Dual carrier-selective contact transition metal dichalcogenide solar cells

Transition metal dichalcogenide (TMD) solar cells are promising candidates for high-specific-power photovoltaics due to their strong light-matter interactions, such as their high absorption coefficients. The performance of many TMD solar devices is limited by recombination losses at the semiconductor and metal electrode interface. Recent studies with silicon and perovskite solar cells overcome this challenge by employing two carrier-selective contacts to improve carrier separation and collection. In this work, we design and demonstrate the first dual selective contact TMD solar cell with both electron and hole transport layers. Resembling inverted perovskite device architectures, this solar cell consists of a vertical-junction 10-nm-thick WS2 absorber layer, C60 electron-selective contact, and PTAA hole-selective contact. This photovoltaic device exhibits an AM1.5 G open-circuit voltage of 523 mV and a power conversion efficiency of 2.4%. We characterize the carrier dynamics in the dual selective contact solar cell, which include achieving balanced transport with symmetric carrier-selective contact conductance to achieve high fill factors. We demonstrate this by showing that S-shaped I–V curves can be eliminated through reducing the thickness of the low-conductance contact. From theoretical calculations, we find that the TMD carrier lifetime limits the open-circuit voltage of TMD solar cells. To move towards the voltage limit and achieve higher solar performance, we outline steps for improving the dual selective contact solar cell architecture.