Engineering the interconnecting layer for efficient inverted tandem polymer solar cells with absorption complementary fullerene and nonfullerene acceptors

Applying materials with complementary optical absorption spectra to construct tandem solar cell can fulfill further improvement of photovoltaic performance, since tandem solar cell can harvest more photons and enhance the open-circuit voltage of the devices. For tandem solar cells, an interconnecting layer (ICL), which physically and electrically connects the front and the rear subcells, is essential to minimize the energy losses. Herein, we adopt MoO₃/Ag/PFN-Br as interconnecting layer to join front subcell of PBDTBDD:PC₇₀BM and rear subcell of PTB7-Th:IEICO-4F for construction the inverted tandem solar cell with structure of ITO/TIPD/PBDTBDD:PC₇₀BM/MoO₃/Ag/PFN-Br/PTB7-Th:IEICO-4F/MoO₃/Al. The tandem devices demonstrate strong and wide light response in the wavelength between 300 and 1000 nm. A promising power conversion efficiency (PCE) of 9.74% has been achieved with an open circuit voltage (V_oc) of 1.503 V. The PCE of tandem cell is 41.36% higher than that (6.89%) of front subcell and 27.82% higher than that (7.62%) of rear subcell.