Thiophene copolymer for 1 V high open-circuit voltage semitransparent photovoltaic devices

Abstract

In this work, one new middle bandgap (1.63 eV) copolymer, PBDDTT-3TC, was prepared by copolymerization of benzodithiophenedione (BDD) and symmetric terthiophene (3TC) with two carboxylate substituents. Devices based on PBDDTT-3TC : ITIC (1.0 : 1.0, wt/wt) exhibit an electron mobility of 1.79 × 10⁻⁴ cm² V⁻¹ s⁻¹ and a hole mobility of 1.77 × 10⁻⁴ cm² V⁻¹ s⁻¹, indicating a more balanced charge transport (μ_h/μ_e = 0.99). The opaque PSC exhibits a high V_oc of 1.00 V and a PCE of 6.92% without any additive or thermal-annealing treatment and with 100 nm Ag as the cathode, and the as-cast semitransparent PSC with equal treatment and 15 nm Ag as the cathode shows a high V_oc of 0.99 V and a PCE of 6.15% with an average transmittance of 23.83% and an average visible transmittance of 19.16%. This work suggests the potential of PBDDTT-3TC:ITIC as an active layer for fabricating highly efficient semitransparent PSCs.