Perovskite as an effective V_oc switcher for high efficiency polymer solar cells

Highlights: • Phase dependent photocurrent generation and phase dependent charge transport is firstly observed in the MAPI/PDPP3T:PCBM parallel-like tandem solar cells. • The charge carriers generated in the MAPI change the V_oc and demonstrate the V_oc-switch effect of MAPI layer. • The introduction of MAPI to the BHJ solar cells leads to the reduction of thermalization loss and provides the potential to break the S-Q limit for single junction solar cells. In the perovskite/polymer based parallel-like tandem solar cell, the distinctive absorption spectra between the organic–inorganic halide perovskite absorber (CH₃NH₃PbI₃ (MAPI)) and poly-(diketopyrrolopyrrole-terthiophene) (PDPP3T) polymer absorber make it possible to investigate the electronic properties of charge carriers generated in either the perovskite or PDPP3T layer separately. The current density–voltage (J–V) curves of the device are measured under the monochromatic LED irradiation at significantly different wavelengths to confirm the charge carrier generated in MAPI offer higher V_oc. The voltage biased external quantum efficiency (EQE) measurement is employed to understand the charge transport mechanism in the system. The J–V curves and EQE data confirm that charge carriers generated by the photons absorbed in the perovskite layer or in PDPP3T behave independently. Compared with the bulk heterojunction structure, this parallel-like tandem structure increases V_oc while reducing thermalization loss, providing a possibility to break the traditional Shockley–Queisser (S–Q) limit set for single junction devices.