The high photovoltage of PCE10:EH-IDTBR photocathodes also makes them promising candidates for the more challenging PEC CO2 reduction to CO. To demonstrate this product scope, OPV devices were next interfaced with a molecular cobalt porphyrin catalyst (Supplementary Fig. ), which was 31,33,38 Fig. | PEC performance of OPV photocathodes. a, Representative CV scans of H2 evolution and CO2 reduction photocathodes recorded at 10 mV s -1 under chopped and continuous 1 sun irradiation. The black arrow refers to the initial scanning direction. b, Long-term CA trace of an OPV|GE|Pt electrode recorded at 0 V vs. RHE. Pt re-deposition at 240 h is denoted by an asterisk. c, Cumulative amount of H2 produced and FY over 300 h of operation. d, Cumulative product amounts and FYs of an OPV|GE|CoMTPP@CNT photocathode at 0 V vs. RHE, under 0.1 sun with stirring. e, Light intensity and mass transport dependence of product formation over 4 h at 0 V vs. RHE. All experiments were conducted under simulated 1 sun irradiation (AM 1.5G, 100 mW cm -2 ) at room temperature, without stirring, in a 0.1 M KBi, 0.1 M K2SO4 buffer (pH 8.5) for H2 evolution and in a 0.5 M KHCO3 buffer (pH 7.4) for CO2 reduction, unless stated otherwise. f, Literature benchmarking comparing photocathode onset potential (Eonset) and initial photocurrent density (J0V,HER) recorded at 0 V vs. RHE for H2 evolution photocathodes (n.b., no reports describe OPV photocathodes for CO2 reduction). c, Cross-section SEM image of an OPV cell.