Enabling Transparent-Conductive-Oxide Free Efficient Heterojunction Solar Cells by Flexibly Using Dopant-Free Contact

Minimizing the optical parasitic absorption loss in hydrogenated amorphous silicon (a-Si:H) and transparent conductive oxide (TCO) layers is considered an effective approach to further improve the power conversion efficiencies (PCEs) of crystalline silicon heterojunction (SHJ) solar cells. In this work, carrier-selective passivating contacts for both polarities, e.g., alkali fluoride/aluminum electron-selective contact and transition metal oxide/silver hole-selective contact, are used to completely replace the doped a-Si:H layers in SHJ solar cell, forming a totally TCO- and dopant-free asymmetric structure. By minimizing the charge carrier transporting and recombination losses on the front-side electron-selective contact through interface engineering, an improved photovoltaic performance with a short-circuit current density of 40.5 mA cm(-2), an open-circuit voltage of 0.709 V, and a fill factor of 79.6% is realized, resulting in a final PCE exceeding 22.9%. The successful demonstration of this work provides an effective way to further boost the efficiency, as well as reduce the cost of SHJ solar cells with a TCO-free and doped a-Si:H-free configuration, using a moderate and simplified fabrication process.