Dithienogermole‐Containing Small‐Molecule Solar Cells with 7.3% Efficiency: In‐Depth Study on the Effects of Heteroatom Substitution of Si with Ge |
| |
| Authors: | Mijin Moon Bright Walker Junghoon Lee Song Yi Park Hyungju Ahn Taehyo Kim Tack Ho Lee Jungwoo Heo Jung Hwa Seo Tae Joo Shin Jin Young Kim Changduk Yang |
| |
| Affiliation: | 1. Department of Energy Engineering, School of Energy and Chemical Engineering, Low Dimensional Carbon Materials Center, Ulsan National Institute of Science and Technology (UNIST), Ulsan, South Korea;2. Pohang Accelerator Laboratory, Pohang University of Science and Technology, Pohang, Kyungbuk, South Korea;3. Department of Materials Physics, Dong‐A University, Busan, Republic of Korea |
| |
| Abstract: | Two small molecule donor materials (DTGe(FBTTh2)2 and DTGe(FBTBFu)2) incorporating the dithienogermole (DTGe) moiety with fluorobenzothiadiazole (FBT) and bithiophene (Th2) or benzofuran (BFu) end‐capping groups are synthesized and their properties as donor materials in small molecule bulk heterojunction type (BHJ) solar cells are investigated. The DTGe(FBTTh2)2 with Th2 end groups shows outstanding solar cell characteristics with efficiencies up to 6.4% using a standard BHJ architecture and 7.3% using a ZnO optical spacer, while the BFu end‐capped DTGe(FBTBFu)2 has slightly wider band gaps and yields slightly higher open circuit voltage (VOC) at the expense of short circuit current (JSC) and fill factor (FF). In this study, the DTGe‐based molecules are systematically compared to the dithienosilole (DTSi)‐based analogues, which are currently among the highest power conversion efficiency (PCE) small molecule solar cell donor materials known. The JSC produced by the DTGe molecule is found to be similar to, or slightly higher than the Si analogue, despite similar absorption characteristics, however, the PCE is similar to the Si analogues due to small decreases in VOC and FF. This report marks the first small molecule BHJ based on a Ge‐containing heterocycle with PCE over 7%. |
| |
| Keywords: | bulk heterojunctions dithienogermole germanium heteroatoms solar cells |
|
|
