptors, 13 low-bandgap polymers, and 7 organic light-emitting diode materials, we found that the exciton binding energy is one-quarter of the transport bandgap. By taking into account the bandgap dependence of the exciton binding energy, we predict that the optimum bandgap for the best power conversion efficiency is 0.2 to 0.3 eV smaller than previous predictions.