Exciton Fission Enhanced Silicon Solar Cell

Crystalline silicon (<i>c</i>-Si) photovoltaics, which currently comprise over 90% of the solar cell market, are also among the promising candidates for solar-to-chemical conversion such as water splitting and CO₂ reduction [1-3]. However, they are nearing the thermodynamic single junction limit, presenting significant challenges for further efficiency enhancements in <i>c</i>-Si photovoltaics. One promising method to exceed this limit involves sensitizing <i>c</i>-Si with organic molecules capable of singlet exciton fission (SF), a process that generates two triplet excitons (electron-hole pairs) from a single photon. Efficient transfer of these triplet excitons to <i>c</i>-Si could potentially enhance photocurrent and power conversion efficiency (PCE). Previous studies have shown coupling between <i>c</i>-Si and the archetypal SF material (tetracene), facilitated by passivating interfacial layers of hafnium oxynitride, as evidenced by magnetic-field-dependent photocurrent measurements [4]. However, the photovoltaic performance did not improve due to insufficient passivation and poor carrier extraction at the surface between tetracene and <i>c</i>-Si. We have developed a novel interfacial heterostructure that effectively passivates surface defects and facilitates intermediate charge separated states necessary for the transfer of triplet excitons from tetracene to <i>c</i>-Si. Utilizing <i>c</i>-Si solar cells with shallow p-n junctions and a microstructured geometry, we demonstrate, for the first time, enhancements in short-circuit current and PCE attributed to SF in tetracene.<br/><br/>[1] Reece, Steven Y., et al. "Wireless solar water splitting using silicon-based semiconductors and earth-abundant catalysts." science 334.6056 (2011): 645-648.<br/>[2] Jin, Wonjoo, et al. "Natural leaf-inspired solar water splitting system." Applied Catalysis B: Environmental 322 (2023): 122086.<br/>[3] Lee, Kangmin, et al. "Sunlight-activatable ROS generator for cell death using TiO2/c-Si microwires." Nano Letters 21.16 (2021): 6998-7004.<br/>[4] Einzinger, Markus, et al. "Sensitization of silicon by singlet exciton fission in tetracene." Nature 571.7763 (2019): 90-94.