Fig. 4. Impact of side-chain modification on the performance of BHJ organic solar cells.

a Chemical structure of Y6(OD) with side chains considerably large than Y6. b JV curves of the solar cells based on PBDB-T, PBDB-T(OD), mixed with Y6 and Y6(OD). $△V_{\mathrm{nr}}$ values, calculated from $V_{\mathrm{OC},\mathrm{rad}}$, are indicated. c TPV measurements performed on the solar cells based on the active materials with and without the side chain modification, the voltage decay lifetime values (left) are derived from the transient signals (right) of the solar cells measured under different steady-state illumination intensities (to generate different steady-state photovoltage, ($V_{\mathrm{ph}}$)). The dash lines in the left plot are a guide to the eyes, and details regarding the measurements are provided in Supplementary Note 7.