Table 2.

Voltage loss values from the subgap $\mathrm{EQE}$ measurements for the BHJ solar cells based on PBDB-T and PBDB-T(OD) mixed with different acceptors.

	$V_{OC}$ (V)	$E_{CT}/E_g$a (eV)	$V_{loss}$b (V)	$V_{OC,rad}$c (V)	${\Delta V}_{nr}$d (V)	${\Delta V}_r$e (V)
PBDB-T:IT4F	0.71	1.40	0.69	1.15	0.44	0.25
PBDB-T(OD):IT4F	0.83	1.45	0.62	1.20	0.37	0.25
PBDB-T:ITIC	0.90	1.52	0.62	1.24	0.34	0.28
PBDB-T(OD):ITIC	0.99	1.56	0.57	1.27	0.28	0.29
PBDB-T:Y6	0.67	1.42	0.75	1.04	0.37	0.38
PBDB-T(OD):Y6	0.77	1.42	0.65	1.06	0.29	0.36
PBDB-T(OD):Y6(OD)	0.86	1.41	0.55	1.07	0.21	0.34

JV curves and the photovoltaic performance parameters of the solar cells are provided in Supplementary Note 9.

^a$E_{\mathrm{g}}$ instead of $E_{\mathrm{CT}}$ are listed for the solar cells based on Y6 and Y6(OD), details in Supplementary Note 5.

^bCalculated using eq.$V_{\mathrm{loss}}=E_{\mathrm{CT}}/q-V_{\mathrm{OC}}$, the method used to determine $E_{\mathrm{CT}}$ is provided in Supplementary Note 5.

^cCalculated from the radiative limit for the dark saturation current, details in Supplementary Note 6.

^dCalculated using eq. ${\Delta V}_{\mathrm{nr}}=V_{\mathrm{OC},\mathrm{rad}}-V_{\mathrm{OC}}$; ${\Delta V}_{nr}$ values are also verified by measuring ${\mathrm{EQE}}_{\mathrm{EL}}$, details in Supplementary Note 6.

^eCalculated using eq. ${\Delta V}_{\mathrm{r}}=V_{\mathrm{loss}}-{\Delta V}_{\mathrm{nr}}.$